palladium/include/pd/external/stb_image.hpp

/* stb_image - v2.30 - public domain image loader - http://nothings.org/stb
                                  no warranty implied; use at your own risk

   Do this:
      #define PD_IMAGE_IMPLEMENTATION
   before you include this file in *one* C or C++ file to create the implementation.

   // i.e. it should look like this:
   #include ...
   #include ...
   #include ...
   #define PD_IMAGE_IMPLEMENTATION
   #include "stb_image.h"

   You can #define PDI_ASSERT(x) before the #include to avoid using assert.h.
   And #define PDI_MALLOC, PDI_REALLOC, and PDI_FREE to avoid using malloc,realloc,free


   QUICK NOTES:
      Primarily of interest to game developers and other people who can
          avoid problematic images and only need the trivial interface

      JPEG baseline & progressive (12 bpc/arithmetic not supported, same as stock IJG lib)
      PNG 1/2/4/8/16-bit-per-channel

      TGA (not sure what subset, if a subset)
      BMP non-1bpp, non-RLE
      PSD (composited view only, no extra channels, 8/16 bit-per-channel)

      GIF (*comp always reports as 4-channel)
      HDR (radiance rgbE format)
      PIC (Softimage PIC)
      PNM (PPM and PGM binary only)

      Animated GIF still needs a proper API, but here's one way to do it:
          http://gist.github.com/urraka/685d9a6340b26b830d49

      - decode from memory or through FILE (define PDI_NO_STDIO to remove code)
      - decode from arbitrary I/O callbacks
      - SIMD acceleration on x86/x64 (SSE2) and ARM (NEON)

   Full documentation under "DOCUMENTATION" below.


LICENSE

  See end of file for license information.

RECENT REVISION HISTORY:

      2.30  (2024-05-31) avoid erroneous gcc warning
      2.29  (2023-05-xx) optimizations
      2.28  (2023-01-29) many error fixes, security errors, just tons of stuff
      2.27  (2021-07-11) document pdi_info better, 16-bit PNM support, bug fixes
      2.26  (2020-07-13) many minor fixes
      2.25  (2020-02-02) fix warnings
      2.24  (2020-02-02) fix warnings; thread-local failure_reason and flip_vertically
      2.23  (2019-08-11) fix clang static analysis warning
      2.22  (2019-03-04) gif fixes, fix warnings
      2.21  (2019-02-25) fix typo in comment
      2.20  (2019-02-07) support utf8 filenames in Windows; fix warnings and platform ifdefs
      2.19  (2018-02-11) fix warning
      2.18  (2018-01-30) fix warnings
      2.17  (2018-01-29) bugfix, 1-bit BMP, 16-bitness query, fix warnings
      2.16  (2017-07-23) all functions have 16-bit variants; optimizations; bugfixes
      2.15  (2017-03-18) fix png-1,2,4; all Imagenet JPGs; no runtime SSE detection on GCC
      2.14  (2017-03-03) remove deprecated PDI_JPEG_OLD; fixes for Imagenet JPGs
      2.13  (2016-12-04) experimental 16-bit API, only for PNG so far; fixes
      2.12  (2016-04-02) fix typo in 2.11 PSD fix that caused crashes
      2.11  (2016-04-02) 16-bit PNGS; enable SSE2 in non-gcc x64
                         RGB-format JPEG; remove white matting in PSD;
                         allocate large structures on the stack;
                         correct channel count for PNG & BMP
      2.10  (2016-01-22) avoid warning introduced in 2.09
      2.09  (2016-01-16) 16-bit TGA; comments in PNM files; PDI_REALLOC_SIZED

   See end of file for full revision history.


 ============================    Contributors    =========================

 Image formats                          Extensions, features
    Sean Barrett (jpeg, png, bmp)          Jetro Lauha (pdi_info)
    Nicolas Schulz (hdr, psd)              Martin "SpartanJ" Golini (pdi_info)
    Jonathan Dummer (tga)                  James "moose2000" Brown (iPhone PNG)
    Jean-Marc Lienher (gif)                Ben "Disch" Wenger (io callbacks)
    Tom Seddon (pic)                       Omar Cornut (1/2/4-bit PNG)
    Thatcher Ulrich (psd)                  Nicolas Guillemot (vertical flip)
    Ken Miller (pgm, ppm)                  Richard Mitton (16-bit PSD)
    github:urraka (animated gif)           Junggon Kim (PNM comments)
    Christopher Forseth (animated gif)     Daniel Gibson (16-bit TGA)
                                           socks-the-fox (16-bit PNG)
                                           Jeremy Sawicki (handle all ImageNet JPGs)
 Optimizations & bugfixes                  Mikhail Morozov (1-bit BMP)
    Fabian "ryg" Giesen                    Anael Seghezzi (is-16-bit query)
    Arseny Kapoulkine                      Simon Breuss (16-bit PNM)
    John-Mark Allen
    Carmelo J Fdez-Aguera

 Bug & warning fixes
    Marc LeBlanc            David Woo          Guillaume George     Martins Mozeiko
    Christpher Lloyd        Jerry Jansson      Joseph Thomson       Blazej Dariusz Roszkowski
    Phil Jordan                                Dave Moore           Roy Eltham
    Hayaki Saito            Nathan Reed        Won Chun
    Luke Graham             Johan Duparc       Nick Verigakis       the Horde3D community
    Thomas Ruf              Ronny Chevalier                         github:rlyeh
    Janez Zemva             John Bartholomew   Michal Cichon        github:romigrou
    Jonathan Blow           Ken Hamada         Tero Hanninen        github:svdijk
    Eugene Golushkov        Laurent Gomila     Cort Stratton        github:snagar
    Aruelien Pocheville     Sergio Gonzalez    Thibault Reuille     github:Zelex
    Cass Everitt            Ryamond Barbiero                        github:grim210
    Paul Du Bois            Engin Manap        Aldo Culquicondor    github:sammyhw
    Philipp Wiesemann       Dale Weiler        Oriol Ferrer Mesia   github:phprus
    Josh Tobin              Neil Bickford      Matthew Gregan       github:poppolopoppo
    Julian Raschke          Gregory Mullen     Christian Floisand   github:darealshinji
    Baldur Karlsson         Kevin Schmidt      JR Smith             github:Michaelangel007
                            Brad Weinberger    Matvey Cherevko      github:mosra
    Luca Sas                Alexander Veselov  Zack Middleton       [reserved]
    Ryan C. Gordon          [reserved]                              [reserved]
                     DO NOT ADD YOUR NAME HERE

                     Jacko Dirks

  To add your name to the credits, pick a random blank space in the middle and fill it.
  80% of merge conflicts on stb PRs are due to people adding their name at the end
  of the credits.
*/

#ifndef PDI_INCLUDE_PD_IMAGE_H
#define PDI_INCLUDE_PD_IMAGE_H

// DOCUMENTATION
//
// Limitations:
//    - no 12-bit-per-channel JPEG
//    - no JPEGs with arithmetic coding
//    - GIF always returns *comp=4
//
// Basic usage (see HDR discussion below for HDR usage):
//    int x,y,n;
//    unsigned char *data = pdi_load(filename, &x, &y, &n, 0);
//    // ... process data if not NULL ...
//    // ... x = width, y = height, n = # 8-bit components per pixel ...
//    // ... replace '0' with '1'..'4' to force that many components per pixel
//    // ... but 'n' will always be the number that it would have been if you said 0
//    pdi_image_free(data);
//
// Standard parameters:
//    int *x                 -- outputs image width in pixels
//    int *y                 -- outputs image height in pixels
//    int *channels_in_file  -- outputs # of image components in image file
//    int desired_channels   -- if non-zero, # of image components requested in result
//
// The return value from an image loader is an 'unsigned char *' which points
// to the pixel data, or NULL on an allocation failure or if the image is
// corrupt or invalid. The pixel data consists of *y scanlines of *x pixels,
// with each pixel consisting of N interleaved 8-bit components; the first
// pixel pointed to is top-left-most in the image. There is no padding between
// image scanlines or between pixels, regardless of format. The number of
// components N is 'desired_channels' if desired_channels is non-zero, or
// *channels_in_file otherwise. If desired_channels is non-zero,
// *channels_in_file has the number of components that _would_ have been
// output otherwise. E.g. if you set desired_channels to 4, you will always
// get RGBA output, but you can check *channels_in_file to see if it's trivially
// opaque because e.g. there were only 3 channels in the source image.
//
// An output image with N components has the following components interleaved
// in this order in each pixel:
//
//     N=#comp     components
//       1           grey
//       2           grey, alpha
//       3           red, green, blue
//       4           red, green, blue, alpha
//
// If image loading fails for any reason, the return value will be NULL,
// and *x, *y, *channels_in_file will be unchanged. The function
// pdi_failure_reason() can be queried for an extremely brief, end-user
// unfriendly explanation of why the load failed. Define PDI_NO_FAILURE_STRINGS
// to avoid compiling these strings at all, and PDI_FAILURE_USERMSG to get slightly
// more user-friendly ones.
//
// Paletted PNG, BMP, GIF, and PIC images are automatically depalettized.
//
// To query the width, height and component count of an image without having to
// decode the full file, you can use the pdi_info family of functions:
//
//   int x,y,n,ok;
//   ok = pdi_info(filename, &x, &y, &n);
//   // returns ok=1 and sets x, y, n if image is a supported format,
//   // 0 otherwise.
//
// Note that stb_image pervasively uses ints in its public API for sizes,
// including sizes of memory buffers. This is now part of the API and thus
// hard to change without causing breakage. As a result, the various image
// loaders all have certain limits on image size; these differ somewhat
// by format but generally boil down to either just under 2GB or just under
// 1GB. When the decoded image would be larger than this, stb_image decoding
// will fail.
//
// Additionally, stb_image will reject image files that have any of their
// dimensions set to a larger value than the configurable PDI_MAX_DIMENSIONS,
// which defaults to 2**24 = 16777216 pixels. Due to the above memory limit,
// the only way to have an image with such dimensions load correctly
// is for it to have a rather extreme aspect ratio. Either way, the
// assumption here is that such larger images are likely to be malformed
// or malicious. If you do need to load an image with individual dimensions
// larger than that, and it still fits in the overall size limit, you can
// #define PDI_MAX_DIMENSIONS on your own to be something larger.
//
// ===========================================================================
//
// UNICODE:
//
//   If compiling for Windows and you wish to use Unicode filenames, compile
//   with
//       #define PDI_WINDOWS_UTF8
//   and pass utf8-encoded filenames. Call pdi_convert_wchar_to_utf8 to convert
//   Windows wchar_t filenames to utf8.
//
// ===========================================================================
//
// Philosophy
//
// stb libraries are designed with the following priorities:
//
//    1. easy to use
//    2. easy to maintain
//    3. good performance
//
// Sometimes I let "good performance" creep up in priority over "easy to maintain",
// and for best performance I may provide less-easy-to-use APIs that give higher
// performance, in addition to the easy-to-use ones. Nevertheless, it's important
// to keep in mind that from the standpoint of you, a client of this library,
// all you care about is #1 and #3, and stb libraries DO NOT emphasize #3 above all.
//
// Some secondary priorities arise directly from the first two, some of which
// provide more explicit reasons why performance can't be emphasized.
//
//    - Portable ("ease of use")
//    - Small source code footprint ("easy to maintain")
//    - No dependencies ("ease of use")
//
// ===========================================================================
//
// I/O callbacks
//
// I/O callbacks allow you to read from arbitrary sources, like packaged
// files or some other source. Data read from callbacks are processed
// through a small internal buffer (currently 128 bytes) to try to reduce
// overhead.
//
// The three functions you must define are "read" (reads some bytes of data),
// "skip" (skips some bytes of data), "eof" (reports if the stream is at the end).
//
// ===========================================================================
//
// SIMD support
//
// The JPEG decoder will try to automatically use SIMD kernels on x86 when
// supported by the compiler. For ARM Neon support, you must explicitly
// request it.
//
// (The old do-it-yourself SIMD API is no longer supported in the current
// code.)
//
// On x86, SSE2 will automatically be used when available based on a run-time
// test; if not, the generic C versions are used as a fall-back. On ARM targets,
// the typical path is to have separate builds for NEON and non-NEON devices
// (at least this is true for iOS and Android). Therefore, the NEON support is
// toggled by a build flag: define PDI_NEON to get NEON loops.
//
// If for some reason you do not want to use any of SIMD code, or if
// you have issues compiling it, you can disable it entirely by
// defining PDI_NO_SIMD.
//
// ===========================================================================
//
// HDR image support   (disable by defining PDI_NO_HDR)
//
// stb_image supports loading HDR images in general, and currently the Radiance
// .HDR file format specifically. You can still load any file through the existing
// interface; if you attempt to load an HDR file, it will be automatically remapped
// to LDR, assuming gamma 2.2 and an arbitrary scale factor defaulting to 1;
// both of these constants can be reconfigured through this interface:
//
//     pdi_hdr_to_ldr_gamma(2.2f);
//     pdi_hdr_to_ldr_scale(1.0f);
//
// (note, do not use _inverse_ constants; pdi_image will invert them
// appropriately).
//
// Additionally, there is a new, parallel interface for loading files as
// (linear) floats to preserve the full dynamic range:
//
//    float *data = pdi_loadf(filename, &x, &y, &n, 0);
//
// If you load LDR images through this interface, those images will
// be promoted to floating point values, run through the inverse of
// constants corresponding to the above:
//
//     pdi_ldr_to_hdr_scale(1.0f);
//     pdi_ldr_to_hdr_gamma(2.2f);
//
// Finally, given a filename (or an open file or memory block--see header
// file for details) containing image data, you can query for the "most
// appropriate" interface to use (that is, whether the image is HDR or
// not), using:
//
//     pdi_is_hdr(char *filename);
//
// ===========================================================================
//
// iPhone PNG support:
//
// We optionally support converting iPhone-formatted PNGs (which store
// premultiplied BGRA) back to RGB, even though they're internally encoded
// differently. To enable this conversion, call
// pdi_convert_iphone_png_to_rgb(1).
//
// Call pdi_set_unpremultiply_on_load(1) as well to force a divide per
// pixel to remove any premultiplied alpha *only* if the image file explicitly
// says there's premultiplied data (currently only happens in iPhone images,
// and only if iPhone convert-to-rgb processing is on).
//
// ===========================================================================
//
// ADDITIONAL CONFIGURATION
//
//  - You can suppress implementation of any of the decoders to reduce
//    your code footprint by #defining one or more of the following
//    symbols before creating the implementation.
//
//        PDI_NO_JPEG
//        PDI_NO_PNG
//        PDI_NO_BMP
//        PDI_NO_PSD
//        PDI_NO_TGA
//        PDI_NO_GIF
//        PDI_NO_HDR
//        PDI_NO_PIC
//        PDI_NO_PNM   (.ppm and .pgm)
//
//  - You can request *only* certain decoders and suppress all other ones
//    (this will be more forward-compatible, as addition of new decoders
//    doesn't require you to disable them explicitly):
//
//        PDI_ONLY_JPEG
//        PDI_ONLY_PNG
//        PDI_ONLY_BMP
//        PDI_ONLY_PSD
//        PDI_ONLY_TGA
//        PDI_ONLY_GIF
//        PDI_ONLY_HDR
//        PDI_ONLY_PIC
//        PDI_ONLY_PNM   (.ppm and .pgm)
//
//   - If you use PDI_NO_PNG (or _ONLY_ without PNG), and you still
//     want the zlib decoder to be available, #define PDI_SUPPORT_ZLIB
//
//  - If you define PDI_MAX_DIMENSIONS, stb_image will reject images greater
//    than that size (in either width or height) without further processing.
//    This is to let programs in the wild set an upper bound to prevent
//    denial-of-service attacks on untrusted data, as one could generate a
//    valid image of gigantic dimensions and force stb_image to allocate a
//    huge block of memory and spend disproportionate time decoding it. By
//    default this is set to (1 << 24), which is 16777216, but that's still
//    very big.

#ifndef PDI_NO_STDIO
#include <stdio.h>
#endif // PDI_NO_STDIO

#define PDI_VERSION 1

enum
{
   PDI_default = 0, // only used for desired_channels

   PDI_grey       = 1,
   PDI_grey_alpha = 2,
   PDI_rgb        = 3,
   PDI_rgb_alpha  = 4
};

#include <stdlib.h>
typedef unsigned char pdi_uc;
typedef unsigned short pdi_us;

#ifdef __cplusplus
extern "C" {
#endif

#ifndef PDIDEF
#ifdef PD_IMAGE_STATIC
#define PDIDEF static
#else
#define PDIDEF extern
#endif
#endif

//////////////////////////////////////////////////////////////////////////////
//
// PRIMARY API - works on images of any type
//

//
// load image by filename, open file, or memory buffer
//

typedef struct
{
   int      (*read)  (void *user,char *data,int size);   // fill 'data' with 'size' bytes.  return number of bytes actually read
   void     (*skip)  (void *user,int n);                 // skip the next 'n' bytes, or 'unget' the last -n bytes if negative
   int      (*eof)   (void *user);                       // returns nonzero if we are at end of file/data
} pdi_io_callbacks;

////////////////////////////////////
//
// 8-bits-per-channel interface
//

PDIDEF pdi_uc *pdi_load_from_memory   (pdi_uc           const *buffer, int len   , int *x, int *y, int *channels_in_file, int desired_channels);
PDIDEF pdi_uc *pdi_load_from_callbacks(pdi_io_callbacks const *clbk  , void *user, int *x, int *y, int *channels_in_file, int desired_channels);

#ifndef PDI_NO_STDIO
PDIDEF pdi_uc *pdi_load            (char const *filename, int *x, int *y, int *channels_in_file, int desired_channels);
PDIDEF pdi_uc *pdi_load_from_file  (FILE *f, int *x, int *y, int *channels_in_file, int desired_channels);
// for pdi_load_from_file, file pointer is left pointing immediately after image
#endif

#ifndef PDI_NO_GIF
PDIDEF pdi_uc *pdi_load_gif_from_memory(pdi_uc const *buffer, int len, int **delays, int *x, int *y, int *z, int *comp, int req_comp);
#endif

#ifdef PDI_WINDOWS_UTF8
PDIDEF int pdi_convert_wchar_to_utf8(char *buffer, size_t bufferlen, const wchar_t* input);
#endif

////////////////////////////////////
//
// 16-bits-per-channel interface
//

PDIDEF pdi_us *pdi_load_16_from_memory   (pdi_uc const *buffer, int len, int *x, int *y, int *channels_in_file, int desired_channels);
PDIDEF pdi_us *pdi_load_16_from_callbacks(pdi_io_callbacks const *clbk, void *user, int *x, int *y, int *channels_in_file, int desired_channels);

#ifndef PDI_NO_STDIO
PDIDEF pdi_us *pdi_load_16          (char const *filename, int *x, int *y, int *channels_in_file, int desired_channels);
PDIDEF pdi_us *pdi_load_from_file_16(FILE *f, int *x, int *y, int *channels_in_file, int desired_channels);
#endif

////////////////////////////////////
//
// float-per-channel interface
//
#ifndef PDI_NO_LINEAR
   PDIDEF float *pdi_loadf_from_memory     (pdi_uc const *buffer, int len, int *x, int *y, int *channels_in_file, int desired_channels);
   PDIDEF float *pdi_loadf_from_callbacks  (pdi_io_callbacks const *clbk, void *user, int *x, int *y,  int *channels_in_file, int desired_channels);

   #ifndef PDI_NO_STDIO
   PDIDEF float *pdi_loadf            (char const *filename, int *x, int *y, int *channels_in_file, int desired_channels);
   PDIDEF float *pdi_loadf_from_file  (FILE *f, int *x, int *y, int *channels_in_file, int desired_channels);
   #endif
#endif

#ifndef PDI_NO_HDR
   PDIDEF void   pdi_hdr_to_ldr_gamma(float gamma);
   PDIDEF void   pdi_hdr_to_ldr_scale(float scale);
#endif // PDI_NO_HDR

#ifndef PDI_NO_LINEAR
   PDIDEF void   pdi_ldr_to_hdr_gamma(float gamma);
   PDIDEF void   pdi_ldr_to_hdr_scale(float scale);
#endif // PDI_NO_LINEAR

// pdi_is_hdr is always defined, but always returns false if PDI_NO_HDR
PDIDEF int    pdi_is_hdr_from_callbacks(pdi_io_callbacks const *clbk, void *user);
PDIDEF int    pdi_is_hdr_from_memory(pdi_uc const *buffer, int len);
#ifndef PDI_NO_STDIO
PDIDEF int      pdi_is_hdr          (char const *filename);
PDIDEF int      pdi_is_hdr_from_file(FILE *f);
#endif // PDI_NO_STDIO


// get a VERY brief reason for failure
// on most compilers (and ALL modern mainstream compilers) this is threadsafe
PDIDEF const char *pdi_failure_reason  (void);

// free the loaded image -- this is just free()
PDIDEF void     pdi_image_free      (void *retval_from_pdi_load);

// get image dimensions & components without fully decoding
PDIDEF int      pdi_info_from_memory(pdi_uc const *buffer, int len, int *x, int *y, int *comp);
PDIDEF int      pdi_info_from_callbacks(pdi_io_callbacks const *clbk, void *user, int *x, int *y, int *comp);
PDIDEF int      pdi_is_16_bit_from_memory(pdi_uc const *buffer, int len);
PDIDEF int      pdi_is_16_bit_from_callbacks(pdi_io_callbacks const *clbk, void *user);

#ifndef PDI_NO_STDIO
PDIDEF int      pdi_info               (char const *filename,     int *x, int *y, int *comp);
PDIDEF int      pdi_info_from_file     (FILE *f,                  int *x, int *y, int *comp);
PDIDEF int      pdi_is_16_bit          (char const *filename);
PDIDEF int      pdi_is_16_bit_from_file(FILE *f);
#endif



// for image formats that explicitly notate that they have premultiplied alpha,
// we just return the colors as stored in the file. set this flag to force
// unpremultiplication. results are undefined if the unpremultiply overflow.
PDIDEF void pdi_set_unpremultiply_on_load(int flag_true_if_should_unpremultiply);

// indicate whether we should process iphone images back to canonical format,
// or just pass them through "as-is"
PDIDEF void pdi_convert_iphone_png_to_rgb(int flag_true_if_should_convert);

// flip the image vertically, so the first pixel in the output array is the bottom left
PDIDEF void pdi_set_flip_vertically_on_load(int flag_true_if_should_flip);

// as above, but only applies to images loaded on the thread that calls the function
// this function is only available if your compiler supports thread-local variables;
// calling it will fail to link if your compiler doesn't
PDIDEF void pdi_set_unpremultiply_on_load_thread(int flag_true_if_should_unpremultiply);
PDIDEF void pdi_convert_iphone_png_to_rgb_thread(int flag_true_if_should_convert);
PDIDEF void pdi_set_flip_vertically_on_load_thread(int flag_true_if_should_flip);

// ZLIB client - used by PNG, available for other purposes

PDIDEF char *pdi_zlib_decode_malloc_guesssize(const char *buffer, int len, int initial_size, int *outlen);
PDIDEF char *pdi_zlib_decode_malloc_guesssize_headerflag(const char *buffer, int len, int initial_size, int *outlen, int parse_header);
PDIDEF char *pdi_zlib_decode_malloc(const char *buffer, int len, int *outlen);
PDIDEF int   pdi_zlib_decode_buffer(char *obuffer, int olen, const char *ibuffer, int ilen);

PDIDEF char *pdi_zlib_decode_noheader_malloc(const char *buffer, int len, int *outlen);
PDIDEF int   pdi_zlib_decode_noheader_buffer(char *obuffer, int olen, const char *ibuffer, int ilen);


#ifdef __cplusplus
}
#endif

//
//
////   end header file   /////////////////////////////////////////////////////
#endif // PDI_INCLUDE_PD_IMAGE_H

#ifdef PD_IMAGE_IMPLEMENTATION

#if defined(PDI_ONLY_JPEG) || defined(PDI_ONLY_PNG) || defined(PDI_ONLY_BMP) \
  || defined(PDI_ONLY_TGA) || defined(PDI_ONLY_GIF) || defined(PDI_ONLY_PSD) \
  || defined(PDI_ONLY_HDR) || defined(PDI_ONLY_PIC) || defined(PDI_ONLY_PNM) \
  || defined(PDI_ONLY_ZLIB)
   #ifndef PDI_ONLY_JPEG
   #define PDI_NO_JPEG
   #endif
   #ifndef PDI_ONLY_PNG
   #define PDI_NO_PNG
   #endif
   #ifndef PDI_ONLY_BMP
   #define PDI_NO_BMP
   #endif
   #ifndef PDI_ONLY_PSD
   #define PDI_NO_PSD
   #endif
   #ifndef PDI_ONLY_TGA
   #define PDI_NO_TGA
   #endif
   #ifndef PDI_ONLY_GIF
   #define PDI_NO_GIF
   #endif
   #ifndef PDI_ONLY_HDR
   #define PDI_NO_HDR
   #endif
   #ifndef PDI_ONLY_PIC
   #define PDI_NO_PIC
   #endif
   #ifndef PDI_ONLY_PNM
   #define PDI_NO_PNM
   #endif
#endif

#if defined(PDI_NO_PNG) && !defined(PDI_SUPPORT_ZLIB) && !defined(PDI_NO_ZLIB)
#define PDI_NO_ZLIB
#endif


#include <stdarg.h>
#include <stddef.h> // ptrdiff_t on osx
#include <stdlib.h>
#include <string.h>
#include <limits.h>

#if !defined(PDI_NO_LINEAR) || !defined(PDI_NO_HDR)
#include <math.h>  // ldexp, pow
#endif

#ifndef PDI_NO_STDIO
#include <stdio.h>
#endif

#ifndef PDI_ASSERT
#include <assert.h>
#define PDI_ASSERT(x) assert(x)
#endif

#ifdef __cplusplus
#define PDI_EXTERN extern "C"
#else
#define PDI_EXTERN extern
#endif


#ifndef _MSC_VER
   #ifdef __cplusplus
   #define pdi_inline inline
   #else
   #define pdi_inline
   #endif
#else
   #define pdi_inline __forceinline
#endif

#ifndef PDI_NO_THREAD_LOCALS
   #if defined(__cplusplus) &&  __cplusplus >= 201103L
      #define PDI_THREAD_LOCAL       thread_local
   #elif defined(__GNUC__) && __GNUC__ < 5
      #define PDI_THREAD_LOCAL       __thread
   #elif defined(_MSC_VER)
      #define PDI_THREAD_LOCAL       __declspec(thread)
   #elif defined (__STDC_VERSION__) && __STDC_VERSION__ >= 201112L && !defined(__STDC_NO_THREADS__)
      #define PDI_THREAD_LOCAL       _Thread_local
   #endif

   #ifndef PDI_THREAD_LOCAL
      #if defined(__GNUC__)
        #define PDI_THREAD_LOCAL       __thread
      #endif
   #endif
#endif

#if defined(_MSC_VER) || defined(__SYMBIAN32__)
typedef unsigned short pdi__uint16;
typedef   signed short pdi__int16;
typedef unsigned int   pdi__uint32;
typedef   signed int   pdi__int32;
#else
#include <stdint.h>
typedef uint16_t pdi__uint16;
typedef int16_t  pdi__int16;
typedef uint32_t pdi__uint32;
typedef int32_t  pdi__int32;
#endif

// should produce compiler error if size is wrong
typedef unsigned char validate_uint32[sizeof(pdi__uint32)==4 ? 1 : -1];

#ifdef _MSC_VER
#define PDI_NOTUSED(v)  (void)(v)
#else
#define PDI_NOTUSED(v)  (void)sizeof(v)
#endif

#ifdef _MSC_VER
#define PDI_HAS_LROTL
#endif

#ifdef PDI_HAS_LROTL
   #define pdi_lrot(x,y)  _lrotl(x,y)
#else
   #define pdi_lrot(x,y)  (((x) << (y)) | ((x) >> (-(y) & 31)))
#endif

#if defined(PDI_MALLOC) && defined(PDI_FREE) && (defined(PDI_REALLOC) || defined(PDI_REALLOC_SIZED))
// ok
#elif !defined(PDI_MALLOC) && !defined(PDI_FREE) && !defined(PDI_REALLOC) && !defined(PDI_REALLOC_SIZED)
// ok
#else
#error "Must define all or none of PDI_MALLOC, PDI_FREE, and PDI_REALLOC (or PDI_REALLOC_SIZED)."
#endif

#ifndef PDI_MALLOC
#define PDI_MALLOC(sz)           malloc(sz)
#define PDI_REALLOC(p,newsz)     realloc(p,newsz)
#define PDI_FREE(p)              free(p)
#endif

#ifndef PDI_REALLOC_SIZED
#define PDI_REALLOC_SIZED(p,oldsz,newsz) PDI_REALLOC(p,newsz)
#endif

// x86/x64 detection
#if defined(__x86_64__) || defined(_M_X64)
#define PDI__X64_TARGET
#elif defined(__i386) || defined(_M_IX86)
#define PDI__X86_TARGET
#endif

#if defined(__GNUC__) && defined(PDI__X86_TARGET) && !defined(__SSE2__) && !defined(PDI_NO_SIMD)
// gcc doesn't support sse2 intrinsics unless you compile with -msse2,
// which in turn means it gets to use SSE2 everywhere. This is unfortunate,
// but previous attempts to provide the SSE2 functions with runtime
// detection caused numerous issues. The way architecture extensions are
// exposed in GCC/Clang is, sadly, not really suited for one-file libs.
// New behavior: if compiled with -msse2, we use SSE2 without any
// detection; if not, we don't use it at all.
#define PDI_NO_SIMD
#endif

#if defined(__MINGW32__) && defined(PDI__X86_TARGET) && !defined(PDI_MINGW_ENABLE_SSE2) && !defined(PDI_NO_SIMD)
// Note that __MINGW32__ doesn't actually mean 32-bit, so we have to avoid PDI__X64_TARGET
//
// 32-bit MinGW wants ESP to be 16-byte aligned, but this is not in the
// Windows ABI and VC++ as well as Windows DLLs don't maintain that invariant.
// As a result, enabling SSE2 on 32-bit MinGW is dangerous when not
// simultaneously enabling "-mstackrealign".
//
// See https://github.com/nothings/stb/issues/81 for more information.
//
// So default to no SSE2 on 32-bit MinGW. If you've read this far and added
// -mstackrealign to your build settings, feel free to #define PDI_MINGW_ENABLE_SSE2.
#define PDI_NO_SIMD
#endif

#if !defined(PDI_NO_SIMD) && (defined(PDI__X86_TARGET) || defined(PDI__X64_TARGET))
#define PDI_SSE2
#include <emmintrin.h>

#ifdef _MSC_VER

#if _MSC_VER >= 1400  // not VC6
#include <intrin.h> // __cpuid
static int pdi__cpuid3(void)
{
   int info[4];
   __cpuid(info,1);
   return info[3];
}
#else
static int pdi__cpuid3(void)
{
   int res;
   __asm {
      mov  eax,1
      cpuid
      mov  res,edx
   }
   return res;
}
#endif

#define PDI_SIMD_ALIGN(type, name) __declspec(align(16)) type name

#if !defined(PDI_NO_JPEG) && defined(PDI_SSE2)
static int pdi__sse2_available(void)
{
   int info3 = pdi__cpuid3();
   return ((info3 >> 26) & 1) != 0;
}
#endif

#else // assume GCC-style if not VC++
#define PDI_SIMD_ALIGN(type, name) type name __attribute__((aligned(16)))

#if !defined(PDI_NO_JPEG) && defined(PDI_SSE2)
static int pdi__sse2_available(void)
{
   // If we're even attempting to compile this on GCC/Clang, that means
   // -msse2 is on, which means the compiler is allowed to use SSE2
   // instructions at will, and so are we.
   return 1;
}
#endif

#endif
#endif

// ARM NEON
#if defined(PDI_NO_SIMD) && defined(PDI_NEON)
#undef PDI_NEON
#endif

#ifdef PDI_NEON
#include <arm_neon.h>
#ifdef _MSC_VER
#define PDI_SIMD_ALIGN(type, name) __declspec(align(16)) type name
#else
#define PDI_SIMD_ALIGN(type, name) type name __attribute__((aligned(16)))
#endif
#endif

#ifndef PDI_SIMD_ALIGN
#define PDI_SIMD_ALIGN(type, name) type name
#endif

#ifndef PDI_MAX_DIMENSIONS
#define PDI_MAX_DIMENSIONS (1 << 24)
#endif

///////////////////////////////////////////////
//
//  pdi__context struct and start_xxx functions

// pdi__context structure is our basic context used by all images, so it
// contains all the IO context, plus some basic image information
typedef struct
{
   pdi__uint32 img_x, img_y;
   int img_n, img_out_n;

   pdi_io_callbacks io;
   void *io_user_data;

   int read_from_callbacks;
   int buflen;
   pdi_uc buffer_start[128];
   int callback_already_read;

   pdi_uc *img_buffer, *img_buffer_end;
   pdi_uc *img_buffer_original, *img_buffer_original_end;
} pdi__context;


static void pdi__refill_buffer(pdi__context *s);

// initialize a memory-decode context
static void pdi__start_mem(pdi__context *s, pdi_uc const *buffer, int len)
{
   s->io.read = NULL;
   s->read_from_callbacks = 0;
   s->callback_already_read = 0;
   s->img_buffer = s->img_buffer_original = (pdi_uc *) buffer;
   s->img_buffer_end = s->img_buffer_original_end = (pdi_uc *) buffer+len;
}

// initialize a callback-based context
static void pdi__start_callbacks(pdi__context *s, pdi_io_callbacks *c, void *user)
{
   s->io = *c;
   s->io_user_data = user;
   s->buflen = sizeof(s->buffer_start);
   s->read_from_callbacks = 1;
   s->callback_already_read = 0;
   s->img_buffer = s->img_buffer_original = s->buffer_start;
   pdi__refill_buffer(s);
   s->img_buffer_original_end = s->img_buffer_end;
}

#ifndef PDI_NO_STDIO

static int pdi__stdio_read(void *user, char *data, int size)
{
   return (int) fread(data,1,size,(FILE*) user);
}

static void pdi__stdio_skip(void *user, int n)
{
   int ch;
   fseek((FILE*) user, n, SEEK_CUR);
   ch = fgetc((FILE*) user);  /* have to read a byte to reset feof()'s flag */
   if (ch != EOF) {
      ungetc(ch, (FILE *) user);  /* push byte back onto stream if valid. */
   }
}

static int pdi__stdio_eof(void *user)
{
   return feof((FILE*) user) || ferror((FILE *) user);
}

static pdi_io_callbacks pdi__stdio_callbacks =
{
   pdi__stdio_read,
   pdi__stdio_skip,
   pdi__stdio_eof,
};

static void pdi__start_file(pdi__context *s, FILE *f)
{
   pdi__start_callbacks(s, &pdi__stdio_callbacks, (void *) f);
}

//static void stop_file(pdi__context *s) { }

#endif // !PDI_NO_STDIO

static void pdi__rewind(pdi__context *s)
{
   // conceptually rewind SHOULD rewind to the beginning of the stream,
   // but we just rewind to the beginning of the initial buffer, because
   // we only use it after doing 'test', which only ever looks at at most 92 bytes
   s->img_buffer = s->img_buffer_original;
   s->img_buffer_end = s->img_buffer_original_end;
}

enum
{
   PDI_ORDER_RGB,
   PDI_ORDER_BGR
};

typedef struct
{
   int bits_per_channel;
   int num_channels;
   int channel_order;
} pdi__result_info;

#ifndef PDI_NO_JPEG
static int      pdi__jpeg_test(pdi__context *s);
static void    *pdi__jpeg_load(pdi__context *s, int *x, int *y, int *comp, int req_comp, pdi__result_info *ri);
static int      pdi__jpeg_info(pdi__context *s, int *x, int *y, int *comp);
#endif

#ifndef PDI_NO_PNG
static int      pdi__png_test(pdi__context *s);
static void    *pdi__png_load(pdi__context *s, int *x, int *y, int *comp, int req_comp, pdi__result_info *ri);
static int      pdi__png_info(pdi__context *s, int *x, int *y, int *comp);
static int      pdi__png_is16(pdi__context *s);
#endif

#ifndef PDI_NO_BMP
static int      pdi__bmp_test(pdi__context *s);
static void    *pdi__bmp_load(pdi__context *s, int *x, int *y, int *comp, int req_comp, pdi__result_info *ri);
static int      pdi__bmp_info(pdi__context *s, int *x, int *y, int *comp);
#endif

#ifndef PDI_NO_TGA
static int      pdi__tga_test(pdi__context *s);
static void    *pdi__tga_load(pdi__context *s, int *x, int *y, int *comp, int req_comp, pdi__result_info *ri);
static int      pdi__tga_info(pdi__context *s, int *x, int *y, int *comp);
#endif

#ifndef PDI_NO_PSD
static int      pdi__psd_test(pdi__context *s);
static void    *pdi__psd_load(pdi__context *s, int *x, int *y, int *comp, int req_comp, pdi__result_info *ri, int bpc);
static int      pdi__psd_info(pdi__context *s, int *x, int *y, int *comp);
static int      pdi__psd_is16(pdi__context *s);
#endif

#ifndef PDI_NO_HDR
static int      pdi__hdr_test(pdi__context *s);
static float   *pdi__hdr_load(pdi__context *s, int *x, int *y, int *comp, int req_comp, pdi__result_info *ri);
static int      pdi__hdr_info(pdi__context *s, int *x, int *y, int *comp);
#endif

#ifndef PDI_NO_PIC
static int      pdi__pic_test(pdi__context *s);
static void    *pdi__pic_load(pdi__context *s, int *x, int *y, int *comp, int req_comp, pdi__result_info *ri);
static int      pdi__pic_info(pdi__context *s, int *x, int *y, int *comp);
#endif

#ifndef PDI_NO_GIF
static int      pdi__gif_test(pdi__context *s);
static void    *pdi__gif_load(pdi__context *s, int *x, int *y, int *comp, int req_comp, pdi__result_info *ri);
static void    *pdi__load_gif_main(pdi__context *s, int **delays, int *x, int *y, int *z, int *comp, int req_comp);
static int      pdi__gif_info(pdi__context *s, int *x, int *y, int *comp);
#endif

#ifndef PDI_NO_PNM
static int      pdi__pnm_test(pdi__context *s);
static void    *pdi__pnm_load(pdi__context *s, int *x, int *y, int *comp, int req_comp, pdi__result_info *ri);
static int      pdi__pnm_info(pdi__context *s, int *x, int *y, int *comp);
static int      pdi__pnm_is16(pdi__context *s);
#endif

static
#ifdef PDI_THREAD_LOCAL
PDI_THREAD_LOCAL
#endif
const char *pdi__g_failure_reason;

PDIDEF const char *pdi_failure_reason(void)
{
   return pdi__g_failure_reason;
}

#ifndef PDI_NO_FAILURE_STRINGS
static int pdi__err(const char *str)
{
   pdi__g_failure_reason = str;
   return 0;
}
#endif

static void *pdi__malloc(size_t size)
{
    return PDI_MALLOC(size);
}

// stb_image uses ints pervasively, including for offset calculations.
// therefore the largest decoded image size we can support with the
// current code, even on 64-bit targets, is INT_MAX. this is not a
// significant limitation for the intended use case.
//
// we do, however, need to make sure our size calculations don't
// overflow. hence a few helper functions for size calculations that
// multiply integers together, making sure that they're non-negative
// and no overflow occurs.

// return 1 if the sum is valid, 0 on overflow.
// negative terms are considered invalid.
static int pdi__addsizes_valid(int a, int b)
{
   if (b < 0) return 0;
   // now 0 <= b <= INT_MAX, hence also
   // 0 <= INT_MAX - b <= INTMAX.
   // And "a + b <= INT_MAX" (which might overflow) is the
   // same as a <= INT_MAX - b (no overflow)
   return a <= INT_MAX - b;
}

// returns 1 if the product is valid, 0 on overflow.
// negative factors are considered invalid.
static int pdi__mul2sizes_valid(int a, int b)
{
   if (a < 0 || b < 0) return 0;
   if (b == 0) return 1; // mul-by-0 is always safe
   // portable way to check for no overflows in a*b
   return a <= INT_MAX/b;
}

#if !defined(PDI_NO_JPEG) || !defined(PDI_NO_PNG) || !defined(PDI_NO_TGA) || !defined(PDI_NO_HDR)
// returns 1 if "a*b + add" has no negative terms/factors and doesn't overflow
static int pdi__mad2sizes_valid(int a, int b, int add)
{
   return pdi__mul2sizes_valid(a, b) && pdi__addsizes_valid(a*b, add);
}
#endif

// returns 1 if "a*b*c + add" has no negative terms/factors and doesn't overflow
static int pdi__mad3sizes_valid(int a, int b, int c, int add)
{
   return pdi__mul2sizes_valid(a, b) && pdi__mul2sizes_valid(a*b, c) &&
      pdi__addsizes_valid(a*b*c, add);
}

// returns 1 if "a*b*c*d + add" has no negative terms/factors and doesn't overflow
#if !defined(PDI_NO_LINEAR) || !defined(PDI_NO_HDR) || !defined(PDI_NO_PNM)
static int pdi__mad4sizes_valid(int a, int b, int c, int d, int add)
{
   return pdi__mul2sizes_valid(a, b) && pdi__mul2sizes_valid(a*b, c) &&
      pdi__mul2sizes_valid(a*b*c, d) && pdi__addsizes_valid(a*b*c*d, add);
}
#endif

#if !defined(PDI_NO_JPEG) || !defined(PDI_NO_PNG) || !defined(PDI_NO_TGA) || !defined(PDI_NO_HDR)
// mallocs with size overflow checking
static void *pdi__malloc_mad2(int a, int b, int add)
{
   if (!pdi__mad2sizes_valid(a, b, add)) return NULL;
   return pdi__malloc(a*b + add);
}
#endif

static void *pdi__malloc_mad3(int a, int b, int c, int add)
{
   if (!pdi__mad3sizes_valid(a, b, c, add)) return NULL;
   return pdi__malloc(a*b*c + add);
}

#if !defined(PDI_NO_LINEAR) || !defined(PDI_NO_HDR) || !defined(PDI_NO_PNM)
static void *pdi__malloc_mad4(int a, int b, int c, int d, int add)
{
   if (!pdi__mad4sizes_valid(a, b, c, d, add)) return NULL;
   return pdi__malloc(a*b*c*d + add);
}
#endif

// returns 1 if the sum of two signed ints is valid (between -2^31 and 2^31-1 inclusive), 0 on overflow.
static int pdi__addints_valid(int a, int b)
{
   if ((a >= 0) != (b >= 0)) return 1; // a and b have different signs, so no overflow
   if (a < 0 && b < 0) return a >= INT_MIN - b; // same as a + b >= INT_MIN; INT_MIN - b cannot overflow since b < 0.
   return a <= INT_MAX - b;
}

// returns 1 if the product of two ints fits in a signed short, 0 on overflow.
static int pdi__mul2shorts_valid(int a, int b)
{
   if (b == 0 || b == -1) return 1; // multiplication by 0 is always 0; check for -1 so SHRT_MIN/b doesn't overflow
   if ((a >= 0) == (b >= 0)) return a <= SHRT_MAX/b; // product is positive, so similar to mul2sizes_valid
   if (b < 0) return a <= SHRT_MIN / b; // same as a * b >= SHRT_MIN
   return a >= SHRT_MIN / b;
}

// pdi__err - error
// pdi__errpf - error returning pointer to float
// pdi__errpuc - error returning pointer to unsigned char

#ifdef PDI_NO_FAILURE_STRINGS
   #define pdi__err(x,y)  0
#elif defined(PDI_FAILURE_USERMSG)
   #define pdi__err(x,y)  pdi__err(y)
#else
   #define pdi__err(x,y)  pdi__err(x)
#endif

#define pdi__errpf(x,y)   ((float *)(size_t) (pdi__err(x,y)?NULL:NULL))
#define pdi__errpuc(x,y)  ((unsigned char *)(size_t) (pdi__err(x,y)?NULL:NULL))

PDIDEF void pdi_image_free(void *retval_from_pdi_load)
{
   PDI_FREE(retval_from_pdi_load);
}

#ifndef PDI_NO_LINEAR
static float   *pdi__ldr_to_hdr(pdi_uc *data, int x, int y, int comp);
#endif

#ifndef PDI_NO_HDR
static pdi_uc *pdi__hdr_to_ldr(float   *data, int x, int y, int comp);
#endif

static int pdi__vertically_flip_on_load_global = 0;

PDIDEF void pdi_set_flip_vertically_on_load(int flag_true_if_should_flip)
{
   pdi__vertically_flip_on_load_global = flag_true_if_should_flip;
}

#ifndef PDI_THREAD_LOCAL
#define pdi__vertically_flip_on_load  pdi__vertically_flip_on_load_global
#else
static PDI_THREAD_LOCAL int pdi__vertically_flip_on_load_local, pdi__vertically_flip_on_load_set;

PDIDEF void pdi_set_flip_vertically_on_load_thread(int flag_true_if_should_flip)
{
   pdi__vertically_flip_on_load_local = flag_true_if_should_flip;
   pdi__vertically_flip_on_load_set = 1;
}

#define pdi__vertically_flip_on_load  (pdi__vertically_flip_on_load_set       \
                                         ? pdi__vertically_flip_on_load_local  \
                                         : pdi__vertically_flip_on_load_global)
#endif // PDI_THREAD_LOCAL

static void *pdi__load_main(pdi__context *s, int *x, int *y, int *comp, int req_comp, pdi__result_info *ri, int bpc)
{
   memset(ri, 0, sizeof(*ri)); // make sure it's initialized if we add new fields
   ri->bits_per_channel = 8; // default is 8 so most paths don't have to be changed
   ri->channel_order = PDI_ORDER_RGB; // all current input & output are this, but this is here so we can add BGR order
   ri->num_channels = 0;

   // test the formats with a very explicit header first (at least a FOURCC
   // or distinctive magic number first)
   #ifndef PDI_NO_PNG
   if (pdi__png_test(s))  return pdi__png_load(s,x,y,comp,req_comp, ri);
   #endif
   #ifndef PDI_NO_BMP
   if (pdi__bmp_test(s))  return pdi__bmp_load(s,x,y,comp,req_comp, ri);
   #endif
   #ifndef PDI_NO_GIF
   if (pdi__gif_test(s))  return pdi__gif_load(s,x,y,comp,req_comp, ri);
   #endif
   #ifndef PDI_NO_PSD
   if (pdi__psd_test(s))  return pdi__psd_load(s,x,y,comp,req_comp, ri, bpc);
   #else
   PDI_NOTUSED(bpc);
   #endif
   #ifndef PDI_NO_PIC
   if (pdi__pic_test(s))  return pdi__pic_load(s,x,y,comp,req_comp, ri);
   #endif

   // then the formats that can end up attempting to load with just 1 or 2
   // bytes matching expectations; these are prone to false positives, so
   // try them later
   #ifndef PDI_NO_JPEG
   if (pdi__jpeg_test(s)) return pdi__jpeg_load(s,x,y,comp,req_comp, ri);
   #endif
   #ifndef PDI_NO_PNM
   if (pdi__pnm_test(s))  return pdi__pnm_load(s,x,y,comp,req_comp, ri);
   #endif

   #ifndef PDI_NO_HDR
   if (pdi__hdr_test(s)) {
      float *hdr = pdi__hdr_load(s, x,y,comp,req_comp, ri);
      return pdi__hdr_to_ldr(hdr, *x, *y, req_comp ? req_comp : *comp);
   }
   #endif

   #ifndef PDI_NO_TGA
   // test tga last because it's a crappy test!
   if (pdi__tga_test(s))
      return pdi__tga_load(s,x,y,comp,req_comp, ri);
   #endif

   return pdi__errpuc("unknown image type", "Image not of any known type, or corrupt");
}

static pdi_uc *pdi__convert_16_to_8(pdi__uint16 *orig, int w, int h, int channels)
{
   int i;
   int img_len = w * h * channels;
   pdi_uc *reduced;

   reduced = (pdi_uc *) pdi__malloc(img_len);
   if (reduced == NULL) return pdi__errpuc("outofmem", "Out of memory");

   for (i = 0; i < img_len; ++i)
      reduced[i] = (pdi_uc)((orig[i] >> 8) & 0xFF); // top half of each byte is sufficient approx of 16->8 bit scaling

   PDI_FREE(orig);
   return reduced;
}

static pdi__uint16 *pdi__convert_8_to_16(pdi_uc *orig, int w, int h, int channels)
{
   int i;
   int img_len = w * h * channels;
   pdi__uint16 *enlarged;

   enlarged = (pdi__uint16 *) pdi__malloc(img_len*2);
   if (enlarged == NULL) return (pdi__uint16 *) pdi__errpuc("outofmem", "Out of memory");

   for (i = 0; i < img_len; ++i)
      enlarged[i] = (pdi__uint16)((orig[i] << 8) + orig[i]); // replicate to high and low byte, maps 0->0, 255->0xffff

   PDI_FREE(orig);
   return enlarged;
}

static void pdi__vertical_flip(void *image, int w, int h, int bytes_per_pixel)
{
   int row;
   size_t bytes_per_row = (size_t)w * bytes_per_pixel;
   pdi_uc temp[2048];
   pdi_uc *bytes = (pdi_uc *)image;

   for (row = 0; row < (h>>1); row++) {
      pdi_uc *row0 = bytes + row*bytes_per_row;
      pdi_uc *row1 = bytes + (h - row - 1)*bytes_per_row;
      // swap row0 with row1
      size_t bytes_left = bytes_per_row;
      while (bytes_left) {
         size_t bytes_copy = (bytes_left < sizeof(temp)) ? bytes_left : sizeof(temp);
         memcpy(temp, row0, bytes_copy);
         memcpy(row0, row1, bytes_copy);
         memcpy(row1, temp, bytes_copy);
         row0 += bytes_copy;
         row1 += bytes_copy;
         bytes_left -= bytes_copy;
      }
   }
}

#ifndef PDI_NO_GIF
static void pdi__vertical_flip_slices(void *image, int w, int h, int z, int bytes_per_pixel)
{
   int slice;
   int slice_size = w * h * bytes_per_pixel;

   pdi_uc *bytes = (pdi_uc *)image;
   for (slice = 0; slice < z; ++slice) {
      pdi__vertical_flip(bytes, w, h, bytes_per_pixel);
      bytes += slice_size;
   }
}
#endif

static unsigned char *pdi__load_and_postprocess_8bit(pdi__context *s, int *x, int *y, int *comp, int req_comp)
{
   pdi__result_info ri;
   void *result = pdi__load_main(s, x, y, comp, req_comp, &ri, 8);

   if (result == NULL)
      return NULL;

   // it is the responsibility of the loaders to make sure we get either 8 or 16 bit.
   PDI_ASSERT(ri.bits_per_channel == 8 || ri.bits_per_channel == 16);

   if (ri.bits_per_channel != 8) {
      result = pdi__convert_16_to_8((pdi__uint16 *) result, *x, *y, req_comp == 0 ? *comp : req_comp);
      ri.bits_per_channel = 8;
   }

   // @TODO: move pdi__convert_format to here

   if (pdi__vertically_flip_on_load) {
      int channels = req_comp ? req_comp : *comp;
      pdi__vertical_flip(result, *x, *y, channels * sizeof(pdi_uc));
   }

   return (unsigned char *) result;
}

static pdi__uint16 *pdi__load_and_postprocess_16bit(pdi__context *s, int *x, int *y, int *comp, int req_comp)
{
   pdi__result_info ri;
   void *result = pdi__load_main(s, x, y, comp, req_comp, &ri, 16);

   if (result == NULL)
      return NULL;

   // it is the responsibility of the loaders to make sure we get either 8 or 16 bit.
   PDI_ASSERT(ri.bits_per_channel == 8 || ri.bits_per_channel == 16);

   if (ri.bits_per_channel != 16) {
      result = pdi__convert_8_to_16((pdi_uc *) result, *x, *y, req_comp == 0 ? *comp : req_comp);
      ri.bits_per_channel = 16;
   }

   // @TODO: move pdi__convert_format16 to here
   // @TODO: special case RGB-to-Y (and RGBA-to-YA) for 8-bit-to-16-bit case to keep more precision

   if (pdi__vertically_flip_on_load) {
      int channels = req_comp ? req_comp : *comp;
      pdi__vertical_flip(result, *x, *y, channels * sizeof(pdi__uint16));
   }

   return (pdi__uint16 *) result;
}

#if !defined(PDI_NO_HDR) && !defined(PDI_NO_LINEAR)
static void pdi__float_postprocess(float *result, int *x, int *y, int *comp, int req_comp)
{
   if (pdi__vertically_flip_on_load && result != NULL) {
      int channels = req_comp ? req_comp : *comp;
      pdi__vertical_flip(result, *x, *y, channels * sizeof(float));
   }
}
#endif

#ifndef PDI_NO_STDIO

#if defined(_WIN32) && defined(PDI_WINDOWS_UTF8)
PDI_EXTERN __declspec(dllimport) int __stdcall MultiByteToWideChar(unsigned int cp, unsigned long flags, const char *str, int cbmb, wchar_t *widestr, int cchwide);
PDI_EXTERN __declspec(dllimport) int __stdcall WideCharToMultiByte(unsigned int cp, unsigned long flags, const wchar_t *widestr, int cchwide, char *str, int cbmb, const char *defchar, int *used_default);
#endif

#if defined(_WIN32) && defined(PDI_WINDOWS_UTF8)
PDIDEF int pdi_convert_wchar_to_utf8(char *buffer, size_t bufferlen, const wchar_t* input)
{
	return WideCharToMultiByte(65001 /* UTF8 */, 0, input, -1, buffer, (int) bufferlen, NULL, NULL);
}
#endif

static FILE *pdi__fopen(char const *filename, char const *mode)
{
   FILE *f;
#if defined(_WIN32) && defined(PDI_WINDOWS_UTF8)
   wchar_t wMode[64];
   wchar_t wFilename[1024];
	if (0 == MultiByteToWideChar(65001 /* UTF8 */, 0, filename, -1, wFilename, sizeof(wFilename)/sizeof(*wFilename)))
      return 0;

	if (0 == MultiByteToWideChar(65001 /* UTF8 */, 0, mode, -1, wMode, sizeof(wMode)/sizeof(*wMode)))
      return 0;

#if defined(_MSC_VER) && _MSC_VER >= 1400
	if (0 != _wfopen_s(&f, wFilename, wMode))
		f = 0;
#else
   f = _wfopen(wFilename, wMode);
#endif

#elif defined(_MSC_VER) && _MSC_VER >= 1400
   if (0 != fopen_s(&f, filename, mode))
      f=0;
#else
   f = fopen(filename, mode);
#endif
   return f;
}


PDIDEF pdi_uc *pdi_load(char const *filename, int *x, int *y, int *comp, int req_comp)
{
   FILE *f = pdi__fopen(filename, "rb");
   unsigned char *result;
   if (!f) return pdi__errpuc("can't fopen", "Unable to open file");
   result = pdi_load_from_file(f,x,y,comp,req_comp);
   fclose(f);
   return result;
}

PDIDEF pdi_uc *pdi_load_from_file(FILE *f, int *x, int *y, int *comp, int req_comp)
{
   unsigned char *result;
   pdi__context s;
   pdi__start_file(&s,f);
   result = pdi__load_and_postprocess_8bit(&s,x,y,comp,req_comp);
   if (result) {
      // need to 'unget' all the characters in the IO buffer
      fseek(f, - (int) (s.img_buffer_end - s.img_buffer), SEEK_CUR);
   }
   return result;
}

PDIDEF pdi__uint16 *pdi_load_from_file_16(FILE *f, int *x, int *y, int *comp, int req_comp)
{
   pdi__uint16 *result;
   pdi__context s;
   pdi__start_file(&s,f);
   result = pdi__load_and_postprocess_16bit(&s,x,y,comp,req_comp);
   if (result) {
      // need to 'unget' all the characters in the IO buffer
      fseek(f, - (int) (s.img_buffer_end - s.img_buffer), SEEK_CUR);
   }
   return result;
}

PDIDEF pdi_us *pdi_load_16(char const *filename, int *x, int *y, int *comp, int req_comp)
{
   FILE *f = pdi__fopen(filename, "rb");
   pdi__uint16 *result;
   if (!f) return (pdi_us *) pdi__errpuc("can't fopen", "Unable to open file");
   result = pdi_load_from_file_16(f,x,y,comp,req_comp);
   fclose(f);
   return result;
}


#endif //!PDI_NO_STDIO

PDIDEF pdi_us *pdi_load_16_from_memory(pdi_uc const *buffer, int len, int *x, int *y, int *channels_in_file, int desired_channels)
{
   pdi__context s;
   pdi__start_mem(&s,buffer,len);
   return pdi__load_and_postprocess_16bit(&s,x,y,channels_in_file,desired_channels);
}

PDIDEF pdi_us *pdi_load_16_from_callbacks(pdi_io_callbacks const *clbk, void *user, int *x, int *y, int *channels_in_file, int desired_channels)
{
   pdi__context s;
   pdi__start_callbacks(&s, (pdi_io_callbacks *)clbk, user);
   return pdi__load_and_postprocess_16bit(&s,x,y,channels_in_file,desired_channels);
}

PDIDEF pdi_uc *pdi_load_from_memory(pdi_uc const *buffer, int len, int *x, int *y, int *comp, int req_comp)
{
   pdi__context s;
   pdi__start_mem(&s,buffer,len);
   return pdi__load_and_postprocess_8bit(&s,x,y,comp,req_comp);
}

PDIDEF pdi_uc *pdi_load_from_callbacks(pdi_io_callbacks const *clbk, void *user, int *x, int *y, int *comp, int req_comp)
{
   pdi__context s;
   pdi__start_callbacks(&s, (pdi_io_callbacks *) clbk, user);
   return pdi__load_and_postprocess_8bit(&s,x,y,comp,req_comp);
}

#ifndef PDI_NO_GIF
PDIDEF pdi_uc *pdi_load_gif_from_memory(pdi_uc const *buffer, int len, int **delays, int *x, int *y, int *z, int *comp, int req_comp)
{
   unsigned char *result;
   pdi__context s;
   pdi__start_mem(&s,buffer,len);

   result = (unsigned char*) pdi__load_gif_main(&s, delays, x, y, z, comp, req_comp);
   if (pdi__vertically_flip_on_load) {
      pdi__vertical_flip_slices( result, *x, *y, *z, *comp );
   }

   return result;
}
#endif

#ifndef PDI_NO_LINEAR
static float *pdi__loadf_main(pdi__context *s, int *x, int *y, int *comp, int req_comp)
{
   unsigned char *data;
   #ifndef PDI_NO_HDR
   if (pdi__hdr_test(s)) {
      pdi__result_info ri;
      float *hdr_data = pdi__hdr_load(s,x,y,comp,req_comp, &ri);
      if (hdr_data)
         pdi__float_postprocess(hdr_data,x,y,comp,req_comp);
      return hdr_data;
   }
   #endif
   data = pdi__load_and_postprocess_8bit(s, x, y, comp, req_comp);
   if (data)
      return pdi__ldr_to_hdr(data, *x, *y, req_comp ? req_comp : *comp);
   return pdi__errpf("unknown image type", "Image not of any known type, or corrupt");
}

PDIDEF float *pdi_loadf_from_memory(pdi_uc const *buffer, int len, int *x, int *y, int *comp, int req_comp)
{
   pdi__context s;
   pdi__start_mem(&s,buffer,len);
   return pdi__loadf_main(&s,x,y,comp,req_comp);
}

PDIDEF float *pdi_loadf_from_callbacks(pdi_io_callbacks const *clbk, void *user, int *x, int *y, int *comp, int req_comp)
{
   pdi__context s;
   pdi__start_callbacks(&s, (pdi_io_callbacks *) clbk, user);
   return pdi__loadf_main(&s,x,y,comp,req_comp);
}

#ifndef PDI_NO_STDIO
PDIDEF float *pdi_loadf(char const *filename, int *x, int *y, int *comp, int req_comp)
{
   float *result;
   FILE *f = pdi__fopen(filename, "rb");
   if (!f) return pdi__errpf("can't fopen", "Unable to open file");
   result = pdi_loadf_from_file(f,x,y,comp,req_comp);
   fclose(f);
   return result;
}

PDIDEF float *pdi_loadf_from_file(FILE *f, int *x, int *y, int *comp, int req_comp)
{
   pdi__context s;
   pdi__start_file(&s,f);
   return pdi__loadf_main(&s,x,y,comp,req_comp);
}
#endif // !PDI_NO_STDIO

#endif // !PDI_NO_LINEAR

// these is-hdr-or-not is defined independent of whether PDI_NO_LINEAR is
// defined, for API simplicity; if PDI_NO_LINEAR is defined, it always
// reports false!

PDIDEF int pdi_is_hdr_from_memory(pdi_uc const *buffer, int len)
{
   #ifndef PDI_NO_HDR
   pdi__context s;
   pdi__start_mem(&s,buffer,len);
   return pdi__hdr_test(&s);
   #else
   PDI_NOTUSED(buffer);
   PDI_NOTUSED(len);
   return 0;
   #endif
}

#ifndef PDI_NO_STDIO
PDIDEF int      pdi_is_hdr          (char const *filename)
{
   FILE *f = pdi__fopen(filename, "rb");
   int result=0;
   if (f) {
      result = pdi_is_hdr_from_file(f);
      fclose(f);
   }
   return result;
}

PDIDEF int pdi_is_hdr_from_file(FILE *f)
{
   #ifndef PDI_NO_HDR
   long pos = ftell(f);
   int res;
   pdi__context s;
   pdi__start_file(&s,f);
   res = pdi__hdr_test(&s);
   fseek(f, pos, SEEK_SET);
   return res;
   #else
   PDI_NOTUSED(f);
   return 0;
   #endif
}
#endif // !PDI_NO_STDIO

PDIDEF int      pdi_is_hdr_from_callbacks(pdi_io_callbacks const *clbk, void *user)
{
   #ifndef PDI_NO_HDR
   pdi__context s;
   pdi__start_callbacks(&s, (pdi_io_callbacks *) clbk, user);
   return pdi__hdr_test(&s);
   #else
   PDI_NOTUSED(clbk);
   PDI_NOTUSED(user);
   return 0;
   #endif
}

#ifndef PDI_NO_LINEAR
static float pdi__l2h_gamma=2.2f, pdi__l2h_scale=1.0f;

PDIDEF void   pdi_ldr_to_hdr_gamma(float gamma) { pdi__l2h_gamma = gamma; }
PDIDEF void   pdi_ldr_to_hdr_scale(float scale) { pdi__l2h_scale = scale; }
#endif

static float pdi__h2l_gamma_i=1.0f/2.2f, pdi__h2l_scale_i=1.0f;

PDIDEF void   pdi_hdr_to_ldr_gamma(float gamma) { pdi__h2l_gamma_i = 1/gamma; }
PDIDEF void   pdi_hdr_to_ldr_scale(float scale) { pdi__h2l_scale_i = 1/scale; }


//////////////////////////////////////////////////////////////////////////////
//
// Common code used by all image loaders
//

enum
{
   PDI__SCAN_load=0,
   PDI__SCAN_type,
   PDI__SCAN_header
};

static void pdi__refill_buffer(pdi__context *s)
{
   int n = (s->io.read)(s->io_user_data,(char*)s->buffer_start,s->buflen);
   s->callback_already_read += (int) (s->img_buffer - s->img_buffer_original);
   if (n == 0) {
      // at end of file, treat same as if from memory, but need to handle case
      // where s->img_buffer isn't pointing to safe memory, e.g. 0-byte file
      s->read_from_callbacks = 0;
      s->img_buffer = s->buffer_start;
      s->img_buffer_end = s->buffer_start+1;
      *s->img_buffer = 0;
   } else {
      s->img_buffer = s->buffer_start;
      s->img_buffer_end = s->buffer_start + n;
   }
}

pdi_inline static pdi_uc pdi__get8(pdi__context *s)
{
   if (s->img_buffer < s->img_buffer_end)
      return *s->img_buffer++;
   if (s->read_from_callbacks) {
      pdi__refill_buffer(s);
      return *s->img_buffer++;
   }
   return 0;
}

#if defined(PDI_NO_JPEG) && defined(PDI_NO_HDR) && defined(PDI_NO_PIC) && defined(PDI_NO_PNM)
// nothing
#else
pdi_inline static int pdi__at_eof(pdi__context *s)
{
   if (s->io.read) {
      if (!(s->io.eof)(s->io_user_data)) return 0;
      // if feof() is true, check if buffer = end
      // special case: we've only got the special 0 character at the end
      if (s->read_from_callbacks == 0) return 1;
   }

   return s->img_buffer >= s->img_buffer_end;
}
#endif

#if defined(PDI_NO_JPEG) && defined(PDI_NO_PNG) && defined(PDI_NO_BMP) && defined(PDI_NO_PSD) && defined(PDI_NO_TGA) && defined(PDI_NO_GIF) && defined(PDI_NO_PIC)
// nothing
#else
static void pdi__skip(pdi__context *s, int n)
{
   if (n == 0) return;  // already there!
   if (n < 0) {
      s->img_buffer = s->img_buffer_end;
      return;
   }
   if (s->io.read) {
      int blen = (int) (s->img_buffer_end - s->img_buffer);
      if (blen < n) {
         s->img_buffer = s->img_buffer_end;
         (s->io.skip)(s->io_user_data, n - blen);
         return;
      }
   }
   s->img_buffer += n;
}
#endif

#if defined(PDI_NO_PNG) && defined(PDI_NO_TGA) && defined(PDI_NO_HDR) && defined(PDI_NO_PNM)
// nothing
#else
static int pdi__getn(pdi__context *s, pdi_uc *buffer, int n)
{
   if (s->io.read) {
      int blen = (int) (s->img_buffer_end - s->img_buffer);
      if (blen < n) {
         int res, count;

         memcpy(buffer, s->img_buffer, blen);

         count = (s->io.read)(s->io_user_data, (char*) buffer + blen, n - blen);
         res = (count == (n-blen));
         s->img_buffer = s->img_buffer_end;
         return res;
      }
   }

   if (s->img_buffer+n <= s->img_buffer_end) {
      memcpy(buffer, s->img_buffer, n);
      s->img_buffer += n;
      return 1;
   } else
      return 0;
}
#endif

#if defined(PDI_NO_JPEG) && defined(PDI_NO_PNG) && defined(PDI_NO_PSD) && defined(PDI_NO_PIC)
// nothing
#else
static int pdi__get16be(pdi__context *s)
{
   int z = pdi__get8(s);
   return (z << 8) + pdi__get8(s);
}
#endif

#if defined(PDI_NO_PNG) && defined(PDI_NO_PSD) && defined(PDI_NO_PIC)
// nothing
#else
static pdi__uint32 pdi__get32be(pdi__context *s)
{
   pdi__uint32 z = pdi__get16be(s);
   return (z << 16) + pdi__get16be(s);
}
#endif

#if defined(PDI_NO_BMP) && defined(PDI_NO_TGA) && defined(PDI_NO_GIF)
// nothing
#else
static int pdi__get16le(pdi__context *s)
{
   int z = pdi__get8(s);
   return z + (pdi__get8(s) << 8);
}
#endif

#ifndef PDI_NO_BMP
static pdi__uint32 pdi__get32le(pdi__context *s)
{
   pdi__uint32 z = pdi__get16le(s);
   z += (pdi__uint32)pdi__get16le(s) << 16;
   return z;
}
#endif

#define PDI__BYTECAST(x)  ((pdi_uc) ((x) & 255))  // truncate int to byte without warnings

#if defined(PDI_NO_JPEG) && defined(PDI_NO_PNG) && defined(PDI_NO_BMP) && defined(PDI_NO_PSD) && defined(PDI_NO_TGA) && defined(PDI_NO_GIF) && defined(PDI_NO_PIC) && defined(PDI_NO_PNM)
// nothing
#else
//////////////////////////////////////////////////////////////////////////////
//
//  generic converter from built-in img_n to req_comp
//    individual types do this automatically as much as possible (e.g. jpeg
//    does all cases internally since it needs to colorspace convert anyway,
//    and it never has alpha, so very few cases ). png can automatically
//    interleave an alpha=255 channel, but falls back to this for other cases
//
//  assume data buffer is malloced, so malloc a new one and free that one
//  only failure mode is malloc failing

static pdi_uc pdi__compute_y(int r, int g, int b)
{
   return (pdi_uc) (((r*77) + (g*150) +  (29*b)) >> 8);
}
#endif

#if defined(PDI_NO_PNG) && defined(PDI_NO_BMP) && defined(PDI_NO_PSD) && defined(PDI_NO_TGA) && defined(PDI_NO_GIF) && defined(PDI_NO_PIC) && defined(PDI_NO_PNM)
// nothing
#else
static unsigned char *pdi__convert_format(unsigned char *data, int img_n, int req_comp, unsigned int x, unsigned int y)
{
   int i,j;
   unsigned char *good;

   if (req_comp == img_n) return data;
   PDI_ASSERT(req_comp >= 1 && req_comp <= 4);

   good = (unsigned char *) pdi__malloc_mad3(req_comp, x, y, 0);
   if (good == NULL) {
      PDI_FREE(data);
      return pdi__errpuc("outofmem", "Out of memory");
   }

   for (j=0; j < (int) y; ++j) {
      unsigned char *src  = data + j * x * img_n   ;
      unsigned char *dest = good + j * x * req_comp;

      #define PDI__COMBO(a,b)  ((a)*8+(b))
      #define PDI__CASE(a,b)   case PDI__COMBO(a,b): for(i=x-1; i >= 0; --i, src += a, dest += b)
      // convert source image with img_n components to one with req_comp components;
      // avoid switch per pixel, so use switch per scanline and massive macros
      switch (PDI__COMBO(img_n, req_comp)) {
         PDI__CASE(1,2) { dest[0]=src[0]; dest[1]=255;                                     } break;
         PDI__CASE(1,3) { dest[0]=dest[1]=dest[2]=src[0];                                  } break;
         PDI__CASE(1,4) { dest[0]=dest[1]=dest[2]=src[0]; dest[3]=255;                     } break;
         PDI__CASE(2,1) { dest[0]=src[0];                                                  } break;
         PDI__CASE(2,3) { dest[0]=dest[1]=dest[2]=src[0];                                  } break;
         PDI__CASE(2,4) { dest[0]=dest[1]=dest[2]=src[0]; dest[3]=src[1];                  } break;
         PDI__CASE(3,4) { dest[0]=src[0];dest[1]=src[1];dest[2]=src[2];dest[3]=255;        } break;
         PDI__CASE(3,1) { dest[0]=pdi__compute_y(src[0],src[1],src[2]);                   } break;
         PDI__CASE(3,2) { dest[0]=pdi__compute_y(src[0],src[1],src[2]); dest[1] = 255;    } break;
         PDI__CASE(4,1) { dest[0]=pdi__compute_y(src[0],src[1],src[2]);                   } break;
         PDI__CASE(4,2) { dest[0]=pdi__compute_y(src[0],src[1],src[2]); dest[1] = src[3]; } break;
         PDI__CASE(4,3) { dest[0]=src[0];dest[1]=src[1];dest[2]=src[2];                    } break;
         default: PDI_ASSERT(0); PDI_FREE(data); PDI_FREE(good); return pdi__errpuc("unsupported", "Unsupported format conversion");
      }
      #undef PDI__CASE
   }

   PDI_FREE(data);
   return good;
}
#endif

#if defined(PDI_NO_PNG) && defined(PDI_NO_PSD)
// nothing
#else
static pdi__uint16 pdi__compute_y_16(int r, int g, int b)
{
   return (pdi__uint16) (((r*77) + (g*150) +  (29*b)) >> 8);
}
#endif

#if defined(PDI_NO_PNG) && defined(PDI_NO_PSD)
// nothing
#else
static pdi__uint16 *pdi__convert_format16(pdi__uint16 *data, int img_n, int req_comp, unsigned int x, unsigned int y)
{
   int i,j;
   pdi__uint16 *good;

   if (req_comp == img_n) return data;
   PDI_ASSERT(req_comp >= 1 && req_comp <= 4);

   good = (pdi__uint16 *) pdi__malloc(req_comp * x * y * 2);
   if (good == NULL) {
      PDI_FREE(data);
      return (pdi__uint16 *) pdi__errpuc("outofmem", "Out of memory");
   }

   for (j=0; j < (int) y; ++j) {
      pdi__uint16 *src  = data + j * x * img_n   ;
      pdi__uint16 *dest = good + j * x * req_comp;

      #define PDI__COMBO(a,b)  ((a)*8+(b))
      #define PDI__CASE(a,b)   case PDI__COMBO(a,b): for(i=x-1; i >= 0; --i, src += a, dest += b)
      // convert source image with img_n components to one with req_comp components;
      // avoid switch per pixel, so use switch per scanline and massive macros
      switch (PDI__COMBO(img_n, req_comp)) {
         PDI__CASE(1,2) { dest[0]=src[0]; dest[1]=0xffff;                                     } break;
         PDI__CASE(1,3) { dest[0]=dest[1]=dest[2]=src[0];                                     } break;
         PDI__CASE(1,4) { dest[0]=dest[1]=dest[2]=src[0]; dest[3]=0xffff;                     } break;
         PDI__CASE(2,1) { dest[0]=src[0];                                                     } break;
         PDI__CASE(2,3) { dest[0]=dest[1]=dest[2]=src[0];                                     } break;
         PDI__CASE(2,4) { dest[0]=dest[1]=dest[2]=src[0]; dest[3]=src[1];                     } break;
         PDI__CASE(3,4) { dest[0]=src[0];dest[1]=src[1];dest[2]=src[2];dest[3]=0xffff;        } break;
         PDI__CASE(3,1) { dest[0]=pdi__compute_y_16(src[0],src[1],src[2]);                   } break;
         PDI__CASE(3,2) { dest[0]=pdi__compute_y_16(src[0],src[1],src[2]); dest[1] = 0xffff; } break;
         PDI__CASE(4,1) { dest[0]=pdi__compute_y_16(src[0],src[1],src[2]);                   } break;
         PDI__CASE(4,2) { dest[0]=pdi__compute_y_16(src[0],src[1],src[2]); dest[1] = src[3]; } break;
         PDI__CASE(4,3) { dest[0]=src[0];dest[1]=src[1];dest[2]=src[2];                       } break;
         default: PDI_ASSERT(0); PDI_FREE(data); PDI_FREE(good); return (pdi__uint16*) pdi__errpuc("unsupported", "Unsupported format conversion");
      }
      #undef PDI__CASE
   }

   PDI_FREE(data);
   return good;
}
#endif

#ifndef PDI_NO_LINEAR
static float   *pdi__ldr_to_hdr(pdi_uc *data, int x, int y, int comp)
{
   int i,k,n;
   float *output;
   if (!data) return NULL;
   output = (float *) pdi__malloc_mad4(x, y, comp, sizeof(float), 0);
   if (output == NULL) { PDI_FREE(data); return pdi__errpf("outofmem", "Out of memory"); }
   // compute number of non-alpha components
   if (comp & 1) n = comp; else n = comp-1;
   for (i=0; i < x*y; ++i) {
      for (k=0; k < n; ++k) {
         output[i*comp + k] = (float) (pow(data[i*comp+k]/255.0f, pdi__l2h_gamma) * pdi__l2h_scale);
      }
   }
   if (n < comp) {
      for (i=0; i < x*y; ++i) {
         output[i*comp + n] = data[i*comp + n]/255.0f;
      }
   }
   PDI_FREE(data);
   return output;
}
#endif

#ifndef PDI_NO_HDR
#define pdi__float2int(x)   ((int) (x))
static pdi_uc *pdi__hdr_to_ldr(float   *data, int x, int y, int comp)
{
   int i,k,n;
   pdi_uc *output;
   if (!data) return NULL;
   output = (pdi_uc *) pdi__malloc_mad3(x, y, comp, 0);
   if (output == NULL) { PDI_FREE(data); return pdi__errpuc("outofmem", "Out of memory"); }
   // compute number of non-alpha components
   if (comp & 1) n = comp; else n = comp-1;
   for (i=0; i < x*y; ++i) {
      for (k=0; k < n; ++k) {
         float z = (float) pow(data[i*comp+k]*pdi__h2l_scale_i, pdi__h2l_gamma_i) * 255 + 0.5f;
         if (z < 0) z = 0;
         if (z > 255) z = 255;
         output[i*comp + k] = (pdi_uc) pdi__float2int(z);
      }
      if (k < comp) {
         float z = data[i*comp+k] * 255 + 0.5f;
         if (z < 0) z = 0;
         if (z > 255) z = 255;
         output[i*comp + k] = (pdi_uc) pdi__float2int(z);
      }
   }
   PDI_FREE(data);
   return output;
}
#endif

//////////////////////////////////////////////////////////////////////////////
//
//  "baseline" JPEG/JFIF decoder
//
//    simple implementation
//      - doesn't support delayed output of y-dimension
//      - simple interface (only one output format: 8-bit interleaved RGB)
//      - doesn't try to recover corrupt jpegs
//      - doesn't allow partial loading, loading multiple at once
//      - still fast on x86 (copying globals into locals doesn't help x86)
//      - allocates lots of intermediate memory (full size of all components)
//        - non-interleaved case requires this anyway
//        - allows good upsampling (see next)
//    high-quality
//      - upsampled channels are bilinearly interpolated, even across blocks
//      - quality integer IDCT derived from IJG's 'slow'
//    performance
//      - fast huffman; reasonable integer IDCT
//      - some SIMD kernels for common paths on targets with SSE2/NEON
//      - uses a lot of intermediate memory, could cache poorly

#ifndef PDI_NO_JPEG

// huffman decoding acceleration
#define FAST_BITS   9  // larger handles more cases; smaller stomps less cache

typedef struct
{
   pdi_uc  fast[1 << FAST_BITS];
   // weirdly, repacking this into AoS is a 10% speed loss, instead of a win
   pdi__uint16 code[256];
   pdi_uc  values[256];
   pdi_uc  size[257];
   unsigned int maxcode[18];
   int    delta[17];   // old 'firstsymbol' - old 'firstcode'
} pdi__huffman;

typedef struct
{
   pdi__context *s;
   pdi__huffman huff_dc[4];
   pdi__huffman huff_ac[4];
   pdi__uint16 dequant[4][64];
   pdi__int16 fast_ac[4][1 << FAST_BITS];

// sizes for components, interleaved MCUs
   int img_h_max, img_v_max;
   int img_mcu_x, img_mcu_y;
   int img_mcu_w, img_mcu_h;

// definition of jpeg image component
   struct
   {
      int id;
      int h,v;
      int tq;
      int hd,ha;
      int dc_pred;

      int x,y,w2,h2;
      pdi_uc *data;
      void *raw_data, *raw_coeff;
      pdi_uc *linebuf;
      short   *coeff;   // progressive only
      int      coeff_w, coeff_h; // number of 8x8 coefficient blocks
   } img_comp[4];

   pdi__uint32   code_buffer; // jpeg entropy-coded buffer
   int            code_bits;   // number of valid bits
   unsigned char  marker;      // marker seen while filling entropy buffer
   int            nomore;      // flag if we saw a marker so must stop

   int            progressive;
   int            spec_start;
   int            spec_end;
   int            succ_high;
   int            succ_low;
   int            eob_run;
   int            jfif;
   int            app14_color_transform; // Adobe APP14 tag
   int            rgb;

   int scan_n, order[4];
   int restart_interval, todo;

// kernels
   void (*idct_block_kernel)(pdi_uc *out, int out_stride, short data[64]);
   void (*YCbCr_to_RGB_kernel)(pdi_uc *out, const pdi_uc *y, const pdi_uc *pcb, const pdi_uc *pcr, int count, int step);
   pdi_uc *(*resample_row_hv_2_kernel)(pdi_uc *out, pdi_uc *in_near, pdi_uc *in_far, int w, int hs);
} pdi__jpeg;

static int pdi__build_huffman(pdi__huffman *h, int *count)
{
   int i,j,k=0;
   unsigned int code;
   // build size list for each symbol (from JPEG spec)
   for (i=0; i < 16; ++i) {
      for (j=0; j < count[i]; ++j) {
         h->size[k++] = (pdi_uc) (i+1);
         if(k >= 257) return pdi__err("bad size list","Corrupt JPEG");
      }
   }
   h->size[k] = 0;

   // compute actual symbols (from jpeg spec)
   code = 0;
   k = 0;
   for(j=1; j <= 16; ++j) {
      // compute delta to add to code to compute symbol id
      h->delta[j] = k - code;
      if (h->size[k] == j) {
         while (h->size[k] == j)
            h->code[k++] = (pdi__uint16) (code++);
         if (code-1 >= (1u << j)) return pdi__err("bad code lengths","Corrupt JPEG");
      }
      // compute largest code + 1 for this size, preshifted as needed later
      h->maxcode[j] = code << (16-j);
      code <<= 1;
   }
   h->maxcode[j] = 0xffffffff;

   // build non-spec acceleration table; 255 is flag for not-accelerated
   memset(h->fast, 255, 1 << FAST_BITS);
   for (i=0; i < k; ++i) {
      int s = h->size[i];
      if (s <= FAST_BITS) {
         int c = h->code[i] << (FAST_BITS-s);
         int m = 1 << (FAST_BITS-s);
         for (j=0; j < m; ++j) {
            h->fast[c+j] = (pdi_uc) i;
         }
      }
   }
   return 1;
}

// build a table that decodes both magnitude and value of small ACs in
// one go.
static void pdi__build_fast_ac(pdi__int16 *fast_ac, pdi__huffman *h)
{
   int i;
   for (i=0; i < (1 << FAST_BITS); ++i) {
      pdi_uc fast = h->fast[i];
      fast_ac[i] = 0;
      if (fast < 255) {
         int rs = h->values[fast];
         int run = (rs >> 4) & 15;
         int magbits = rs & 15;
         int len = h->size[fast];

         if (magbits && len + magbits <= FAST_BITS) {
            // magnitude code followed by receive_extend code
            int k = ((i << len) & ((1 << FAST_BITS) - 1)) >> (FAST_BITS - magbits);
            int m = 1 << (magbits - 1);
            if (k < m) k += (~0U << magbits) + 1;
            // if the result is small enough, we can fit it in fast_ac table
            if (k >= -128 && k <= 127)
               fast_ac[i] = (pdi__int16) ((k * 256) + (run * 16) + (len + magbits));
         }
      }
   }
}

static void pdi__grow_buffer_unsafe(pdi__jpeg *j)
{
   do {
      unsigned int b = j->nomore ? 0 : pdi__get8(j->s);
      if (b == 0xff) {
         int c = pdi__get8(j->s);
         while (c == 0xff) c = pdi__get8(j->s); // consume fill bytes
         if (c != 0) {
            j->marker = (unsigned char) c;
            j->nomore = 1;
            return;
         }
      }
      j->code_buffer |= b << (24 - j->code_bits);
      j->code_bits += 8;
   } while (j->code_bits <= 24);
}

// (1 << n) - 1
static const pdi__uint32 pdi__bmask[17]={0,1,3,7,15,31,63,127,255,511,1023,2047,4095,8191,16383,32767,65535};

// decode a jpeg huffman value from the bitstream
pdi_inline static int pdi__jpeg_huff_decode(pdi__jpeg *j, pdi__huffman *h)
{
   unsigned int temp;
   int c,k;

   if (j->code_bits < 16) pdi__grow_buffer_unsafe(j);

   // look at the top FAST_BITS and determine what symbol ID it is,
   // if the code is <= FAST_BITS
   c = (j->code_buffer >> (32 - FAST_BITS)) & ((1 << FAST_BITS)-1);
   k = h->fast[c];
   if (k < 255) {
      int s = h->size[k];
      if (s > j->code_bits)
         return -1;
      j->code_buffer <<= s;
      j->code_bits -= s;
      return h->values[k];
   }

   // naive test is to shift the code_buffer down so k bits are
   // valid, then test against maxcode. To speed this up, we've
   // preshifted maxcode left so that it has (16-k) 0s at the
   // end; in other words, regardless of the number of bits, it
   // wants to be compared against something shifted to have 16;
   // that way we don't need to shift inside the loop.
   temp = j->code_buffer >> 16;
   for (k=FAST_BITS+1 ; ; ++k)
      if (temp < h->maxcode[k])
         break;
   if (k == 17) {
      // error! code not found
      j->code_bits -= 16;
      return -1;
   }

   if (k > j->code_bits)
      return -1;

   // convert the huffman code to the symbol id
   c = ((j->code_buffer >> (32 - k)) & pdi__bmask[k]) + h->delta[k];
   if(c < 0 || c >= 256) // symbol id out of bounds!
       return -1;
   PDI_ASSERT((((j->code_buffer) >> (32 - h->size[c])) & pdi__bmask[h->size[c]]) == h->code[c]);

   // convert the id to a symbol
   j->code_bits -= k;
   j->code_buffer <<= k;
   return h->values[c];
}

// bias[n] = (-1<<n) + 1
static const int pdi__jbias[16] = {0,-1,-3,-7,-15,-31,-63,-127,-255,-511,-1023,-2047,-4095,-8191,-16383,-32767};

// combined JPEG 'receive' and JPEG 'extend', since baseline
// always extends everything it receives.
pdi_inline static int pdi__extend_receive(pdi__jpeg *j, int n)
{
   unsigned int k;
   int sgn;
   if (j->code_bits < n) pdi__grow_buffer_unsafe(j);
   if (j->code_bits < n) return 0; // ran out of bits from stream, return 0s intead of continuing

   sgn = j->code_buffer >> 31; // sign bit always in MSB; 0 if MSB clear (positive), 1 if MSB set (negative)
   k = pdi_lrot(j->code_buffer, n);
   j->code_buffer = k & ~pdi__bmask[n];
   k &= pdi__bmask[n];
   j->code_bits -= n;
   return k + (pdi__jbias[n] & (sgn - 1));
}

// get some unsigned bits
pdi_inline static int pdi__jpeg_get_bits(pdi__jpeg *j, int n)
{
   unsigned int k;
   if (j->code_bits < n) pdi__grow_buffer_unsafe(j);
   if (j->code_bits < n) return 0; // ran out of bits from stream, return 0s intead of continuing
   k = pdi_lrot(j->code_buffer, n);
   j->code_buffer = k & ~pdi__bmask[n];
   k &= pdi__bmask[n];
   j->code_bits -= n;
   return k;
}

pdi_inline static int pdi__jpeg_get_bit(pdi__jpeg *j)
{
   unsigned int k;
   if (j->code_bits < 1) pdi__grow_buffer_unsafe(j);
   if (j->code_bits < 1) return 0; // ran out of bits from stream, return 0s intead of continuing
   k = j->code_buffer;
   j->code_buffer <<= 1;
   --j->code_bits;
   return k & 0x80000000;
}

// given a value that's at position X in the zigzag stream,
// where does it appear in the 8x8 matrix coded as row-major?
static const pdi_uc pdi__jpeg_dezigzag[64+15] =
{
    0,  1,  8, 16,  9,  2,  3, 10,
   17, 24, 32, 25, 18, 11,  4,  5,
   12, 19, 26, 33, 40, 48, 41, 34,
   27, 20, 13,  6,  7, 14, 21, 28,
   35, 42, 49, 56, 57, 50, 43, 36,
   29, 22, 15, 23, 30, 37, 44, 51,
   58, 59, 52, 45, 38, 31, 39, 46,
   53, 60, 61, 54, 47, 55, 62, 63,
   // let corrupt input sample past end
   63, 63, 63, 63, 63, 63, 63, 63,
   63, 63, 63, 63, 63, 63, 63
};

// decode one 64-entry block--
static int pdi__jpeg_decode_block(pdi__jpeg *j, short data[64], pdi__huffman *hdc, pdi__huffman *hac, pdi__int16 *fac, int b, pdi__uint16 *dequant)
{
   int diff,dc,k;
   int t;

   if (j->code_bits < 16) pdi__grow_buffer_unsafe(j);
   t = pdi__jpeg_huff_decode(j, hdc);
   if (t < 0 || t > 15) return pdi__err("bad huffman code","Corrupt JPEG");

   // 0 all the ac values now so we can do it 32-bits at a time
   memset(data,0,64*sizeof(data[0]));

   diff = t ? pdi__extend_receive(j, t) : 0;
   if (!pdi__addints_valid(j->img_comp[b].dc_pred, diff)) return pdi__err("bad delta","Corrupt JPEG");
   dc = j->img_comp[b].dc_pred + diff;
   j->img_comp[b].dc_pred = dc;
   if (!pdi__mul2shorts_valid(dc, dequant[0])) return pdi__err("can't merge dc and ac", "Corrupt JPEG");
   data[0] = (short) (dc * dequant[0]);

   // decode AC components, see JPEG spec
   k = 1;
   do {
      unsigned int zig;
      int c,r,s;
      if (j->code_bits < 16) pdi__grow_buffer_unsafe(j);
      c = (j->code_buffer >> (32 - FAST_BITS)) & ((1 << FAST_BITS)-1);
      r = fac[c];
      if (r) { // fast-AC path
         k += (r >> 4) & 15; // run
         s = r & 15; // combined length
         if (s > j->code_bits) return pdi__err("bad huffman code", "Combined length longer than code bits available");
         j->code_buffer <<= s;
         j->code_bits -= s;
         // decode into unzigzag'd location
         zig = pdi__jpeg_dezigzag[k++];
         data[zig] = (short) ((r >> 8) * dequant[zig]);
      } else {
         int rs = pdi__jpeg_huff_decode(j, hac);
         if (rs < 0) return pdi__err("bad huffman code","Corrupt JPEG");
         s = rs & 15;
         r = rs >> 4;
         if (s == 0) {
            if (rs != 0xf0) break; // end block
            k += 16;
         } else {
            k += r;
            // decode into unzigzag'd location
            zig = pdi__jpeg_dezigzag[k++];
            data[zig] = (short) (pdi__extend_receive(j,s) * dequant[zig]);
         }
      }
   } while (k < 64);
   return 1;
}

static int pdi__jpeg_decode_block_prog_dc(pdi__jpeg *j, short data[64], pdi__huffman *hdc, int b)
{
   int diff,dc;
   int t;
   if (j->spec_end != 0) return pdi__err("can't merge dc and ac", "Corrupt JPEG");

   if (j->code_bits < 16) pdi__grow_buffer_unsafe(j);

   if (j->succ_high == 0) {
      // first scan for DC coefficient, must be first
      memset(data,0,64*sizeof(data[0])); // 0 all the ac values now
      t = pdi__jpeg_huff_decode(j, hdc);
      if (t < 0 || t > 15) return pdi__err("can't merge dc and ac", "Corrupt JPEG");
      diff = t ? pdi__extend_receive(j, t) : 0;

      if (!pdi__addints_valid(j->img_comp[b].dc_pred, diff)) return pdi__err("bad delta", "Corrupt JPEG");
      dc = j->img_comp[b].dc_pred + diff;
      j->img_comp[b].dc_pred = dc;
      if (!pdi__mul2shorts_valid(dc, 1 << j->succ_low)) return pdi__err("can't merge dc and ac", "Corrupt JPEG");
      data[0] = (short) (dc * (1 << j->succ_low));
   } else {
      // refinement scan for DC coefficient
      if (pdi__jpeg_get_bit(j))
         data[0] += (short) (1 << j->succ_low);
   }
   return 1;
}

// @OPTIMIZE: store non-zigzagged during the decode passes,
// and only de-zigzag when dequantizing
static int pdi__jpeg_decode_block_prog_ac(pdi__jpeg *j, short data[64], pdi__huffman *hac, pdi__int16 *fac)
{
   int k;
   if (j->spec_start == 0) return pdi__err("can't merge dc and ac", "Corrupt JPEG");

   if (j->succ_high == 0) {
      int shift = j->succ_low;

      if (j->eob_run) {
         --j->eob_run;
         return 1;
      }

      k = j->spec_start;
      do {
         unsigned int zig;
         int c,r,s;
         if (j->code_bits < 16) pdi__grow_buffer_unsafe(j);
         c = (j->code_buffer >> (32 - FAST_BITS)) & ((1 << FAST_BITS)-1);
         r = fac[c];
         if (r) { // fast-AC path
            k += (r >> 4) & 15; // run
            s = r & 15; // combined length
            if (s > j->code_bits) return pdi__err("bad huffman code", "Combined length longer than code bits available");
            j->code_buffer <<= s;
            j->code_bits -= s;
            zig = pdi__jpeg_dezigzag[k++];
            data[zig] = (short) ((r >> 8) * (1 << shift));
         } else {
            int rs = pdi__jpeg_huff_decode(j, hac);
            if (rs < 0) return pdi__err("bad huffman code","Corrupt JPEG");
            s = rs & 15;
            r = rs >> 4;
            if (s == 0) {
               if (r < 15) {
                  j->eob_run = (1 << r);
                  if (r)
                     j->eob_run += pdi__jpeg_get_bits(j, r);
                  --j->eob_run;
                  break;
               }
               k += 16;
            } else {
               k += r;
               zig = pdi__jpeg_dezigzag[k++];
               data[zig] = (short) (pdi__extend_receive(j,s) * (1 << shift));
            }
         }
      } while (k <= j->spec_end);
   } else {
      // refinement scan for these AC coefficients

      short bit = (short) (1 << j->succ_low);

      if (j->eob_run) {
         --j->eob_run;
         for (k = j->spec_start; k <= j->spec_end; ++k) {
            short *p = &data[pdi__jpeg_dezigzag[k]];
            if (*p != 0)
               if (pdi__jpeg_get_bit(j))
                  if ((*p & bit)==0) {
                     if (*p > 0)
                        *p += bit;
                     else
                        *p -= bit;
                  }
         }
      } else {
         k = j->spec_start;
         do {
            int r,s;
            int rs = pdi__jpeg_huff_decode(j, hac); // @OPTIMIZE see if we can use the fast path here, advance-by-r is so slow, eh
            if (rs < 0) return pdi__err("bad huffman code","Corrupt JPEG");
            s = rs & 15;
            r = rs >> 4;
            if (s == 0) {
               if (r < 15) {
                  j->eob_run = (1 << r) - 1;
                  if (r)
                     j->eob_run += pdi__jpeg_get_bits(j, r);
                  r = 64; // force end of block
               } else {
                  // r=15 s=0 should write 16 0s, so we just do
                  // a run of 15 0s and then write s (which is 0),
                  // so we don't have to do anything special here
               }
            } else {
               if (s != 1) return pdi__err("bad huffman code", "Corrupt JPEG");
               // sign bit
               if (pdi__jpeg_get_bit(j))
                  s = bit;
               else
                  s = -bit;
            }

            // advance by r
            while (k <= j->spec_end) {
               short *p = &data[pdi__jpeg_dezigzag[k++]];
               if (*p != 0) {
                  if (pdi__jpeg_get_bit(j))
                     if ((*p & bit)==0) {
                        if (*p > 0)
                           *p += bit;
                        else
                           *p -= bit;
                     }
               } else {
                  if (r == 0) {
                     *p = (short) s;
                     break;
                  }
                  --r;
               }
            }
         } while (k <= j->spec_end);
      }
   }
   return 1;
}

// take a -128..127 value and pdi__clamp it and convert to 0..255
pdi_inline static pdi_uc pdi__clamp(int x)
{
   // trick to use a single test to catch both cases
   if ((unsigned int) x > 255) {
      if (x < 0) return 0;
      if (x > 255) return 255;
   }
   return (pdi_uc) x;
}

#define pdi__f2f(x)  ((int) (((x) * 4096 + 0.5)))
#define pdi__fsh(x)  ((x) * 4096)

// derived from jidctint -- DCT_ISLOW
#define PDI__IDCT_1D(s0,s1,s2,s3,s4,s5,s6,s7) \
   int t0,t1,t2,t3,p1,p2,p3,p4,p5,x0,x1,x2,x3; \
   p2 = s2;                                    \
   p3 = s6;                                    \
   p1 = (p2+p3) * pdi__f2f(0.5411961f);       \
   t2 = p1 + p3*pdi__f2f(-1.847759065f);      \
   t3 = p1 + p2*pdi__f2f( 0.765366865f);      \
   p2 = s0;                                    \
   p3 = s4;                                    \
   t0 = pdi__fsh(p2+p3);                      \
   t1 = pdi__fsh(p2-p3);                      \
   x0 = t0+t3;                                 \
   x3 = t0-t3;                                 \
   x1 = t1+t2;                                 \
   x2 = t1-t2;                                 \
   t0 = s7;                                    \
   t1 = s5;                                    \
   t2 = s3;                                    \
   t3 = s1;                                    \
   p3 = t0+t2;                                 \
   p4 = t1+t3;                                 \
   p1 = t0+t3;                                 \
   p2 = t1+t2;                                 \
   p5 = (p3+p4)*pdi__f2f( 1.175875602f);      \
   t0 = t0*pdi__f2f( 0.298631336f);           \
   t1 = t1*pdi__f2f( 2.053119869f);           \
   t2 = t2*pdi__f2f( 3.072711026f);           \
   t3 = t3*pdi__f2f( 1.501321110f);           \
   p1 = p5 + p1*pdi__f2f(-0.899976223f);      \
   p2 = p5 + p2*pdi__f2f(-2.562915447f);      \
   p3 = p3*pdi__f2f(-1.961570560f);           \
   p4 = p4*pdi__f2f(-0.390180644f);           \
   t3 += p1+p4;                                \
   t2 += p2+p3;                                \
   t1 += p2+p4;                                \
   t0 += p1+p3;

static void pdi__idct_block(pdi_uc *out, int out_stride, short data[64])
{
   int i,val[64],*v=val;
   pdi_uc *o;
   short *d = data;

   // columns
   for (i=0; i < 8; ++i,++d, ++v) {
      // if all zeroes, shortcut -- this avoids dequantizing 0s and IDCTing
      if (d[ 8]==0 && d[16]==0 && d[24]==0 && d[32]==0
           && d[40]==0 && d[48]==0 && d[56]==0) {
         //    no shortcut                 0     seconds
         //    (1|2|3|4|5|6|7)==0          0     seconds
         //    all separate               -0.047 seconds
         //    1 && 2|3 && 4|5 && 6|7:    -0.047 seconds
         int dcterm = d[0]*4;
         v[0] = v[8] = v[16] = v[24] = v[32] = v[40] = v[48] = v[56] = dcterm;
      } else {
         PDI__IDCT_1D(d[ 0],d[ 8],d[16],d[24],d[32],d[40],d[48],d[56])
         // constants scaled things up by 1<<12; let's bring them back
         // down, but keep 2 extra bits of precision
         x0 += 512; x1 += 512; x2 += 512; x3 += 512;
         v[ 0] = (x0+t3) >> 10;
         v[56] = (x0-t3) >> 10;
         v[ 8] = (x1+t2) >> 10;
         v[48] = (x1-t2) >> 10;
         v[16] = (x2+t1) >> 10;
         v[40] = (x2-t1) >> 10;
         v[24] = (x3+t0) >> 10;
         v[32] = (x3-t0) >> 10;
      }
   }

   for (i=0, v=val, o=out; i < 8; ++i,v+=8,o+=out_stride) {
      // no fast case since the first 1D IDCT spread components out
      PDI__IDCT_1D(v[0],v[1],v[2],v[3],v[4],v[5],v[6],v[7])
      // constants scaled things up by 1<<12, plus we had 1<<2 from first
      // loop, plus horizontal and vertical each scale by sqrt(8) so together
      // we've got an extra 1<<3, so 1<<17 total we need to remove.
      // so we want to round that, which means adding 0.5 * 1<<17,
      // aka 65536. Also, we'll end up with -128 to 127 that we want
      // to encode as 0..255 by adding 128, so we'll add that before the shift
      x0 += 65536 + (128<<17);
      x1 += 65536 + (128<<17);
      x2 += 65536 + (128<<17);
      x3 += 65536 + (128<<17);
      // tried computing the shifts into temps, or'ing the temps to see
      // if any were out of range, but that was slower
      o[0] = pdi__clamp((x0+t3) >> 17);
      o[7] = pdi__clamp((x0-t3) >> 17);
      o[1] = pdi__clamp((x1+t2) >> 17);
      o[6] = pdi__clamp((x1-t2) >> 17);
      o[2] = pdi__clamp((x2+t1) >> 17);
      o[5] = pdi__clamp((x2-t1) >> 17);
      o[3] = pdi__clamp((x3+t0) >> 17);
      o[4] = pdi__clamp((x3-t0) >> 17);
   }
}

#ifdef PDI_SSE2
// sse2 integer IDCT. not the fastest possible implementation but it
// produces bit-identical results to the generic C version so it's
// fully "transparent".
static void pdi__idct_simd(pdi_uc *out, int out_stride, short data[64])
{
   // This is constructed to match our regular (generic) integer IDCT exactly.
   __m128i row0, row1, row2, row3, row4, row5, row6, row7;
   __m128i tmp;

   // dot product constant: even elems=x, odd elems=y
   #define dct_const(x,y)  _mm_setr_epi16((x),(y),(x),(y),(x),(y),(x),(y))

   // out(0) = c0[even]*x + c0[odd]*y   (c0, x, y 16-bit, out 32-bit)
   // out(1) = c1[even]*x + c1[odd]*y
   #define dct_rot(out0,out1, x,y,c0,c1) \
      __m128i c0##lo = _mm_unpacklo_epi16((x),(y)); \
      __m128i c0##hi = _mm_unpackhi_epi16((x),(y)); \
      __m128i out0##_l = _mm_madd_epi16(c0##lo, c0); \
      __m128i out0##_h = _mm_madd_epi16(c0##hi, c0); \
      __m128i out1##_l = _mm_madd_epi16(c0##lo, c1); \
      __m128i out1##_h = _mm_madd_epi16(c0##hi, c1)

   // out = in << 12  (in 16-bit, out 32-bit)
   #define dct_widen(out, in) \
      __m128i out##_l = _mm_srai_epi32(_mm_unpacklo_epi16(_mm_setzero_si128(), (in)), 4); \
      __m128i out##_h = _mm_srai_epi32(_mm_unpackhi_epi16(_mm_setzero_si128(), (in)), 4)

   // wide add
   #define dct_wadd(out, a, b) \
      __m128i out##_l = _mm_add_epi32(a##_l, b##_l); \
      __m128i out##_h = _mm_add_epi32(a##_h, b##_h)

   // wide sub
   #define dct_wsub(out, a, b) \
      __m128i out##_l = _mm_sub_epi32(a##_l, b##_l); \
      __m128i out##_h = _mm_sub_epi32(a##_h, b##_h)

   // butterfly a/b, add bias, then shift by "s" and pack
   #define dct_bfly32o(out0, out1, a,b,bias,s) \
      { \
         __m128i abiased_l = _mm_add_epi32(a##_l, bias); \
         __m128i abiased_h = _mm_add_epi32(a##_h, bias); \
         dct_wadd(sum, abiased, b); \
         dct_wsub(dif, abiased, b); \
         out0 = _mm_packs_epi32(_mm_srai_epi32(sum_l, s), _mm_srai_epi32(sum_h, s)); \
         out1 = _mm_packs_epi32(_mm_srai_epi32(dif_l, s), _mm_srai_epi32(dif_h, s)); \
      }

   // 8-bit interleave step (for transposes)
   #define dct_interleave8(a, b) \
      tmp = a; \
      a = _mm_unpacklo_epi8(a, b); \
      b = _mm_unpackhi_epi8(tmp, b)

   // 16-bit interleave step (for transposes)
   #define dct_interleave16(a, b) \
      tmp = a; \
      a = _mm_unpacklo_epi16(a, b); \
      b = _mm_unpackhi_epi16(tmp, b)

   #define dct_pass(bias,shift) \
      { \
         /* even part */ \
         dct_rot(t2e,t3e, row2,row6, rot0_0,rot0_1); \
         __m128i sum04 = _mm_add_epi16(row0, row4); \
         __m128i dif04 = _mm_sub_epi16(row0, row4); \
         dct_widen(t0e, sum04); \
         dct_widen(t1e, dif04); \
         dct_wadd(x0, t0e, t3e); \
         dct_wsub(x3, t0e, t3e); \
         dct_wadd(x1, t1e, t2e); \
         dct_wsub(x2, t1e, t2e); \
         /* odd part */ \
         dct_rot(y0o,y2o, row7,row3, rot2_0,rot2_1); \
         dct_rot(y1o,y3o, row5,row1, rot3_0,rot3_1); \
         __m128i sum17 = _mm_add_epi16(row1, row7); \
         __m128i sum35 = _mm_add_epi16(row3, row5); \
         dct_rot(y4o,y5o, sum17,sum35, rot1_0,rot1_1); \
         dct_wadd(x4, y0o, y4o); \
         dct_wadd(x5, y1o, y5o); \
         dct_wadd(x6, y2o, y5o); \
         dct_wadd(x7, y3o, y4o); \
         dct_bfly32o(row0,row7, x0,x7,bias,shift); \
         dct_bfly32o(row1,row6, x1,x6,bias,shift); \
         dct_bfly32o(row2,row5, x2,x5,bias,shift); \
         dct_bfly32o(row3,row4, x3,x4,bias,shift); \
      }

   __m128i rot0_0 = dct_const(pdi__f2f(0.5411961f), pdi__f2f(0.5411961f) + pdi__f2f(-1.847759065f));
   __m128i rot0_1 = dct_const(pdi__f2f(0.5411961f) + pdi__f2f( 0.765366865f), pdi__f2f(0.5411961f));
   __m128i rot1_0 = dct_const(pdi__f2f(1.175875602f) + pdi__f2f(-0.899976223f), pdi__f2f(1.175875602f));
   __m128i rot1_1 = dct_const(pdi__f2f(1.175875602f), pdi__f2f(1.175875602f) + pdi__f2f(-2.562915447f));
   __m128i rot2_0 = dct_const(pdi__f2f(-1.961570560f) + pdi__f2f( 0.298631336f), pdi__f2f(-1.961570560f));
   __m128i rot2_1 = dct_const(pdi__f2f(-1.961570560f), pdi__f2f(-1.961570560f) + pdi__f2f( 3.072711026f));
   __m128i rot3_0 = dct_const(pdi__f2f(-0.390180644f) + pdi__f2f( 2.053119869f), pdi__f2f(-0.390180644f));
   __m128i rot3_1 = dct_const(pdi__f2f(-0.390180644f), pdi__f2f(-0.390180644f) + pdi__f2f( 1.501321110f));

   // rounding biases in column/row passes, see pdi__idct_block for explanation.
   __m128i bias_0 = _mm_set1_epi32(512);
   __m128i bias_1 = _mm_set1_epi32(65536 + (128<<17));

   // load
   row0 = _mm_load_si128((const __m128i *) (data + 0*8));
   row1 = _mm_load_si128((const __m128i *) (data + 1*8));
   row2 = _mm_load_si128((const __m128i *) (data + 2*8));
   row3 = _mm_load_si128((const __m128i *) (data + 3*8));
   row4 = _mm_load_si128((const __m128i *) (data + 4*8));
   row5 = _mm_load_si128((const __m128i *) (data + 5*8));
   row6 = _mm_load_si128((const __m128i *) (data + 6*8));
   row7 = _mm_load_si128((const __m128i *) (data + 7*8));

   // column pass
   dct_pass(bias_0, 10);

   {
      // 16bit 8x8 transpose pass 1
      dct_interleave16(row0, row4);
      dct_interleave16(row1, row5);
      dct_interleave16(row2, row6);
      dct_interleave16(row3, row7);

      // transpose pass 2
      dct_interleave16(row0, row2);
      dct_interleave16(row1, row3);
      dct_interleave16(row4, row6);
      dct_interleave16(row5, row7);

      // transpose pass 3
      dct_interleave16(row0, row1);
      dct_interleave16(row2, row3);
      dct_interleave16(row4, row5);
      dct_interleave16(row6, row7);
   }

   // row pass
   dct_pass(bias_1, 17);

   {
      // pack
      __m128i p0 = _mm_packus_epi16(row0, row1); // a0a1a2a3...a7b0b1b2b3...b7
      __m128i p1 = _mm_packus_epi16(row2, row3);
      __m128i p2 = _mm_packus_epi16(row4, row5);
      __m128i p3 = _mm_packus_epi16(row6, row7);

      // 8bit 8x8 transpose pass 1
      dct_interleave8(p0, p2); // a0e0a1e1...
      dct_interleave8(p1, p3); // c0g0c1g1...

      // transpose pass 2
      dct_interleave8(p0, p1); // a0c0e0g0...
      dct_interleave8(p2, p3); // b0d0f0h0...

      // transpose pass 3
      dct_interleave8(p0, p2); // a0b0c0d0...
      dct_interleave8(p1, p3); // a4b4c4d4...

      // store
      _mm_storel_epi64((__m128i *) out, p0); out += out_stride;
      _mm_storel_epi64((__m128i *) out, _mm_shuffle_epi32(p0, 0x4e)); out += out_stride;
      _mm_storel_epi64((__m128i *) out, p2); out += out_stride;
      _mm_storel_epi64((__m128i *) out, _mm_shuffle_epi32(p2, 0x4e)); out += out_stride;
      _mm_storel_epi64((__m128i *) out, p1); out += out_stride;
      _mm_storel_epi64((__m128i *) out, _mm_shuffle_epi32(p1, 0x4e)); out += out_stride;
      _mm_storel_epi64((__m128i *) out, p3); out += out_stride;
      _mm_storel_epi64((__m128i *) out, _mm_shuffle_epi32(p3, 0x4e));
   }

#undef dct_const
#undef dct_rot
#undef dct_widen
#undef dct_wadd
#undef dct_wsub
#undef dct_bfly32o
#undef dct_interleave8
#undef dct_interleave16
#undef dct_pass
}

#endif // PDI_SSE2

#ifdef PDI_NEON

// NEON integer IDCT. should produce bit-identical
// results to the generic C version.
static void pdi__idct_simd(pdi_uc *out, int out_stride, short data[64])
{
   int16x8_t row0, row1, row2, row3, row4, row5, row6, row7;

   int16x4_t rot0_0 = vdup_n_s16(pdi__f2f(0.5411961f));
   int16x4_t rot0_1 = vdup_n_s16(pdi__f2f(-1.847759065f));
   int16x4_t rot0_2 = vdup_n_s16(pdi__f2f( 0.765366865f));
   int16x4_t rot1_0 = vdup_n_s16(pdi__f2f( 1.175875602f));
   int16x4_t rot1_1 = vdup_n_s16(pdi__f2f(-0.899976223f));
   int16x4_t rot1_2 = vdup_n_s16(pdi__f2f(-2.562915447f));
   int16x4_t rot2_0 = vdup_n_s16(pdi__f2f(-1.961570560f));
   int16x4_t rot2_1 = vdup_n_s16(pdi__f2f(-0.390180644f));
   int16x4_t rot3_0 = vdup_n_s16(pdi__f2f( 0.298631336f));
   int16x4_t rot3_1 = vdup_n_s16(pdi__f2f( 2.053119869f));
   int16x4_t rot3_2 = vdup_n_s16(pdi__f2f( 3.072711026f));
   int16x4_t rot3_3 = vdup_n_s16(pdi__f2f( 1.501321110f));

#define dct_long_mul(out, inq, coeff) \
   int32x4_t out##_l = vmull_s16(vget_low_s16(inq), coeff); \
   int32x4_t out##_h = vmull_s16(vget_high_s16(inq), coeff)

#define dct_long_mac(out, acc, inq, coeff) \
   int32x4_t out##_l = vmlal_s16(acc##_l, vget_low_s16(inq), coeff); \
   int32x4_t out##_h = vmlal_s16(acc##_h, vget_high_s16(inq), coeff)

#define dct_widen(out, inq) \
   int32x4_t out##_l = vshll_n_s16(vget_low_s16(inq), 12); \
   int32x4_t out##_h = vshll_n_s16(vget_high_s16(inq), 12)

// wide add
#define dct_wadd(out, a, b) \
   int32x4_t out##_l = vaddq_s32(a##_l, b##_l); \
   int32x4_t out##_h = vaddq_s32(a##_h, b##_h)

// wide sub
#define dct_wsub(out, a, b) \
   int32x4_t out##_l = vsubq_s32(a##_l, b##_l); \
   int32x4_t out##_h = vsubq_s32(a##_h, b##_h)

// butterfly a/b, then shift using "shiftop" by "s" and pack
#define dct_bfly32o(out0,out1, a,b,shiftop,s) \
   { \
      dct_wadd(sum, a, b); \
      dct_wsub(dif, a, b); \
      out0 = vcombine_s16(shiftop(sum_l, s), shiftop(sum_h, s)); \
      out1 = vcombine_s16(shiftop(dif_l, s), shiftop(dif_h, s)); \
   }

#define dct_pass(shiftop, shift) \
   { \
      /* even part */ \
      int16x8_t sum26 = vaddq_s16(row2, row6); \
      dct_long_mul(p1e, sum26, rot0_0); \
      dct_long_mac(t2e, p1e, row6, rot0_1); \
      dct_long_mac(t3e, p1e, row2, rot0_2); \
      int16x8_t sum04 = vaddq_s16(row0, row4); \
      int16x8_t dif04 = vsubq_s16(row0, row4); \
      dct_widen(t0e, sum04); \
      dct_widen(t1e, dif04); \
      dct_wadd(x0, t0e, t3e); \
      dct_wsub(x3, t0e, t3e); \
      dct_wadd(x1, t1e, t2e); \
      dct_wsub(x2, t1e, t2e); \
      /* odd part */ \
      int16x8_t sum15 = vaddq_s16(row1, row5); \
      int16x8_t sum17 = vaddq_s16(row1, row7); \
      int16x8_t sum35 = vaddq_s16(row3, row5); \
      int16x8_t sum37 = vaddq_s16(row3, row7); \
      int16x8_t sumodd = vaddq_s16(sum17, sum35); \
      dct_long_mul(p5o, sumodd, rot1_0); \
      dct_long_mac(p1o, p5o, sum17, rot1_1); \
      dct_long_mac(p2o, p5o, sum35, rot1_2); \
      dct_long_mul(p3o, sum37, rot2_0); \
      dct_long_mul(p4o, sum15, rot2_1); \
      dct_wadd(sump13o, p1o, p3o); \
      dct_wadd(sump24o, p2o, p4o); \
      dct_wadd(sump23o, p2o, p3o); \
      dct_wadd(sump14o, p1o, p4o); \
      dct_long_mac(x4, sump13o, row7, rot3_0); \
      dct_long_mac(x5, sump24o, row5, rot3_1); \
      dct_long_mac(x6, sump23o, row3, rot3_2); \
      dct_long_mac(x7, sump14o, row1, rot3_3); \
      dct_bfly32o(row0,row7, x0,x7,shiftop,shift); \
      dct_bfly32o(row1,row6, x1,x6,shiftop,shift); \
      dct_bfly32o(row2,row5, x2,x5,shiftop,shift); \
      dct_bfly32o(row3,row4, x3,x4,shiftop,shift); \
   }

   // load
   row0 = vld1q_s16(data + 0*8);
   row1 = vld1q_s16(data + 1*8);
   row2 = vld1q_s16(data + 2*8);
   row3 = vld1q_s16(data + 3*8);
   row4 = vld1q_s16(data + 4*8);
   row5 = vld1q_s16(data + 5*8);
   row6 = vld1q_s16(data + 6*8);
   row7 = vld1q_s16(data + 7*8);

   // add DC bias
   row0 = vaddq_s16(row0, vsetq_lane_s16(1024, vdupq_n_s16(0), 0));

   // column pass
   dct_pass(vrshrn_n_s32, 10);

   // 16bit 8x8 transpose
   {
// these three map to a single VTRN.16, VTRN.32, and VSWP, respectively.
// whether compilers actually get this is another story, sadly.
#define dct_trn16(x, y) { int16x8x2_t t = vtrnq_s16(x, y); x = t.val[0]; y = t.val[1]; }
#define dct_trn32(x, y) { int32x4x2_t t = vtrnq_s32(vreinterpretq_s32_s16(x), vreinterpretq_s32_s16(y)); x = vreinterpretq_s16_s32(t.val[0]); y = vreinterpretq_s16_s32(t.val[1]); }
#define dct_trn64(x, y) { int16x8_t x0 = x; int16x8_t y0 = y; x = vcombine_s16(vget_low_s16(x0), vget_low_s16(y0)); y = vcombine_s16(vget_high_s16(x0), vget_high_s16(y0)); }

      // pass 1
      dct_trn16(row0, row1); // a0b0a2b2a4b4a6b6
      dct_trn16(row2, row3);
      dct_trn16(row4, row5);
      dct_trn16(row6, row7);

      // pass 2
      dct_trn32(row0, row2); // a0b0c0d0a4b4c4d4
      dct_trn32(row1, row3);
      dct_trn32(row4, row6);
      dct_trn32(row5, row7);

      // pass 3
      dct_trn64(row0, row4); // a0b0c0d0e0f0g0h0
      dct_trn64(row1, row5);
      dct_trn64(row2, row6);
      dct_trn64(row3, row7);

#undef dct_trn16
#undef dct_trn32
#undef dct_trn64
   }

   // row pass
   // vrshrn_n_s32 only supports shifts up to 16, we need
   // 17. so do a non-rounding shift of 16 first then follow
   // up with a rounding shift by 1.
   dct_pass(vshrn_n_s32, 16);

   {
      // pack and round
      uint8x8_t p0 = vqrshrun_n_s16(row0, 1);
      uint8x8_t p1 = vqrshrun_n_s16(row1, 1);
      uint8x8_t p2 = vqrshrun_n_s16(row2, 1);
      uint8x8_t p3 = vqrshrun_n_s16(row3, 1);
      uint8x8_t p4 = vqrshrun_n_s16(row4, 1);
      uint8x8_t p5 = vqrshrun_n_s16(row5, 1);
      uint8x8_t p6 = vqrshrun_n_s16(row6, 1);
      uint8x8_t p7 = vqrshrun_n_s16(row7, 1);

      // again, these can translate into one instruction, but often don't.
#define dct_trn8_8(x, y) { uint8x8x2_t t = vtrn_u8(x, y); x = t.val[0]; y = t.val[1]; }
#define dct_trn8_16(x, y) { uint16x4x2_t t = vtrn_u16(vreinterpret_u16_u8(x), vreinterpret_u16_u8(y)); x = vreinterpret_u8_u16(t.val[0]); y = vreinterpret_u8_u16(t.val[1]); }
#define dct_trn8_32(x, y) { uint32x2x2_t t = vtrn_u32(vreinterpret_u32_u8(x), vreinterpret_u32_u8(y)); x = vreinterpret_u8_u32(t.val[0]); y = vreinterpret_u8_u32(t.val[1]); }

      // sadly can't use interleaved stores here since we only write
      // 8 bytes to each scan line!

      // 8x8 8-bit transpose pass 1
      dct_trn8_8(p0, p1);
      dct_trn8_8(p2, p3);
      dct_trn8_8(p4, p5);
      dct_trn8_8(p6, p7);

      // pass 2
      dct_trn8_16(p0, p2);
      dct_trn8_16(p1, p3);
      dct_trn8_16(p4, p6);
      dct_trn8_16(p5, p7);

      // pass 3
      dct_trn8_32(p0, p4);
      dct_trn8_32(p1, p5);
      dct_trn8_32(p2, p6);
      dct_trn8_32(p3, p7);

      // store
      vst1_u8(out, p0); out += out_stride;
      vst1_u8(out, p1); out += out_stride;
      vst1_u8(out, p2); out += out_stride;
      vst1_u8(out, p3); out += out_stride;
      vst1_u8(out, p4); out += out_stride;
      vst1_u8(out, p5); out += out_stride;
      vst1_u8(out, p6); out += out_stride;
      vst1_u8(out, p7);

#undef dct_trn8_8
#undef dct_trn8_16
#undef dct_trn8_32
   }

#undef dct_long_mul
#undef dct_long_mac
#undef dct_widen
#undef dct_wadd
#undef dct_wsub
#undef dct_bfly32o
#undef dct_pass
}

#endif // PDI_NEON

#define PDI__MARKER_none  0xff
// if there's a pending marker from the entropy stream, return that
// otherwise, fetch from the stream and get a marker. if there's no
// marker, return 0xff, which is never a valid marker value
static pdi_uc pdi__get_marker(pdi__jpeg *j)
{
   pdi_uc x;
   if (j->marker != PDI__MARKER_none) { x = j->marker; j->marker = PDI__MARKER_none; return x; }
   x = pdi__get8(j->s);
   if (x != 0xff) return PDI__MARKER_none;
   while (x == 0xff)
      x = pdi__get8(j->s); // consume repeated 0xff fill bytes
   return x;
}

// in each scan, we'll have scan_n components, and the order
// of the components is specified by order[]
#define PDI__RESTART(x)     ((x) >= 0xd0 && (x) <= 0xd7)

// after a restart interval, pdi__jpeg_reset the entropy decoder and
// the dc prediction
static void pdi__jpeg_reset(pdi__jpeg *j)
{
   j->code_bits = 0;
   j->code_buffer = 0;
   j->nomore = 0;
   j->img_comp[0].dc_pred = j->img_comp[1].dc_pred = j->img_comp[2].dc_pred = j->img_comp[3].dc_pred = 0;
   j->marker = PDI__MARKER_none;
   j->todo = j->restart_interval ? j->restart_interval : 0x7fffffff;
   j->eob_run = 0;
   // no more than 1<<31 MCUs if no restart_interal? that's plenty safe,
   // since we don't even allow 1<<30 pixels
}

static int pdi__parse_entropy_coded_data(pdi__jpeg *z)
{
   pdi__jpeg_reset(z);
   if (!z->progressive) {
      if (z->scan_n == 1) {
         int i,j;
         PDI_SIMD_ALIGN(short, data[64]);
         int n = z->order[0];
         // non-interleaved data, we just need to process one block at a time,
         // in trivial scanline order
         // number of blocks to do just depends on how many actual "pixels" this
         // component has, independent of interleaved MCU blocking and such
         int w = (z->img_comp[n].x+7) >> 3;
         int h = (z->img_comp[n].y+7) >> 3;
         for (j=0; j < h; ++j) {
            for (i=0; i < w; ++i) {
               int ha = z->img_comp[n].ha;
               if (!pdi__jpeg_decode_block(z, data, z->huff_dc+z->img_comp[n].hd, z->huff_ac+ha, z->fast_ac[ha], n, z->dequant[z->img_comp[n].tq])) return 0;
               z->idct_block_kernel(z->img_comp[n].data+z->img_comp[n].w2*j*8+i*8, z->img_comp[n].w2, data);
               // every data block is an MCU, so countdown the restart interval
               if (--z->todo <= 0) {
                  if (z->code_bits < 24) pdi__grow_buffer_unsafe(z);
                  // if it's NOT a restart, then just bail, so we get corrupt data
                  // rather than no data
                  if (!PDI__RESTART(z->marker)) return 1;
                  pdi__jpeg_reset(z);
               }
            }
         }
         return 1;
      } else { // interleaved
         int i,j,k,x,y;
         PDI_SIMD_ALIGN(short, data[64]);
         for (j=0; j < z->img_mcu_y; ++j) {
            for (i=0; i < z->img_mcu_x; ++i) {
               // scan an interleaved mcu... process scan_n components in order
               for (k=0; k < z->scan_n; ++k) {
                  int n = z->order[k];
                  // scan out an mcu's worth of this component; that's just determined
                  // by the basic H and V specified for the component
                  for (y=0; y < z->img_comp[n].v; ++y) {
                     for (x=0; x < z->img_comp[n].h; ++x) {
                        int x2 = (i*z->img_comp[n].h + x)*8;
                        int y2 = (j*z->img_comp[n].v + y)*8;
                        int ha = z->img_comp[n].ha;
                        if (!pdi__jpeg_decode_block(z, data, z->huff_dc+z->img_comp[n].hd, z->huff_ac+ha, z->fast_ac[ha], n, z->dequant[z->img_comp[n].tq])) return 0;
                        z->idct_block_kernel(z->img_comp[n].data+z->img_comp[n].w2*y2+x2, z->img_comp[n].w2, data);
                     }
                  }
               }
               // after all interleaved components, that's an interleaved MCU,
               // so now count down the restart interval
               if (--z->todo <= 0) {
                  if (z->code_bits < 24) pdi__grow_buffer_unsafe(z);
                  if (!PDI__RESTART(z->marker)) return 1;
                  pdi__jpeg_reset(z);
               }
            }
         }
         return 1;
      }
   } else {
      if (z->scan_n == 1) {
         int i,j;
         int n = z->order[0];
         // non-interleaved data, we just need to process one block at a time,
         // in trivial scanline order
         // number of blocks to do just depends on how many actual "pixels" this
         // component has, independent of interleaved MCU blocking and such
         int w = (z->img_comp[n].x+7) >> 3;
         int h = (z->img_comp[n].y+7) >> 3;
         for (j=0; j < h; ++j) {
            for (i=0; i < w; ++i) {
               short *data = z->img_comp[n].coeff + 64 * (i + j * z->img_comp[n].coeff_w);
               if (z->spec_start == 0) {
                  if (!pdi__jpeg_decode_block_prog_dc(z, data, &z->huff_dc[z->img_comp[n].hd], n))
                     return 0;
               } else {
                  int ha = z->img_comp[n].ha;
                  if (!pdi__jpeg_decode_block_prog_ac(z, data, &z->huff_ac[ha], z->fast_ac[ha]))
                     return 0;
               }
               // every data block is an MCU, so countdown the restart interval
               if (--z->todo <= 0) {
                  if (z->code_bits < 24) pdi__grow_buffer_unsafe(z);
                  if (!PDI__RESTART(z->marker)) return 1;
                  pdi__jpeg_reset(z);
               }
            }
         }
         return 1;
      } else { // interleaved
         int i,j,k,x,y;
         for (j=0; j < z->img_mcu_y; ++j) {
            for (i=0; i < z->img_mcu_x; ++i) {
               // scan an interleaved mcu... process scan_n components in order
               for (k=0; k < z->scan_n; ++k) {
                  int n = z->order[k];
                  // scan out an mcu's worth of this component; that's just determined
                  // by the basic H and V specified for the component
                  for (y=0; y < z->img_comp[n].v; ++y) {
                     for (x=0; x < z->img_comp[n].h; ++x) {
                        int x2 = (i*z->img_comp[n].h + x);
                        int y2 = (j*z->img_comp[n].v + y);
                        short *data = z->img_comp[n].coeff + 64 * (x2 + y2 * z->img_comp[n].coeff_w);
                        if (!pdi__jpeg_decode_block_prog_dc(z, data, &z->huff_dc[z->img_comp[n].hd], n))
                           return 0;
                     }
                  }
               }
               // after all interleaved components, that's an interleaved MCU,
               // so now count down the restart interval
               if (--z->todo <= 0) {
                  if (z->code_bits < 24) pdi__grow_buffer_unsafe(z);
                  if (!PDI__RESTART(z->marker)) return 1;
                  pdi__jpeg_reset(z);
               }
            }
         }
         return 1;
      }
   }
}

static void pdi__jpeg_dequantize(short *data, pdi__uint16 *dequant)
{
   int i;
   for (i=0; i < 64; ++i)
      data[i] *= dequant[i];
}

static void pdi__jpeg_finish(pdi__jpeg *z)
{
   if (z->progressive) {
      // dequantize and idct the data
      int i,j,n;
      for (n=0; n < z->s->img_n; ++n) {
         int w = (z->img_comp[n].x+7) >> 3;
         int h = (z->img_comp[n].y+7) >> 3;
         for (j=0; j < h; ++j) {
            for (i=0; i < w; ++i) {
               short *data = z->img_comp[n].coeff + 64 * (i + j * z->img_comp[n].coeff_w);
               pdi__jpeg_dequantize(data, z->dequant[z->img_comp[n].tq]);
               z->idct_block_kernel(z->img_comp[n].data+z->img_comp[n].w2*j*8+i*8, z->img_comp[n].w2, data);
            }
         }
      }
   }
}

static int pdi__process_marker(pdi__jpeg *z, int m)
{
   int L;
   switch (m) {
      case PDI__MARKER_none: // no marker found
         return pdi__err("expected marker","Corrupt JPEG");

      case 0xDD: // DRI - specify restart interval
         if (pdi__get16be(z->s) != 4) return pdi__err("bad DRI len","Corrupt JPEG");
         z->restart_interval = pdi__get16be(z->s);
         return 1;

      case 0xDB: // DQT - define quantization table
         L = pdi__get16be(z->s)-2;
         while (L > 0) {
            int q = pdi__get8(z->s);
            int p = q >> 4, sixteen = (p != 0);
            int t = q & 15,i;
            if (p != 0 && p != 1) return pdi__err("bad DQT type","Corrupt JPEG");
            if (t > 3) return pdi__err("bad DQT table","Corrupt JPEG");

            for (i=0; i < 64; ++i)
               z->dequant[t][pdi__jpeg_dezigzag[i]] = (pdi__uint16)(sixteen ? pdi__get16be(z->s) : pdi__get8(z->s));
            L -= (sixteen ? 129 : 65);
         }
         return L==0;

      case 0xC4: // DHT - define huffman table
         L = pdi__get16be(z->s)-2;
         while (L > 0) {
            pdi_uc *v;
            int sizes[16],i,n=0;
            int q = pdi__get8(z->s);
            int tc = q >> 4;
            int th = q & 15;
            if (tc > 1 || th > 3) return pdi__err("bad DHT header","Corrupt JPEG");
            for (i=0; i < 16; ++i) {
               sizes[i] = pdi__get8(z->s);
               n += sizes[i];
            }
            if(n > 256) return pdi__err("bad DHT header","Corrupt JPEG"); // Loop over i < n would write past end of values!
            L -= 17;
            if (tc == 0) {
               if (!pdi__build_huffman(z->huff_dc+th, sizes)) return 0;
               v = z->huff_dc[th].values;
            } else {
               if (!pdi__build_huffman(z->huff_ac+th, sizes)) return 0;
               v = z->huff_ac[th].values;
            }
            for (i=0; i < n; ++i)
               v[i] = pdi__get8(z->s);
            if (tc != 0)
               pdi__build_fast_ac(z->fast_ac[th], z->huff_ac + th);
            L -= n;
         }
         return L==0;
   }

   // check for comment block or APP blocks
   if ((m >= 0xE0 && m <= 0xEF) || m == 0xFE) {
      L = pdi__get16be(z->s);
      if (L < 2) {
         if (m == 0xFE)
            return pdi__err("bad COM len","Corrupt JPEG");
         else
            return pdi__err("bad APP len","Corrupt JPEG");
      }
      L -= 2;

      if (m == 0xE0 && L >= 5) { // JFIF APP0 segment
         static const unsigned char tag[5] = {'J','F','I','F','\0'};
         int ok = 1;
         int i;
         for (i=0; i < 5; ++i)
            if (pdi__get8(z->s) != tag[i])
               ok = 0;
         L -= 5;
         if (ok)
            z->jfif = 1;
      } else if (m == 0xEE && L >= 12) { // Adobe APP14 segment
         static const unsigned char tag[6] = {'A','d','o','b','e','\0'};
         int ok = 1;
         int i;
         for (i=0; i < 6; ++i)
            if (pdi__get8(z->s) != tag[i])
               ok = 0;
         L -= 6;
         if (ok) {
            pdi__get8(z->s); // version
            pdi__get16be(z->s); // flags0
            pdi__get16be(z->s); // flags1
            z->app14_color_transform = pdi__get8(z->s); // color transform
            L -= 6;
         }
      }

      pdi__skip(z->s, L);
      return 1;
   }

   return pdi__err("unknown marker","Corrupt JPEG");
}

// after we see SOS
static int pdi__process_scan_header(pdi__jpeg *z)
{
   int i;
   int Ls = pdi__get16be(z->s);
   z->scan_n = pdi__get8(z->s);
   if (z->scan_n < 1 || z->scan_n > 4 || z->scan_n > (int) z->s->img_n) return pdi__err("bad SOS component count","Corrupt JPEG");
   if (Ls != 6+2*z->scan_n) return pdi__err("bad SOS len","Corrupt JPEG");
   for (i=0; i < z->scan_n; ++i) {
      int id = pdi__get8(z->s), which;
      int q = pdi__get8(z->s);
      for (which = 0; which < z->s->img_n; ++which)
         if (z->img_comp[which].id == id)
            break;
      if (which == z->s->img_n) return 0; // no match
      z->img_comp[which].hd = q >> 4;   if (z->img_comp[which].hd > 3) return pdi__err("bad DC huff","Corrupt JPEG");
      z->img_comp[which].ha = q & 15;   if (z->img_comp[which].ha > 3) return pdi__err("bad AC huff","Corrupt JPEG");
      z->order[i] = which;
   }

   {
      int aa;
      z->spec_start = pdi__get8(z->s);
      z->spec_end   = pdi__get8(z->s); // should be 63, but might be 0
      aa = pdi__get8(z->s);
      z->succ_high = (aa >> 4);
      z->succ_low  = (aa & 15);
      if (z->progressive) {
         if (z->spec_start > 63 || z->spec_end > 63  || z->spec_start > z->spec_end || z->succ_high > 13 || z->succ_low > 13)
            return pdi__err("bad SOS", "Corrupt JPEG");
      } else {
         if (z->spec_start != 0) return pdi__err("bad SOS","Corrupt JPEG");
         if (z->succ_high != 0 || z->succ_low != 0) return pdi__err("bad SOS","Corrupt JPEG");
         z->spec_end = 63;
      }
   }

   return 1;
}

static int pdi__free_jpeg_components(pdi__jpeg *z, int ncomp, int why)
{
   int i;
   for (i=0; i < ncomp; ++i) {
      if (z->img_comp[i].raw_data) {
         PDI_FREE(z->img_comp[i].raw_data);
         z->img_comp[i].raw_data = NULL;
         z->img_comp[i].data = NULL;
      }
      if (z->img_comp[i].raw_coeff) {
         PDI_FREE(z->img_comp[i].raw_coeff);
         z->img_comp[i].raw_coeff = 0;
         z->img_comp[i].coeff = 0;
      }
      if (z->img_comp[i].linebuf) {
         PDI_FREE(z->img_comp[i].linebuf);
         z->img_comp[i].linebuf = NULL;
      }
   }
   return why;
}

static int pdi__process_frame_header(pdi__jpeg *z, int scan)
{
   pdi__context *s = z->s;
   int Lf,p,i,q, h_max=1,v_max=1,c;
   Lf = pdi__get16be(s);         if (Lf < 11) return pdi__err("bad SOF len","Corrupt JPEG"); // JPEG
   p  = pdi__get8(s);            if (p != 8) return pdi__err("only 8-bit","JPEG format not supported: 8-bit only"); // JPEG baseline
   s->img_y = pdi__get16be(s);   if (s->img_y == 0) return pdi__err("no header height", "JPEG format not supported: delayed height"); // Legal, but we don't handle it--but neither does IJG
   s->img_x = pdi__get16be(s);   if (s->img_x == 0) return pdi__err("0 width","Corrupt JPEG"); // JPEG requires
   if (s->img_y > PDI_MAX_DIMENSIONS) return pdi__err("too large","Very large image (corrupt?)");
   if (s->img_x > PDI_MAX_DIMENSIONS) return pdi__err("too large","Very large image (corrupt?)");
   c = pdi__get8(s);
   if (c != 3 && c != 1 && c != 4) return pdi__err("bad component count","Corrupt JPEG");
   s->img_n = c;
   for (i=0; i < c; ++i) {
      z->img_comp[i].data = NULL;
      z->img_comp[i].linebuf = NULL;
   }

   if (Lf != 8+3*s->img_n) return pdi__err("bad SOF len","Corrupt JPEG");

   z->rgb = 0;
   for (i=0; i < s->img_n; ++i) {
      static const unsigned char rgb[3] = { 'R', 'G', 'B' };
      z->img_comp[i].id = pdi__get8(s);
      if (s->img_n == 3 && z->img_comp[i].id == rgb[i])
         ++z->rgb;
      q = pdi__get8(s);
      z->img_comp[i].h = (q >> 4);  if (!z->img_comp[i].h || z->img_comp[i].h > 4) return pdi__err("bad H","Corrupt JPEG");
      z->img_comp[i].v = q & 15;    if (!z->img_comp[i].v || z->img_comp[i].v > 4) return pdi__err("bad V","Corrupt JPEG");
      z->img_comp[i].tq = pdi__get8(s);  if (z->img_comp[i].tq > 3) return pdi__err("bad TQ","Corrupt JPEG");
   }

   if (scan != PDI__SCAN_load) return 1;

   if (!pdi__mad3sizes_valid(s->img_x, s->img_y, s->img_n, 0)) return pdi__err("too large", "Image too large to decode");

   for (i=0; i < s->img_n; ++i) {
      if (z->img_comp[i].h > h_max) h_max = z->img_comp[i].h;
      if (z->img_comp[i].v > v_max) v_max = z->img_comp[i].v;
   }

   // check that plane subsampling factors are integer ratios; our resamplers can't deal with fractional ratios
   // and I've never seen a non-corrupted JPEG file actually use them
   for (i=0; i < s->img_n; ++i) {
      if (h_max % z->img_comp[i].h != 0) return pdi__err("bad H","Corrupt JPEG");
      if (v_max % z->img_comp[i].v != 0) return pdi__err("bad V","Corrupt JPEG");
   }

   // compute interleaved mcu info
   z->img_h_max = h_max;
   z->img_v_max = v_max;
   z->img_mcu_w = h_max * 8;
   z->img_mcu_h = v_max * 8;
   // these sizes can't be more than 17 bits
   z->img_mcu_x = (s->img_x + z->img_mcu_w-1) / z->img_mcu_w;
   z->img_mcu_y = (s->img_y + z->img_mcu_h-1) / z->img_mcu_h;

   for (i=0; i < s->img_n; ++i) {
      // number of effective pixels (e.g. for non-interleaved MCU)
      z->img_comp[i].x = (s->img_x * z->img_comp[i].h + h_max-1) / h_max;
      z->img_comp[i].y = (s->img_y * z->img_comp[i].v + v_max-1) / v_max;
      // to simplify generation, we'll allocate enough memory to decode
      // the bogus oversized data from using interleaved MCUs and their
      // big blocks (e.g. a 16x16 iMCU on an image of width 33); we won't
      // discard the extra data until colorspace conversion
      //
      // img_mcu_x, img_mcu_y: <=17 bits; comp[i].h and .v are <=4 (checked earlier)
      // so these muls can't overflow with 32-bit ints (which we require)
      z->img_comp[i].w2 = z->img_mcu_x * z->img_comp[i].h * 8;
      z->img_comp[i].h2 = z->img_mcu_y * z->img_comp[i].v * 8;
      z->img_comp[i].coeff = 0;
      z->img_comp[i].raw_coeff = 0;
      z->img_comp[i].linebuf = NULL;
      z->img_comp[i].raw_data = pdi__malloc_mad2(z->img_comp[i].w2, z->img_comp[i].h2, 15);
      if (z->img_comp[i].raw_data == NULL)
         return pdi__free_jpeg_components(z, i+1, pdi__err("outofmem", "Out of memory"));
      // align blocks for idct using mmx/sse
      z->img_comp[i].data = (pdi_uc*) (((size_t) z->img_comp[i].raw_data + 15) & ~15);
      if (z->progressive) {
         // w2, h2 are multiples of 8 (see above)
         z->img_comp[i].coeff_w = z->img_comp[i].w2 / 8;
         z->img_comp[i].coeff_h = z->img_comp[i].h2 / 8;
         z->img_comp[i].raw_coeff = pdi__malloc_mad3(z->img_comp[i].w2, z->img_comp[i].h2, sizeof(short), 15);
         if (z->img_comp[i].raw_coeff == NULL)
            return pdi__free_jpeg_components(z, i+1, pdi__err("outofmem", "Out of memory"));
         z->img_comp[i].coeff = (short*) (((size_t) z->img_comp[i].raw_coeff + 15) & ~15);
      }
   }

   return 1;
}

// use comparisons since in some cases we handle more than one case (e.g. SOF)
#define pdi__DNL(x)         ((x) == 0xdc)
#define pdi__SOI(x)         ((x) == 0xd8)
#define pdi__EOI(x)         ((x) == 0xd9)
#define pdi__SOF(x)         ((x) == 0xc0 || (x) == 0xc1 || (x) == 0xc2)
#define pdi__SOS(x)         ((x) == 0xda)

#define pdi__SOF_progressive(x)   ((x) == 0xc2)

static int pdi__decode_jpeg_header(pdi__jpeg *z, int scan)
{
   int m;
   z->jfif = 0;
   z->app14_color_transform = -1; // valid values are 0,1,2
   z->marker = PDI__MARKER_none; // initialize cached marker to empty
   m = pdi__get_marker(z);
   if (!pdi__SOI(m)) return pdi__err("no SOI","Corrupt JPEG");
   if (scan == PDI__SCAN_type) return 1;
   m = pdi__get_marker(z);
   while (!pdi__SOF(m)) {
      if (!pdi__process_marker(z,m)) return 0;
      m = pdi__get_marker(z);
      while (m == PDI__MARKER_none) {
         // some files have extra padding after their blocks, so ok, we'll scan
         if (pdi__at_eof(z->s)) return pdi__err("no SOF", "Corrupt JPEG");
         m = pdi__get_marker(z);
      }
   }
   z->progressive = pdi__SOF_progressive(m);
   if (!pdi__process_frame_header(z, scan)) return 0;
   return 1;
}

static pdi_uc pdi__skip_jpeg_junk_at_end(pdi__jpeg *j)
{
   // some JPEGs have junk at end, skip over it but if we find what looks
   // like a valid marker, resume there
   while (!pdi__at_eof(j->s)) {
      pdi_uc x = pdi__get8(j->s);
      while (x == 0xff) { // might be a marker
         if (pdi__at_eof(j->s)) return PDI__MARKER_none;
         x = pdi__get8(j->s);
         if (x != 0x00 && x != 0xff) {
            // not a stuffed zero or lead-in to another marker, looks
            // like an actual marker, return it
            return x;
         }
         // stuffed zero has x=0 now which ends the loop, meaning we go
         // back to regular scan loop.
         // repeated 0xff keeps trying to read the next byte of the marker.
      }
   }
   return PDI__MARKER_none;
}

// decode image to YCbCr format
static int pdi__decode_jpeg_image(pdi__jpeg *j)
{
   int m;
   for (m = 0; m < 4; m++) {
      j->img_comp[m].raw_data = NULL;
      j->img_comp[m].raw_coeff = NULL;
   }
   j->restart_interval = 0;
   if (!pdi__decode_jpeg_header(j, PDI__SCAN_load)) return 0;
   m = pdi__get_marker(j);
   while (!pdi__EOI(m)) {
      if (pdi__SOS(m)) {
         if (!pdi__process_scan_header(j)) return 0;
         if (!pdi__parse_entropy_coded_data(j)) return 0;
         if (j->marker == PDI__MARKER_none ) {
         j->marker = pdi__skip_jpeg_junk_at_end(j);
            // if we reach eof without hitting a marker, pdi__get_marker() below will fail and we'll eventually return 0
         }
         m = pdi__get_marker(j);
         if (PDI__RESTART(m))
            m = pdi__get_marker(j);
      } else if (pdi__DNL(m)) {
         int Ld = pdi__get16be(j->s);
         pdi__uint32 NL = pdi__get16be(j->s);
         if (Ld != 4) return pdi__err("bad DNL len", "Corrupt JPEG");
         if (NL != j->s->img_y) return pdi__err("bad DNL height", "Corrupt JPEG");
         m = pdi__get_marker(j);
      } else {
         if (!pdi__process_marker(j, m)) return 1;
         m = pdi__get_marker(j);
      }
   }
   if (j->progressive)
      pdi__jpeg_finish(j);
   return 1;
}

// static jfif-centered resampling (across block boundaries)

typedef pdi_uc *(*resample_row_func)(pdi_uc *out, pdi_uc *in0, pdi_uc *in1,
                                    int w, int hs);

#define pdi__div4(x) ((pdi_uc) ((x) >> 2))

static pdi_uc *resample_row_1(pdi_uc *out, pdi_uc *in_near, pdi_uc *in_far, int w, int hs)
{
   PDI_NOTUSED(out);
   PDI_NOTUSED(in_far);
   PDI_NOTUSED(w);
   PDI_NOTUSED(hs);
   return in_near;
}

static pdi_uc* pdi__resample_row_v_2(pdi_uc *out, pdi_uc *in_near, pdi_uc *in_far, int w, int hs)
{
   // need to generate two samples vertically for every one in input
   int i;
   PDI_NOTUSED(hs);
   for (i=0; i < w; ++i)
      out[i] = pdi__div4(3*in_near[i] + in_far[i] + 2);
   return out;
}

static pdi_uc*  pdi__resample_row_h_2(pdi_uc *out, pdi_uc *in_near, pdi_uc *in_far, int w, int hs)
{
   // need to generate two samples horizontally for every one in input
   int i;
   pdi_uc *input = in_near;

   if (w == 1) {
      // if only one sample, can't do any interpolation
      out[0] = out[1] = input[0];
      return out;
   }

   out[0] = input[0];
   out[1] = pdi__div4(input[0]*3 + input[1] + 2);
   for (i=1; i < w-1; ++i) {
      int n = 3*input[i]+2;
      out[i*2+0] = pdi__div4(n+input[i-1]);
      out[i*2+1] = pdi__div4(n+input[i+1]);
   }
   out[i*2+0] = pdi__div4(input[w-2]*3 + input[w-1] + 2);
   out[i*2+1] = input[w-1];

   PDI_NOTUSED(in_far);
   PDI_NOTUSED(hs);

   return out;
}

#define pdi__div16(x) ((pdi_uc) ((x) >> 4))

static pdi_uc *pdi__resample_row_hv_2(pdi_uc *out, pdi_uc *in_near, pdi_uc *in_far, int w, int hs)
{
   // need to generate 2x2 samples for every one in input
   int i,t0,t1;
   if (w == 1) {
      out[0] = out[1] = pdi__div4(3*in_near[0] + in_far[0] + 2);
      return out;
   }

   t1 = 3*in_near[0] + in_far[0];
   out[0] = pdi__div4(t1+2);
   for (i=1; i < w; ++i) {
      t0 = t1;
      t1 = 3*in_near[i]+in_far[i];
      out[i*2-1] = pdi__div16(3*t0 + t1 + 8);
      out[i*2  ] = pdi__div16(3*t1 + t0 + 8);
   }
   out[w*2-1] = pdi__div4(t1+2);

   PDI_NOTUSED(hs);

   return out;
}

#if defined(PDI_SSE2) || defined(PDI_NEON)
static pdi_uc *pdi__resample_row_hv_2_simd(pdi_uc *out, pdi_uc *in_near, pdi_uc *in_far, int w, int hs)
{
   // need to generate 2x2 samples for every one in input
   int i=0,t0,t1;

   if (w == 1) {
      out[0] = out[1] = pdi__div4(3*in_near[0] + in_far[0] + 2);
      return out;
   }

   t1 = 3*in_near[0] + in_far[0];
   // process groups of 8 pixels for as long as we can.
   // note we can't handle the last pixel in a row in this loop
   // because we need to handle the filter boundary conditions.
   for (; i < ((w-1) & ~7); i += 8) {
#if defined(PDI_SSE2)
      // load and perform the vertical filtering pass
      // this uses 3*x + y = 4*x + (y - x)
      __m128i zero  = _mm_setzero_si128();
      __m128i farb  = _mm_loadl_epi64((__m128i *) (in_far + i));
      __m128i nearb = _mm_loadl_epi64((__m128i *) (in_near + i));
      __m128i farw  = _mm_unpacklo_epi8(farb, zero);
      __m128i nearw = _mm_unpacklo_epi8(nearb, zero);
      __m128i diff  = _mm_sub_epi16(farw, nearw);
      __m128i nears = _mm_slli_epi16(nearw, 2);
      __m128i curr  = _mm_add_epi16(nears, diff); // current row

      // horizontal filter works the same based on shifted vers of current
      // row. "prev" is current row shifted right by 1 pixel; we need to
      // insert the previous pixel value (from t1).
      // "next" is current row shifted left by 1 pixel, with first pixel
      // of next block of 8 pixels added in.
      __m128i prv0 = _mm_slli_si128(curr, 2);
      __m128i nxt0 = _mm_srli_si128(curr, 2);
      __m128i prev = _mm_insert_epi16(prv0, t1, 0);
      __m128i next = _mm_insert_epi16(nxt0, 3*in_near[i+8] + in_far[i+8], 7);

      // horizontal filter, polyphase implementation since it's convenient:
      // even pixels = 3*cur + prev = cur*4 + (prev - cur)
      // odd  pixels = 3*cur + next = cur*4 + (next - cur)
      // note the shared term.
      __m128i bias  = _mm_set1_epi16(8);
      __m128i curs = _mm_slli_epi16(curr, 2);
      __m128i prvd = _mm_sub_epi16(prev, curr);
      __m128i nxtd = _mm_sub_epi16(next, curr);
      __m128i curb = _mm_add_epi16(curs, bias);
      __m128i even = _mm_add_epi16(prvd, curb);
      __m128i odd  = _mm_add_epi16(nxtd, curb);

      // interleave even and odd pixels, then undo scaling.
      __m128i int0 = _mm_unpacklo_epi16(even, odd);
      __m128i int1 = _mm_unpackhi_epi16(even, odd);
      __m128i de0  = _mm_srli_epi16(int0, 4);
      __m128i de1  = _mm_srli_epi16(int1, 4);

      // pack and write output
      __m128i outv = _mm_packus_epi16(de0, de1);
      _mm_storeu_si128((__m128i *) (out + i*2), outv);
#elif defined(PDI_NEON)
      // load and perform the vertical filtering pass
      // this uses 3*x + y = 4*x + (y - x)
      uint8x8_t farb  = vld1_u8(in_far + i);
      uint8x8_t nearb = vld1_u8(in_near + i);
      int16x8_t diff  = vreinterpretq_s16_u16(vsubl_u8(farb, nearb));
      int16x8_t nears = vreinterpretq_s16_u16(vshll_n_u8(nearb, 2));
      int16x8_t curr  = vaddq_s16(nears, diff); // current row

      // horizontal filter works the same based on shifted vers of current
      // row. "prev" is current row shifted right by 1 pixel; we need to
      // insert the previous pixel value (from t1).
      // "next" is current row shifted left by 1 pixel, with first pixel
      // of next block of 8 pixels added in.
      int16x8_t prv0 = vextq_s16(curr, curr, 7);
      int16x8_t nxt0 = vextq_s16(curr, curr, 1);
      int16x8_t prev = vsetq_lane_s16(t1, prv0, 0);
      int16x8_t next = vsetq_lane_s16(3*in_near[i+8] + in_far[i+8], nxt0, 7);

      // horizontal filter, polyphase implementation since it's convenient:
      // even pixels = 3*cur + prev = cur*4 + (prev - cur)
      // odd  pixels = 3*cur + next = cur*4 + (next - cur)
      // note the shared term.
      int16x8_t curs = vshlq_n_s16(curr, 2);
      int16x8_t prvd = vsubq_s16(prev, curr);
      int16x8_t nxtd = vsubq_s16(next, curr);
      int16x8_t even = vaddq_s16(curs, prvd);
      int16x8_t odd  = vaddq_s16(curs, nxtd);

      // undo scaling and round, then store with even/odd phases interleaved
      uint8x8x2_t o;
      o.val[0] = vqrshrun_n_s16(even, 4);
      o.val[1] = vqrshrun_n_s16(odd,  4);
      vst2_u8(out + i*2, o);
#endif

      // "previous" value for next iter
      t1 = 3*in_near[i+7] + in_far[i+7];
   }

   t0 = t1;
   t1 = 3*in_near[i] + in_far[i];
   out[i*2] = pdi__div16(3*t1 + t0 + 8);

   for (++i; i < w; ++i) {
      t0 = t1;
      t1 = 3*in_near[i]+in_far[i];
      out[i*2-1] = pdi__div16(3*t0 + t1 + 8);
      out[i*2  ] = pdi__div16(3*t1 + t0 + 8);
   }
   out[w*2-1] = pdi__div4(t1+2);

   PDI_NOTUSED(hs);

   return out;
}
#endif

static pdi_uc *pdi__resample_row_generic(pdi_uc *out, pdi_uc *in_near, pdi_uc *in_far, int w, int hs)
{
   // resample with nearest-neighbor
   int i,j;
   PDI_NOTUSED(in_far);
   for (i=0; i < w; ++i)
      for (j=0; j < hs; ++j)
         out[i*hs+j] = in_near[i];
   return out;
}

// this is a reduced-precision calculation of YCbCr-to-RGB introduced
// to make sure the code produces the same results in both SIMD and scalar
#define pdi__float2fixed(x)  (((int) ((x) * 4096.0f + 0.5f)) << 8)
static void pdi__YCbCr_to_RGB_row(pdi_uc *out, const pdi_uc *y, const pdi_uc *pcb, const pdi_uc *pcr, int count, int step)
{
   int i;
   for (i=0; i < count; ++i) {
      int y_fixed = (y[i] << 20) + (1<<19); // rounding
      int r,g,b;
      int cr = pcr[i] - 128;
      int cb = pcb[i] - 128;
      r = y_fixed +  cr* pdi__float2fixed(1.40200f);
      g = y_fixed + (cr*-pdi__float2fixed(0.71414f)) + ((cb*-pdi__float2fixed(0.34414f)) & 0xffff0000);
      b = y_fixed                                     +   cb* pdi__float2fixed(1.77200f);
      r >>= 20;
      g >>= 20;
      b >>= 20;
      if ((unsigned) r > 255) { if (r < 0) r = 0; else r = 255; }
      if ((unsigned) g > 255) { if (g < 0) g = 0; else g = 255; }
      if ((unsigned) b > 255) { if (b < 0) b = 0; else b = 255; }
      out[0] = (pdi_uc)r;
      out[1] = (pdi_uc)g;
      out[2] = (pdi_uc)b;
      out[3] = 255;
      out += step;
   }
}

#if defined(PDI_SSE2) || defined(PDI_NEON)
static void pdi__YCbCr_to_RGB_simd(pdi_uc *out, pdi_uc const *y, pdi_uc const *pcb, pdi_uc const *pcr, int count, int step)
{
   int i = 0;

#ifdef PDI_SSE2
   // step == 3 is pretty ugly on the final interleave, and i'm not convinced
   // it's useful in practice (you wouldn't use it for textures, for example).
   // so just accelerate step == 4 case.
   if (step == 4) {
      // this is a fairly straightforward implementation and not super-optimized.
      __m128i signflip  = _mm_set1_epi8(-0x80);
      __m128i cr_const0 = _mm_set1_epi16(   (short) ( 1.40200f*4096.0f+0.5f));
      __m128i cr_const1 = _mm_set1_epi16( - (short) ( 0.71414f*4096.0f+0.5f));
      __m128i cb_const0 = _mm_set1_epi16( - (short) ( 0.34414f*4096.0f+0.5f));
      __m128i cb_const1 = _mm_set1_epi16(   (short) ( 1.77200f*4096.0f+0.5f));
      __m128i y_bias = _mm_set1_epi8((char) (unsigned char) 128);
      __m128i xw = _mm_set1_epi16(255); // alpha channel

      for (; i+7 < count; i += 8) {
         // load
         __m128i y_bytes = _mm_loadl_epi64((__m128i *) (y+i));
         __m128i cr_bytes = _mm_loadl_epi64((__m128i *) (pcr+i));
         __m128i cb_bytes = _mm_loadl_epi64((__m128i *) (pcb+i));
         __m128i cr_biased = _mm_xor_si128(cr_bytes, signflip); // -128
         __m128i cb_biased = _mm_xor_si128(cb_bytes, signflip); // -128

         // unpack to short (and left-shift cr, cb by 8)
         __m128i yw  = _mm_unpacklo_epi8(y_bias, y_bytes);
         __m128i crw = _mm_unpacklo_epi8(_mm_setzero_si128(), cr_biased);
         __m128i cbw = _mm_unpacklo_epi8(_mm_setzero_si128(), cb_biased);

         // color transform
         __m128i yws = _mm_srli_epi16(yw, 4);
         __m128i cr0 = _mm_mulhi_epi16(cr_const0, crw);
         __m128i cb0 = _mm_mulhi_epi16(cb_const0, cbw);
         __m128i cb1 = _mm_mulhi_epi16(cbw, cb_const1);
         __m128i cr1 = _mm_mulhi_epi16(crw, cr_const1);
         __m128i rws = _mm_add_epi16(cr0, yws);
         __m128i gwt = _mm_add_epi16(cb0, yws);
         __m128i bws = _mm_add_epi16(yws, cb1);
         __m128i gws = _mm_add_epi16(gwt, cr1);

         // descale
         __m128i rw = _mm_srai_epi16(rws, 4);
         __m128i bw = _mm_srai_epi16(bws, 4);
         __m128i gw = _mm_srai_epi16(gws, 4);

         // back to byte, set up for transpose
         __m128i brb = _mm_packus_epi16(rw, bw);
         __m128i gxb = _mm_packus_epi16(gw, xw);

         // transpose to interleave channels
         __m128i t0 = _mm_unpacklo_epi8(brb, gxb);
         __m128i t1 = _mm_unpackhi_epi8(brb, gxb);
         __m128i o0 = _mm_unpacklo_epi16(t0, t1);
         __m128i o1 = _mm_unpackhi_epi16(t0, t1);

         // store
         _mm_storeu_si128((__m128i *) (out + 0), o0);
         _mm_storeu_si128((__m128i *) (out + 16), o1);
         out += 32;
      }
   }
#endif

#ifdef PDI_NEON
   // in this version, step=3 support would be easy to add. but is there demand?
   if (step == 4) {
      // this is a fairly straightforward implementation and not super-optimized.
      uint8x8_t signflip = vdup_n_u8(0x80);
      int16x8_t cr_const0 = vdupq_n_s16(   (short) ( 1.40200f*4096.0f+0.5f));
      int16x8_t cr_const1 = vdupq_n_s16( - (short) ( 0.71414f*4096.0f+0.5f));
      int16x8_t cb_const0 = vdupq_n_s16( - (short) ( 0.34414f*4096.0f+0.5f));
      int16x8_t cb_const1 = vdupq_n_s16(   (short) ( 1.77200f*4096.0f+0.5f));

      for (; i+7 < count; i += 8) {
         // load
         uint8x8_t y_bytes  = vld1_u8(y + i);
         uint8x8_t cr_bytes = vld1_u8(pcr + i);
         uint8x8_t cb_bytes = vld1_u8(pcb + i);
         int8x8_t cr_biased = vreinterpret_s8_u8(vsub_u8(cr_bytes, signflip));
         int8x8_t cb_biased = vreinterpret_s8_u8(vsub_u8(cb_bytes, signflip));

         // expand to s16
         int16x8_t yws = vreinterpretq_s16_u16(vshll_n_u8(y_bytes, 4));
         int16x8_t crw = vshll_n_s8(cr_biased, 7);
         int16x8_t cbw = vshll_n_s8(cb_biased, 7);

         // color transform
         int16x8_t cr0 = vqdmulhq_s16(crw, cr_const0);
         int16x8_t cb0 = vqdmulhq_s16(cbw, cb_const0);
         int16x8_t cr1 = vqdmulhq_s16(crw, cr_const1);
         int16x8_t cb1 = vqdmulhq_s16(cbw, cb_const1);
         int16x8_t rws = vaddq_s16(yws, cr0);
         int16x8_t gws = vaddq_s16(vaddq_s16(yws, cb0), cr1);
         int16x8_t bws = vaddq_s16(yws, cb1);

         // undo scaling, round, convert to byte
         uint8x8x4_t o;
         o.val[0] = vqrshrun_n_s16(rws, 4);
         o.val[1] = vqrshrun_n_s16(gws, 4);
         o.val[2] = vqrshrun_n_s16(bws, 4);
         o.val[3] = vdup_n_u8(255);

         // store, interleaving r/g/b/a
         vst4_u8(out, o);
         out += 8*4;
      }
   }
#endif

   for (; i < count; ++i) {
      int y_fixed = (y[i] << 20) + (1<<19); // rounding
      int r,g,b;
      int cr = pcr[i] - 128;
      int cb = pcb[i] - 128;
      r = y_fixed + cr* pdi__float2fixed(1.40200f);
      g = y_fixed + cr*-pdi__float2fixed(0.71414f) + ((cb*-pdi__float2fixed(0.34414f)) & 0xffff0000);
      b = y_fixed                                   +   cb* pdi__float2fixed(1.77200f);
      r >>= 20;
      g >>= 20;
      b >>= 20;
      if ((unsigned) r > 255) { if (r < 0) r = 0; else r = 255; }
      if ((unsigned) g > 255) { if (g < 0) g = 0; else g = 255; }
      if ((unsigned) b > 255) { if (b < 0) b = 0; else b = 255; }
      out[0] = (pdi_uc)r;
      out[1] = (pdi_uc)g;
      out[2] = (pdi_uc)b;
      out[3] = 255;
      out += step;
   }
}
#endif

// set up the kernels
static void pdi__setup_jpeg(pdi__jpeg *j)
{
   j->idct_block_kernel = pdi__idct_block;
   j->YCbCr_to_RGB_kernel = pdi__YCbCr_to_RGB_row;
   j->resample_row_hv_2_kernel = pdi__resample_row_hv_2;

#ifdef PDI_SSE2
   if (pdi__sse2_available()) {
      j->idct_block_kernel = pdi__idct_simd;
      j->YCbCr_to_RGB_kernel = pdi__YCbCr_to_RGB_simd;
      j->resample_row_hv_2_kernel = pdi__resample_row_hv_2_simd;
   }
#endif

#ifdef PDI_NEON
   j->idct_block_kernel = pdi__idct_simd;
   j->YCbCr_to_RGB_kernel = pdi__YCbCr_to_RGB_simd;
   j->resample_row_hv_2_kernel = pdi__resample_row_hv_2_simd;
#endif
}

// clean up the temporary component buffers
static void pdi__cleanup_jpeg(pdi__jpeg *j)
{
   pdi__free_jpeg_components(j, j->s->img_n, 0);
}

typedef struct
{
   resample_row_func resample;
   pdi_uc *line0,*line1;
   int hs,vs;   // expansion factor in each axis
   int w_lores; // horizontal pixels pre-expansion
   int ystep;   // how far through vertical expansion we are
   int ypos;    // which pre-expansion row we're on
} pdi__resample;

// fast 0..255 * 0..255 => 0..255 rounded multiplication
static pdi_uc pdi__blinn_8x8(pdi_uc x, pdi_uc y)
{
   unsigned int t = x*y + 128;
   return (pdi_uc) ((t + (t >>8)) >> 8);
}

static pdi_uc *load_jpeg_image(pdi__jpeg *z, int *out_x, int *out_y, int *comp, int req_comp)
{
   int n, decode_n, is_rgb;
   z->s->img_n = 0; // make pdi__cleanup_jpeg safe

   // validate req_comp
   if (req_comp < 0 || req_comp > 4) return pdi__errpuc("bad req_comp", "Internal error");

   // load a jpeg image from whichever source, but leave in YCbCr format
   if (!pdi__decode_jpeg_image(z)) { pdi__cleanup_jpeg(z); return NULL; }

   // determine actual number of components to generate
   n = req_comp ? req_comp : z->s->img_n >= 3 ? 3 : 1;

   is_rgb = z->s->img_n == 3 && (z->rgb == 3 || (z->app14_color_transform == 0 && !z->jfif));

   if (z->s->img_n == 3 && n < 3 && !is_rgb)
      decode_n = 1;
   else
      decode_n = z->s->img_n;

   // nothing to do if no components requested; check this now to avoid
   // accessing uninitialized coutput[0] later
   if (decode_n <= 0) { pdi__cleanup_jpeg(z); return NULL; }

   // resample and color-convert
   {
      int k;
      unsigned int i,j;
      pdi_uc *output;
      pdi_uc *coutput[4] = { NULL, NULL, NULL, NULL };

      pdi__resample res_comp[4];

      for (k=0; k < decode_n; ++k) {
         pdi__resample *r = &res_comp[k];

         // allocate line buffer big enough for upsampling off the edges
         // with upsample factor of 4
         z->img_comp[k].linebuf = (pdi_uc *) pdi__malloc(z->s->img_x + 3);
         if (!z->img_comp[k].linebuf) { pdi__cleanup_jpeg(z); return pdi__errpuc("outofmem", "Out of memory"); }

         r->hs      = z->img_h_max / z->img_comp[k].h;
         r->vs      = z->img_v_max / z->img_comp[k].v;
         r->ystep   = r->vs >> 1;
         r->w_lores = (z->s->img_x + r->hs-1) / r->hs;
         r->ypos    = 0;
         r->line0   = r->line1 = z->img_comp[k].data;

         if      (r->hs == 1 && r->vs == 1) r->resample = resample_row_1;
         else if (r->hs == 1 && r->vs == 2) r->resample = pdi__resample_row_v_2;
         else if (r->hs == 2 && r->vs == 1) r->resample = pdi__resample_row_h_2;
         else if (r->hs == 2 && r->vs == 2) r->resample = z->resample_row_hv_2_kernel;
         else                               r->resample = pdi__resample_row_generic;
      }

      // can't error after this so, this is safe
      output = (pdi_uc *) pdi__malloc_mad3(n, z->s->img_x, z->s->img_y, 1);
      if (!output) { pdi__cleanup_jpeg(z); return pdi__errpuc("outofmem", "Out of memory"); }

      // now go ahead and resample
      for (j=0; j < z->s->img_y; ++j) {
         pdi_uc *out = output + n * z->s->img_x * j;
         for (k=0; k < decode_n; ++k) {
            pdi__resample *r = &res_comp[k];
            int y_bot = r->ystep >= (r->vs >> 1);
            coutput[k] = r->resample(z->img_comp[k].linebuf,
                                     y_bot ? r->line1 : r->line0,
                                     y_bot ? r->line0 : r->line1,
                                     r->w_lores, r->hs);
            if (++r->ystep >= r->vs) {
               r->ystep = 0;
               r->line0 = r->line1;
               if (++r->ypos < z->img_comp[k].y)
                  r->line1 += z->img_comp[k].w2;
            }
         }
         if (n >= 3) {
            pdi_uc *y = coutput[0];
            if (z->s->img_n == 3) {
               if (is_rgb) {
                  for (i=0; i < z->s->img_x; ++i) {
                     out[0] = y[i];
                     out[1] = coutput[1][i];
                     out[2] = coutput[2][i];
                     out[3] = 255;
                     out += n;
                  }
               } else {
                  z->YCbCr_to_RGB_kernel(out, y, coutput[1], coutput[2], z->s->img_x, n);
               }
            } else if (z->s->img_n == 4) {
               if (z->app14_color_transform == 0) { // CMYK
                  for (i=0; i < z->s->img_x; ++i) {
                     pdi_uc m = coutput[3][i];
                     out[0] = pdi__blinn_8x8(coutput[0][i], m);
                     out[1] = pdi__blinn_8x8(coutput[1][i], m);
                     out[2] = pdi__blinn_8x8(coutput[2][i], m);
                     out[3] = 255;
                     out += n;
                  }
               } else if (z->app14_color_transform == 2) { // YCCK
                  z->YCbCr_to_RGB_kernel(out, y, coutput[1], coutput[2], z->s->img_x, n);
                  for (i=0; i < z->s->img_x; ++i) {
                     pdi_uc m = coutput[3][i];
                     out[0] = pdi__blinn_8x8(255 - out[0], m);
                     out[1] = pdi__blinn_8x8(255 - out[1], m);
                     out[2] = pdi__blinn_8x8(255 - out[2], m);
                     out += n;
                  }
               } else { // YCbCr + alpha?  Ignore the fourth channel for now
                  z->YCbCr_to_RGB_kernel(out, y, coutput[1], coutput[2], z->s->img_x, n);
               }
            } else
               for (i=0; i < z->s->img_x; ++i) {
                  out[0] = out[1] = out[2] = y[i];
                  out[3] = 255; // not used if n==3
                  out += n;
               }
         } else {
            if (is_rgb) {
               if (n == 1)
                  for (i=0; i < z->s->img_x; ++i)
                     *out++ = pdi__compute_y(coutput[0][i], coutput[1][i], coutput[2][i]);
               else {
                  for (i=0; i < z->s->img_x; ++i, out += 2) {
                     out[0] = pdi__compute_y(coutput[0][i], coutput[1][i], coutput[2][i]);
                     out[1] = 255;
                  }
               }
            } else if (z->s->img_n == 4 && z->app14_color_transform == 0) {
               for (i=0; i < z->s->img_x; ++i) {
                  pdi_uc m = coutput[3][i];
                  pdi_uc r = pdi__blinn_8x8(coutput[0][i], m);
                  pdi_uc g = pdi__blinn_8x8(coutput[1][i], m);
                  pdi_uc b = pdi__blinn_8x8(coutput[2][i], m);
                  out[0] = pdi__compute_y(r, g, b);
                  out[1] = 255;
                  out += n;
               }
            } else if (z->s->img_n == 4 && z->app14_color_transform == 2) {
               for (i=0; i < z->s->img_x; ++i) {
                  out[0] = pdi__blinn_8x8(255 - coutput[0][i], coutput[3][i]);
                  out[1] = 255;
                  out += n;
               }
            } else {
               pdi_uc *y = coutput[0];
               if (n == 1)
                  for (i=0; i < z->s->img_x; ++i) out[i] = y[i];
               else
                  for (i=0; i < z->s->img_x; ++i) { *out++ = y[i]; *out++ = 255; }
            }
         }
      }
      pdi__cleanup_jpeg(z);
      *out_x = z->s->img_x;
      *out_y = z->s->img_y;
      if (comp) *comp = z->s->img_n >= 3 ? 3 : 1; // report original components, not output
      return output;
   }
}

static void *pdi__jpeg_load(pdi__context *s, int *x, int *y, int *comp, int req_comp, pdi__result_info *ri)
{
   unsigned char* result;
   pdi__jpeg* j = (pdi__jpeg*) pdi__malloc(sizeof(pdi__jpeg));
   if (!j) return pdi__errpuc("outofmem", "Out of memory");
   memset(j, 0, sizeof(pdi__jpeg));
   PDI_NOTUSED(ri);
   j->s = s;
   pdi__setup_jpeg(j);
   result = load_jpeg_image(j, x,y,comp,req_comp);
   PDI_FREE(j);
   return result;
}

static int pdi__jpeg_test(pdi__context *s)
{
   int r;
   pdi__jpeg* j = (pdi__jpeg*)pdi__malloc(sizeof(pdi__jpeg));
   if (!j) return pdi__err("outofmem", "Out of memory");
   memset(j, 0, sizeof(pdi__jpeg));
   j->s = s;
   pdi__setup_jpeg(j);
   r = pdi__decode_jpeg_header(j, PDI__SCAN_type);
   pdi__rewind(s);
   PDI_FREE(j);
   return r;
}

static int pdi__jpeg_info_raw(pdi__jpeg *j, int *x, int *y, int *comp)
{
   if (!pdi__decode_jpeg_header(j, PDI__SCAN_header)) {
      pdi__rewind( j->s );
      return 0;
   }
   if (x) *x = j->s->img_x;
   if (y) *y = j->s->img_y;
   if (comp) *comp = j->s->img_n >= 3 ? 3 : 1;
   return 1;
}

static int pdi__jpeg_info(pdi__context *s, int *x, int *y, int *comp)
{
   int result;
   pdi__jpeg* j = (pdi__jpeg*) (pdi__malloc(sizeof(pdi__jpeg)));
   if (!j) return pdi__err("outofmem", "Out of memory");
   memset(j, 0, sizeof(pdi__jpeg));
   j->s = s;
   result = pdi__jpeg_info_raw(j, x, y, comp);
   PDI_FREE(j);
   return result;
}
#endif

// public domain zlib decode    v0.2  Sean Barrett 2006-11-18
//    simple implementation
//      - all input must be provided in an upfront buffer
//      - all output is written to a single output buffer (can malloc/realloc)
//    performance
//      - fast huffman

#ifndef PDI_NO_ZLIB

// fast-way is faster to check than jpeg huffman, but slow way is slower
#define PDI__ZFAST_BITS  9 // accelerate all cases in default tables
#define PDI__ZFAST_MASK  ((1 << PDI__ZFAST_BITS) - 1)
#define PDI__ZNSYMS 288 // number of symbols in literal/length alphabet

// zlib-style huffman encoding
// (jpegs packs from left, zlib from right, so can't share code)
typedef struct
{
   pdi__uint16 fast[1 << PDI__ZFAST_BITS];
   pdi__uint16 firstcode[16];
   int maxcode[17];
   pdi__uint16 firstsymbol[16];
   pdi_uc  size[PDI__ZNSYMS];
   pdi__uint16 value[PDI__ZNSYMS];
} pdi__zhuffman;

pdi_inline static int pdi__bitreverse16(int n)
{
  n = ((n & 0xAAAA) >>  1) | ((n & 0x5555) << 1);
  n = ((n & 0xCCCC) >>  2) | ((n & 0x3333) << 2);
  n = ((n & 0xF0F0) >>  4) | ((n & 0x0F0F) << 4);
  n = ((n & 0xFF00) >>  8) | ((n & 0x00FF) << 8);
  return n;
}

pdi_inline static int pdi__bit_reverse(int v, int bits)
{
   PDI_ASSERT(bits <= 16);
   // to bit reverse n bits, reverse 16 and shift
   // e.g. 11 bits, bit reverse and shift away 5
   return pdi__bitreverse16(v) >> (16-bits);
}

static int pdi__zbuild_huffman(pdi__zhuffman *z, const pdi_uc *sizelist, int num)
{
   int i,k=0;
   int code, next_code[16], sizes[17];

   // DEFLATE spec for generating codes
   memset(sizes, 0, sizeof(sizes));
   memset(z->fast, 0, sizeof(z->fast));
   for (i=0; i < num; ++i)
      ++sizes[sizelist[i]];
   sizes[0] = 0;
   for (i=1; i < 16; ++i)
      if (sizes[i] > (1 << i))
         return pdi__err("bad sizes", "Corrupt PNG");
   code = 0;
   for (i=1; i < 16; ++i) {
      next_code[i] = code;
      z->firstcode[i] = (pdi__uint16) code;
      z->firstsymbol[i] = (pdi__uint16) k;
      code = (code + sizes[i]);
      if (sizes[i])
         if (code-1 >= (1 << i)) return pdi__err("bad codelengths","Corrupt PNG");
      z->maxcode[i] = code << (16-i); // preshift for inner loop
      code <<= 1;
      k += sizes[i];
   }
   z->maxcode[16] = 0x10000; // sentinel
   for (i=0; i < num; ++i) {
      int s = sizelist[i];
      if (s) {
         int c = next_code[s] - z->firstcode[s] + z->firstsymbol[s];
         pdi__uint16 fastv = (pdi__uint16) ((s << 9) | i);
         z->size [c] = (pdi_uc     ) s;
         z->value[c] = (pdi__uint16) i;
         if (s <= PDI__ZFAST_BITS) {
            int j = pdi__bit_reverse(next_code[s],s);
            while (j < (1 << PDI__ZFAST_BITS)) {
               z->fast[j] = fastv;
               j += (1 << s);
            }
         }
         ++next_code[s];
      }
   }
   return 1;
}

// zlib-from-memory implementation for PNG reading
//    because PNG allows splitting the zlib stream arbitrarily,
//    and it's annoying structurally to have PNG call ZLIB call PNG,
//    we require PNG read all the IDATs and combine them into a single
//    memory buffer

typedef struct
{
   pdi_uc *zbuffer, *zbuffer_end;
   int num_bits;
   int hit_zeof_once;
   pdi__uint32 code_buffer;

   char *zout;
   char *zout_start;
   char *zout_end;
   int   z_expandable;

   pdi__zhuffman z_length, z_distance;
} pdi__zbuf;

pdi_inline static int pdi__zeof(pdi__zbuf *z)
{
   return (z->zbuffer >= z->zbuffer_end);
}

pdi_inline static pdi_uc pdi__zget8(pdi__zbuf *z)
{
   return pdi__zeof(z) ? 0 : *z->zbuffer++;
}

static void pdi__fill_bits(pdi__zbuf *z)
{
   do {
      if (z->code_buffer >= (1U << z->num_bits)) {
        z->zbuffer = z->zbuffer_end;  /* treat this as EOF so we fail. */
        return;
      }
      z->code_buffer |= (unsigned int) pdi__zget8(z) << z->num_bits;
      z->num_bits += 8;
   } while (z->num_bits <= 24);
}

pdi_inline static unsigned int pdi__zreceive(pdi__zbuf *z, int n)
{
   unsigned int k;
   if (z->num_bits < n) pdi__fill_bits(z);
   k = z->code_buffer & ((1 << n) - 1);
   z->code_buffer >>= n;
   z->num_bits -= n;
   return k;
}

static int pdi__zhuffman_decode_slowpath(pdi__zbuf *a, pdi__zhuffman *z)
{
   int b,s,k;
   // not resolved by fast table, so compute it the slow way
   // use jpeg approach, which requires MSbits at top
   k = pdi__bit_reverse(a->code_buffer, 16);
   for (s=PDI__ZFAST_BITS+1; ; ++s)
      if (k < z->maxcode[s])
         break;
   if (s >= 16) return -1; // invalid code!
   // code size is s, so:
   b = (k >> (16-s)) - z->firstcode[s] + z->firstsymbol[s];
   if (b >= PDI__ZNSYMS) return -1; // some data was corrupt somewhere!
   if (z->size[b] != s) return -1;  // was originally an assert, but report failure instead.
   a->code_buffer >>= s;
   a->num_bits -= s;
   return z->value[b];
}

pdi_inline static int pdi__zhuffman_decode(pdi__zbuf *a, pdi__zhuffman *z)
{
   int b,s;
   if (a->num_bits < 16) {
      if (pdi__zeof(a)) {
         if (!a->hit_zeof_once) {
            // This is the first time we hit eof, insert 16 extra padding btis
            // to allow us to keep going; if we actually consume any of them
            // though, that is invalid data. This is caught later.
            a->hit_zeof_once = 1;
            a->num_bits += 16; // add 16 implicit zero bits
         } else {
            // We already inserted our extra 16 padding bits and are again
            // out, this stream is actually prematurely terminated.
            return -1;
         }
      } else {
         pdi__fill_bits(a);
      }
   }
   b = z->fast[a->code_buffer & PDI__ZFAST_MASK];
   if (b) {
      s = b >> 9;
      a->code_buffer >>= s;
      a->num_bits -= s;
      return b & 511;
   }
   return pdi__zhuffman_decode_slowpath(a, z);
}

static int pdi__zexpand(pdi__zbuf *z, char *zout, int n)  // need to make room for n bytes
{
   char *q;
   unsigned int cur, limit, old_limit;
   z->zout = zout;
   if (!z->z_expandable) return pdi__err("output buffer limit","Corrupt PNG");
   cur   = (unsigned int) (z->zout - z->zout_start);
   limit = old_limit = (unsigned) (z->zout_end - z->zout_start);
   if (UINT_MAX - cur < (unsigned) n) return pdi__err("outofmem", "Out of memory");
   while (cur + n > limit) {
      if(limit > UINT_MAX / 2) return pdi__err("outofmem", "Out of memory");
      limit *= 2;
   }
   q = (char *) PDI_REALLOC_SIZED(z->zout_start, old_limit, limit);
   PDI_NOTUSED(old_limit);
   if (q == NULL) return pdi__err("outofmem", "Out of memory");
   z->zout_start = q;
   z->zout       = q + cur;
   z->zout_end   = q + limit;
   return 1;
}

static const int pdi__zlength_base[31] = {
   3,4,5,6,7,8,9,10,11,13,
   15,17,19,23,27,31,35,43,51,59,
   67,83,99,115,131,163,195,227,258,0,0 };

static const int pdi__zlength_extra[31]=
{ 0,0,0,0,0,0,0,0,1,1,1,1,2,2,2,2,3,3,3,3,4,4,4,4,5,5,5,5,0,0,0 };

static const int pdi__zdist_base[32] = { 1,2,3,4,5,7,9,13,17,25,33,49,65,97,129,193,
257,385,513,769,1025,1537,2049,3073,4097,6145,8193,12289,16385,24577,0,0};

static const int pdi__zdist_extra[32] =
{ 0,0,0,0,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,13,13};

static int pdi__parse_huffman_block(pdi__zbuf *a)
{
   char *zout = a->zout;
   for(;;) {
      int z = pdi__zhuffman_decode(a, &a->z_length);
      if (z < 256) {
         if (z < 0) return pdi__err("bad huffman code","Corrupt PNG"); // error in huffman codes
         if (zout >= a->zout_end) {
            if (!pdi__zexpand(a, zout, 1)) return 0;
            zout = a->zout;
         }
         *zout++ = (char) z;
      } else {
         pdi_uc *p;
         int len,dist;
         if (z == 256) {
            a->zout = zout;
            if (a->hit_zeof_once && a->num_bits < 16) {
               // The first time we hit zeof, we inserted 16 extra zero bits into our bit
               // buffer so the decoder can just do its speculative decoding. But if we
               // actually consumed any of those bits (which is the case when num_bits < 16),
               // the stream actually read past the end so it is malformed.
               return pdi__err("unexpected end","Corrupt PNG");
            }
            return 1;
         }
         if (z >= 286) return pdi__err("bad huffman code","Corrupt PNG"); // per DEFLATE, length codes 286 and 287 must not appear in compressed data
         z -= 257;
         len = pdi__zlength_base[z];
         if (pdi__zlength_extra[z]) len += pdi__zreceive(a, pdi__zlength_extra[z]);
         z = pdi__zhuffman_decode(a, &a->z_distance);
         if (z < 0 || z >= 30) return pdi__err("bad huffman code","Corrupt PNG"); // per DEFLATE, distance codes 30 and 31 must not appear in compressed data
         dist = pdi__zdist_base[z];
         if (pdi__zdist_extra[z]) dist += pdi__zreceive(a, pdi__zdist_extra[z]);
         if (zout - a->zout_start < dist) return pdi__err("bad dist","Corrupt PNG");
         if (len > a->zout_end - zout) {
            if (!pdi__zexpand(a, zout, len)) return 0;
            zout = a->zout;
         }
         p = (pdi_uc *) (zout - dist);
         if (dist == 1) { // run of one byte; common in images.
            pdi_uc v = *p;
            if (len) { do *zout++ = v; while (--len); }
         } else {
            if (len) { do *zout++ = *p++; while (--len); }
         }
      }
   }
}

static int pdi__compute_huffman_codes(pdi__zbuf *a)
{
   static const pdi_uc length_dezigzag[19] = { 16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15 };
   pdi__zhuffman z_codelength;
   pdi_uc lencodes[286+32+137];//padding for maximum single op
   pdi_uc codelength_sizes[19];
   int i,n;

   int hlit  = pdi__zreceive(a,5) + 257;
   int hdist = pdi__zreceive(a,5) + 1;
   int hclen = pdi__zreceive(a,4) + 4;
   int ntot  = hlit + hdist;

   memset(codelength_sizes, 0, sizeof(codelength_sizes));
   for (i=0; i < hclen; ++i) {
      int s = pdi__zreceive(a,3);
      codelength_sizes[length_dezigzag[i]] = (pdi_uc) s;
   }
   if (!pdi__zbuild_huffman(&z_codelength, codelength_sizes, 19)) return 0;

   n = 0;
   while (n < ntot) {
      int c = pdi__zhuffman_decode(a, &z_codelength);
      if (c < 0 || c >= 19) return pdi__err("bad codelengths", "Corrupt PNG");
      if (c < 16)
         lencodes[n++] = (pdi_uc) c;
      else {
         pdi_uc fill = 0;
         if (c == 16) {
            c = pdi__zreceive(a,2)+3;
            if (n == 0) return pdi__err("bad codelengths", "Corrupt PNG");
            fill = lencodes[n-1];
         } else if (c == 17) {
            c = pdi__zreceive(a,3)+3;
         } else if (c == 18) {
            c = pdi__zreceive(a,7)+11;
         } else {
            return pdi__err("bad codelengths", "Corrupt PNG");
         }
         if (ntot - n < c) return pdi__err("bad codelengths", "Corrupt PNG");
         memset(lencodes+n, fill, c);
         n += c;
      }
   }
   if (n != ntot) return pdi__err("bad codelengths","Corrupt PNG");
   if (!pdi__zbuild_huffman(&a->z_length, lencodes, hlit)) return 0;
   if (!pdi__zbuild_huffman(&a->z_distance, lencodes+hlit, hdist)) return 0;
   return 1;
}

static int pdi__parse_uncompressed_block(pdi__zbuf *a)
{
   pdi_uc header[4];
   int len,nlen,k;
   if (a->num_bits & 7)
      pdi__zreceive(a, a->num_bits & 7); // discard
   // drain the bit-packed data into header
   k = 0;
   while (a->num_bits > 0) {
      header[k++] = (pdi_uc) (a->code_buffer & 255); // suppress MSVC run-time check
      a->code_buffer >>= 8;
      a->num_bits -= 8;
   }
   if (a->num_bits < 0) return pdi__err("zlib corrupt","Corrupt PNG");
   // now fill header the normal way
   while (k < 4)
      header[k++] = pdi__zget8(a);
   len  = header[1] * 256 + header[0];
   nlen = header[3] * 256 + header[2];
   if (nlen != (len ^ 0xffff)) return pdi__err("zlib corrupt","Corrupt PNG");
   if (a->zbuffer + len > a->zbuffer_end) return pdi__err("read past buffer","Corrupt PNG");
   if (a->zout + len > a->zout_end)
      if (!pdi__zexpand(a, a->zout, len)) return 0;
   memcpy(a->zout, a->zbuffer, len);
   a->zbuffer += len;
   a->zout += len;
   return 1;
}

static int pdi__parse_zlib_header(pdi__zbuf *a)
{
   int cmf   = pdi__zget8(a);
   int cm    = cmf & 15;
   /* int cinfo = cmf >> 4; */
   int flg   = pdi__zget8(a);
   if (pdi__zeof(a)) return pdi__err("bad zlib header","Corrupt PNG"); // zlib spec
   if ((cmf*256+flg) % 31 != 0) return pdi__err("bad zlib header","Corrupt PNG"); // zlib spec
   if (flg & 32) return pdi__err("no preset dict","Corrupt PNG"); // preset dictionary not allowed in png
   if (cm != 8) return pdi__err("bad compression","Corrupt PNG"); // DEFLATE required for png
   // window = 1 << (8 + cinfo)... but who cares, we fully buffer output
   return 1;
}

static const pdi_uc pdi__zdefault_length[PDI__ZNSYMS] =
{
   8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8, 8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,
   8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8, 8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,
   8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8, 8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,
   8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8, 8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,
   8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8, 9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,
   9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9, 9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,
   9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9, 9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,
   9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9, 9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,
   7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7, 7,7,7,7,7,7,7,7,8,8,8,8,8,8,8,8
};
static const pdi_uc pdi__zdefault_distance[32] =
{
   5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5
};
/*
Init algorithm:
{
   int i;   // use <= to match clearly with spec
   for (i=0; i <= 143; ++i)     pdi__zdefault_length[i]   = 8;
   for (   ; i <= 255; ++i)     pdi__zdefault_length[i]   = 9;
   for (   ; i <= 279; ++i)     pdi__zdefault_length[i]   = 7;
   for (   ; i <= 287; ++i)     pdi__zdefault_length[i]   = 8;

   for (i=0; i <=  31; ++i)     pdi__zdefault_distance[i] = 5;
}
*/

static int pdi__parse_zlib(pdi__zbuf *a, int parse_header)
{
   int final, type;
   if (parse_header)
      if (!pdi__parse_zlib_header(a)) return 0;
   a->num_bits = 0;
   a->code_buffer = 0;
   a->hit_zeof_once = 0;
   do {
      final = pdi__zreceive(a,1);
      type = pdi__zreceive(a,2);
      if (type == 0) {
         if (!pdi__parse_uncompressed_block(a)) return 0;
      } else if (type == 3) {
         return 0;
      } else {
         if (type == 1) {
            // use fixed code lengths
            if (!pdi__zbuild_huffman(&a->z_length  , pdi__zdefault_length  , PDI__ZNSYMS)) return 0;
            if (!pdi__zbuild_huffman(&a->z_distance, pdi__zdefault_distance,  32)) return 0;
         } else {
            if (!pdi__compute_huffman_codes(a)) return 0;
         }
         if (!pdi__parse_huffman_block(a)) return 0;
      }
   } while (!final);
   return 1;
}

static int pdi__do_zlib(pdi__zbuf *a, char *obuf, int olen, int exp, int parse_header)
{
   a->zout_start = obuf;
   a->zout       = obuf;
   a->zout_end   = obuf + olen;
   a->z_expandable = exp;

   return pdi__parse_zlib(a, parse_header);
}

PDIDEF char *pdi_zlib_decode_malloc_guesssize(const char *buffer, int len, int initial_size, int *outlen)
{
   pdi__zbuf a;
   char *p = (char *) pdi__malloc(initial_size);
   if (p == NULL) return NULL;
   a.zbuffer = (pdi_uc *) buffer;
   a.zbuffer_end = (pdi_uc *) buffer + len;
   if (pdi__do_zlib(&a, p, initial_size, 1, 1)) {
      if (outlen) *outlen = (int) (a.zout - a.zout_start);
      return a.zout_start;
   } else {
      PDI_FREE(a.zout_start);
      return NULL;
   }
}

PDIDEF char *pdi_zlib_decode_malloc(char const *buffer, int len, int *outlen)
{
   return pdi_zlib_decode_malloc_guesssize(buffer, len, 16384, outlen);
}

PDIDEF char *pdi_zlib_decode_malloc_guesssize_headerflag(const char *buffer, int len, int initial_size, int *outlen, int parse_header)
{
   pdi__zbuf a;
   char *p = (char *) pdi__malloc(initial_size);
   if (p == NULL) return NULL;
   a.zbuffer = (pdi_uc *) buffer;
   a.zbuffer_end = (pdi_uc *) buffer + len;
   if (pdi__do_zlib(&a, p, initial_size, 1, parse_header)) {
      if (outlen) *outlen = (int) (a.zout - a.zout_start);
      return a.zout_start;
   } else {
      PDI_FREE(a.zout_start);
      return NULL;
   }
}

PDIDEF int pdi_zlib_decode_buffer(char *obuffer, int olen, char const *ibuffer, int ilen)
{
   pdi__zbuf a;
   a.zbuffer = (pdi_uc *) ibuffer;
   a.zbuffer_end = (pdi_uc *) ibuffer + ilen;
   if (pdi__do_zlib(&a, obuffer, olen, 0, 1))
      return (int) (a.zout - a.zout_start);
   else
      return -1;
}

PDIDEF char *pdi_zlib_decode_noheader_malloc(char const *buffer, int len, int *outlen)
{
   pdi__zbuf a;
   char *p = (char *) pdi__malloc(16384);
   if (p == NULL) return NULL;
   a.zbuffer = (pdi_uc *) buffer;
   a.zbuffer_end = (pdi_uc *) buffer+len;
   if (pdi__do_zlib(&a, p, 16384, 1, 0)) {
      if (outlen) *outlen = (int) (a.zout - a.zout_start);
      return a.zout_start;
   } else {
      PDI_FREE(a.zout_start);
      return NULL;
   }
}

PDIDEF int pdi_zlib_decode_noheader_buffer(char *obuffer, int olen, const char *ibuffer, int ilen)
{
   pdi__zbuf a;
   a.zbuffer = (pdi_uc *) ibuffer;
   a.zbuffer_end = (pdi_uc *) ibuffer + ilen;
   if (pdi__do_zlib(&a, obuffer, olen, 0, 0))
      return (int) (a.zout - a.zout_start);
   else
      return -1;
}
#endif

// public domain "baseline" PNG decoder   v0.10  Sean Barrett 2006-11-18
//    simple implementation
//      - only 8-bit samples
//      - no CRC checking
//      - allocates lots of intermediate memory
//        - avoids problem of streaming data between subsystems
//        - avoids explicit window management
//    performance
//      - uses stb_zlib, a PD zlib implementation with fast huffman decoding

#ifndef PDI_NO_PNG
typedef struct
{
   pdi__uint32 length;
   pdi__uint32 type;
} pdi__pngchunk;

static pdi__pngchunk pdi__get_chunk_header(pdi__context *s)
{
   pdi__pngchunk c;
   c.length = pdi__get32be(s);
   c.type   = pdi__get32be(s);
   return c;
}

static int pdi__check_png_header(pdi__context *s)
{
   static const pdi_uc png_sig[8] = { 137,80,78,71,13,10,26,10 };
   int i;
   for (i=0; i < 8; ++i)
      if (pdi__get8(s) != png_sig[i]) return pdi__err("bad png sig","Not a PNG");
   return 1;
}

typedef struct
{
   pdi__context *s;
   pdi_uc *idata, *expanded, *out;
   int depth;
} pdi__png;


enum {
   PDI__F_none=0,
   PDI__F_sub=1,
   PDI__F_up=2,
   PDI__F_avg=3,
   PDI__F_paeth=4,
   // synthetic filter used for first scanline to avoid needing a dummy row of 0s
   PDI__F_avg_first
};

static pdi_uc first_row_filter[5] =
{
   PDI__F_none,
   PDI__F_sub,
   PDI__F_none,
   PDI__F_avg_first,
   PDI__F_sub // Paeth with b=c=0 turns out to be equivalent to sub
};

static int pdi__paeth(int a, int b, int c)
{
   // This formulation looks very different from the reference in the PNG spec, but is
   // actually equivalent and has favorable data dependencies and admits straightforward
   // generation of branch-free code, which helps performance significantly.
   int thresh = c*3 - (a + b);
   int lo = a < b ? a : b;
   int hi = a < b ? b : a;
   int t0 = (hi <= thresh) ? lo : c;
   int t1 = (thresh <= lo) ? hi : t0;
   return t1;
}

static const pdi_uc pdi__depth_scale_table[9] = { 0, 0xff, 0x55, 0, 0x11, 0,0,0, 0x01 };

// adds an extra all-255 alpha channel
// dest == src is legal
// img_n must be 1 or 3
static void pdi__create_png_alpha_expand8(pdi_uc *dest, pdi_uc *src, pdi__uint32 x, int img_n)
{
   int i;
   // must process data backwards since we allow dest==src
   if (img_n == 1) {
      for (i=x-1; i >= 0; --i) {
         dest[i*2+1] = 255;
         dest[i*2+0] = src[i];
      }
   } else {
      PDI_ASSERT(img_n == 3);
      for (i=x-1; i >= 0; --i) {
         dest[i*4+3] = 255;
         dest[i*4+2] = src[i*3+2];
         dest[i*4+1] = src[i*3+1];
         dest[i*4+0] = src[i*3+0];
      }
   }
}

// create the png data from post-deflated data
static int pdi__create_png_image_raw(pdi__png *a, pdi_uc *raw, pdi__uint32 raw_len, int out_n, pdi__uint32 x, pdi__uint32 y, int depth, int color)
{
   int bytes = (depth == 16 ? 2 : 1);
   pdi__context *s = a->s;
   pdi__uint32 i,j,stride = x*out_n*bytes;
   pdi__uint32 img_len, img_width_bytes;
   pdi_uc *filter_buf;
   int all_ok = 1;
   int k;
   int img_n = s->img_n; // copy it into a local for later

   int output_bytes = out_n*bytes;
   int filter_bytes = img_n*bytes;
   int width = x;

   PDI_ASSERT(out_n == s->img_n || out_n == s->img_n+1);
   a->out = (pdi_uc *) pdi__malloc_mad3(x, y, output_bytes, 0); // extra bytes to write off the end into
   if (!a->out) return pdi__err("outofmem", "Out of memory");

   // note: error exits here don't need to clean up a->out individually,
   // pdi__do_png always does on error.
   if (!pdi__mad3sizes_valid(img_n, x, depth, 7)) return pdi__err("too large", "Corrupt PNG");
   img_width_bytes = (((img_n * x * depth) + 7) >> 3);
   if (!pdi__mad2sizes_valid(img_width_bytes, y, img_width_bytes)) return pdi__err("too large", "Corrupt PNG");
   img_len = (img_width_bytes + 1) * y;

   // we used to check for exact match between raw_len and img_len on non-interlaced PNGs,
   // but issue #276 reported a PNG in the wild that had extra data at the end (all zeros),
   // so just check for raw_len < img_len always.
   if (raw_len < img_len) return pdi__err("not enough pixels","Corrupt PNG");

   // Allocate two scan lines worth of filter workspace buffer.
   filter_buf = (pdi_uc *) pdi__malloc_mad2(img_width_bytes, 2, 0);
   if (!filter_buf) return pdi__err("outofmem", "Out of memory");

   // Filtering for low-bit-depth images
   if (depth < 8) {
      filter_bytes = 1;
      width = img_width_bytes;
   }

   for (j=0; j < y; ++j) {
      // cur/prior filter buffers alternate
      pdi_uc *cur = filter_buf + (j & 1)*img_width_bytes;
      pdi_uc *prior = filter_buf + (~j & 1)*img_width_bytes;
      pdi_uc *dest = a->out + stride*j;
      int nk = width * filter_bytes;
      int filter = *raw++;

      // check filter type
      if (filter > 4) {
         all_ok = pdi__err("invalid filter","Corrupt PNG");
         break;
      }

      // if first row, use special filter that doesn't sample previous row
      if (j == 0) filter = first_row_filter[filter];

      // perform actual filtering
      switch (filter) {
      case PDI__F_none:
         memcpy(cur, raw, nk);
         break;
      case PDI__F_sub:
         memcpy(cur, raw, filter_bytes);
         for (k = filter_bytes; k < nk; ++k)
            cur[k] = PDI__BYTECAST(raw[k] + cur[k-filter_bytes]);
         break;
      case PDI__F_up:
         for (k = 0; k < nk; ++k)
            cur[k] = PDI__BYTECAST(raw[k] + prior[k]);
         break;
      case PDI__F_avg:
         for (k = 0; k < filter_bytes; ++k)
            cur[k] = PDI__BYTECAST(raw[k] + (prior[k]>>1));
         for (k = filter_bytes; k < nk; ++k)
            cur[k] = PDI__BYTECAST(raw[k] + ((prior[k] + cur[k-filter_bytes])>>1));
         break;
      case PDI__F_paeth:
         for (k = 0; k < filter_bytes; ++k)
            cur[k] = PDI__BYTECAST(raw[k] + prior[k]); // prior[k] == pdi__paeth(0,prior[k],0)
         for (k = filter_bytes; k < nk; ++k)
            cur[k] = PDI__BYTECAST(raw[k] + pdi__paeth(cur[k-filter_bytes], prior[k], prior[k-filter_bytes]));
         break;
      case PDI__F_avg_first:
         memcpy(cur, raw, filter_bytes);
         for (k = filter_bytes; k < nk; ++k)
            cur[k] = PDI__BYTECAST(raw[k] + (cur[k-filter_bytes] >> 1));
         break;
      }

      raw += nk;

      // expand decoded bits in cur to dest, also adding an extra alpha channel if desired
      if (depth < 8) {
         pdi_uc scale = (color == 0) ? pdi__depth_scale_table[depth] : 1; // scale grayscale values to 0..255 range
         pdi_uc *in = cur;
         pdi_uc *out = dest;
         pdi_uc inb = 0;
         pdi__uint32 nsmp = x*img_n;

         // expand bits to bytes first
         if (depth == 4) {
            for (i=0; i < nsmp; ++i) {
               if ((i & 1) == 0) inb = *in++;
               *out++ = scale * (inb >> 4);
               inb <<= 4;
            }
         } else if (depth == 2) {
            for (i=0; i < nsmp; ++i) {
               if ((i & 3) == 0) inb = *in++;
               *out++ = scale * (inb >> 6);
               inb <<= 2;
            }
         } else {
            PDI_ASSERT(depth == 1);
            for (i=0; i < nsmp; ++i) {
               if ((i & 7) == 0) inb = *in++;
               *out++ = scale * (inb >> 7);
               inb <<= 1;
            }
         }

         // insert alpha=255 values if desired
         if (img_n != out_n)
            pdi__create_png_alpha_expand8(dest, dest, x, img_n);
      } else if (depth == 8) {
         if (img_n == out_n)
            memcpy(dest, cur, x*img_n);
         else
            pdi__create_png_alpha_expand8(dest, cur, x, img_n);
      } else if (depth == 16) {
         // convert the image data from big-endian to platform-native
         pdi__uint16 *dest16 = (pdi__uint16*)dest;
         pdi__uint32 nsmp = x*img_n;

         if (img_n == out_n) {
            for (i = 0; i < nsmp; ++i, ++dest16, cur += 2)
               *dest16 = (cur[0] << 8) | cur[1];
         } else {
            PDI_ASSERT(img_n+1 == out_n);
            if (img_n == 1) {
               for (i = 0; i < x; ++i, dest16 += 2, cur += 2) {
                  dest16[0] = (cur[0] << 8) | cur[1];
                  dest16[1] = 0xffff;
               }
            } else {
               PDI_ASSERT(img_n == 3);
               for (i = 0; i < x; ++i, dest16 += 4, cur += 6) {
                  dest16[0] = (cur[0] << 8) | cur[1];
                  dest16[1] = (cur[2] << 8) | cur[3];
                  dest16[2] = (cur[4] << 8) | cur[5];
                  dest16[3] = 0xffff;
               }
            }
         }
      }
   }

   PDI_FREE(filter_buf);
   if (!all_ok) return 0;

   return 1;
}

static int pdi__create_png_image(pdi__png *a, pdi_uc *image_data, pdi__uint32 image_data_len, int out_n, int depth, int color, int interlaced)
{
   int bytes = (depth == 16 ? 2 : 1);
   int out_bytes = out_n * bytes;
   pdi_uc *final;
   int p;
   if (!interlaced)
      return pdi__create_png_image_raw(a, image_data, image_data_len, out_n, a->s->img_x, a->s->img_y, depth, color);

   // de-interlacing
   final = (pdi_uc *) pdi__malloc_mad3(a->s->img_x, a->s->img_y, out_bytes, 0);
   if (!final) return pdi__err("outofmem", "Out of memory");
   for (p=0; p < 7; ++p) {
      int xorig[] = { 0,4,0,2,0,1,0 };
      int yorig[] = { 0,0,4,0,2,0,1 };
      int xspc[]  = { 8,8,4,4,2,2,1 };
      int yspc[]  = { 8,8,8,4,4,2,2 };
      int i,j,x,y;
      // pass1_x[4] = 0, pass1_x[5] = 1, pass1_x[12] = 1
      x = (a->s->img_x - xorig[p] + xspc[p]-1) / xspc[p];
      y = (a->s->img_y - yorig[p] + yspc[p]-1) / yspc[p];
      if (x && y) {
         pdi__uint32 img_len = ((((a->s->img_n * x * depth) + 7) >> 3) + 1) * y;
         if (!pdi__create_png_image_raw(a, image_data, image_data_len, out_n, x, y, depth, color)) {
            PDI_FREE(final);
            return 0;
         }
         for (j=0; j < y; ++j) {
            for (i=0; i < x; ++i) {
               int out_y = j*yspc[p]+yorig[p];
               int out_x = i*xspc[p]+xorig[p];
               memcpy(final + out_y*a->s->img_x*out_bytes + out_x*out_bytes,
                      a->out + (j*x+i)*out_bytes, out_bytes);
            }
         }
         PDI_FREE(a->out);
         image_data += img_len;
         image_data_len -= img_len;
      }
   }
   a->out = final;

   return 1;
}

static int pdi__compute_transparency(pdi__png *z, pdi_uc tc[3], int out_n)
{
   pdi__context *s = z->s;
   pdi__uint32 i, pixel_count = s->img_x * s->img_y;
   pdi_uc *p = z->out;

   // compute color-based transparency, assuming we've
   // already got 255 as the alpha value in the output
   PDI_ASSERT(out_n == 2 || out_n == 4);

   if (out_n == 2) {
      for (i=0; i < pixel_count; ++i) {
         p[1] = (p[0] == tc[0] ? 0 : 255);
         p += 2;
      }
   } else {
      for (i=0; i < pixel_count; ++i) {
         if (p[0] == tc[0] && p[1] == tc[1] && p[2] == tc[2])
            p[3] = 0;
         p += 4;
      }
   }
   return 1;
}

static int pdi__compute_transparency16(pdi__png *z, pdi__uint16 tc[3], int out_n)
{
   pdi__context *s = z->s;
   pdi__uint32 i, pixel_count = s->img_x * s->img_y;
   pdi__uint16 *p = (pdi__uint16*) z->out;

   // compute color-based transparency, assuming we've
   // already got 65535 as the alpha value in the output
   PDI_ASSERT(out_n == 2 || out_n == 4);

   if (out_n == 2) {
      for (i = 0; i < pixel_count; ++i) {
         p[1] = (p[0] == tc[0] ? 0 : 65535);
         p += 2;
      }
   } else {
      for (i = 0; i < pixel_count; ++i) {
         if (p[0] == tc[0] && p[1] == tc[1] && p[2] == tc[2])
            p[3] = 0;
         p += 4;
      }
   }
   return 1;
}

static int pdi__expand_png_palette(pdi__png *a, pdi_uc *palette, int len, int pal_img_n)
{
   pdi__uint32 i, pixel_count = a->s->img_x * a->s->img_y;
   pdi_uc *p, *temp_out, *orig = a->out;

   p = (pdi_uc *) pdi__malloc_mad2(pixel_count, pal_img_n, 0);
   if (p == NULL) return pdi__err("outofmem", "Out of memory");

   // between here and free(out) below, exitting would leak
   temp_out = p;

   if (pal_img_n == 3) {
      for (i=0; i < pixel_count; ++i) {
         int n = orig[i]*4;
         p[0] = palette[n  ];
         p[1] = palette[n+1];
         p[2] = palette[n+2];
         p += 3;
      }
   } else {
      for (i=0; i < pixel_count; ++i) {
         int n = orig[i]*4;
         p[0] = palette[n  ];
         p[1] = palette[n+1];
         p[2] = palette[n+2];
         p[3] = palette[n+3];
         p += 4;
      }
   }
   PDI_FREE(a->out);
   a->out = temp_out;

   PDI_NOTUSED(len);

   return 1;
}

static int pdi__unpremultiply_on_load_global = 0;
static int pdi__de_iphone_flag_global = 0;

PDIDEF void pdi_set_unpremultiply_on_load(int flag_true_if_should_unpremultiply)
{
   pdi__unpremultiply_on_load_global = flag_true_if_should_unpremultiply;
}

PDIDEF void pdi_convert_iphone_png_to_rgb(int flag_true_if_should_convert)
{
   pdi__de_iphone_flag_global = flag_true_if_should_convert;
}

#ifndef PDI_THREAD_LOCAL
#define pdi__unpremultiply_on_load  pdi__unpremultiply_on_load_global
#define pdi__de_iphone_flag  pdi__de_iphone_flag_global
#else
static PDI_THREAD_LOCAL int pdi__unpremultiply_on_load_local, pdi__unpremultiply_on_load_set;
static PDI_THREAD_LOCAL int pdi__de_iphone_flag_local, pdi__de_iphone_flag_set;

PDIDEF void pdi_set_unpremultiply_on_load_thread(int flag_true_if_should_unpremultiply)
{
   pdi__unpremultiply_on_load_local = flag_true_if_should_unpremultiply;
   pdi__unpremultiply_on_load_set = 1;
}

PDIDEF void pdi_convert_iphone_png_to_rgb_thread(int flag_true_if_should_convert)
{
   pdi__de_iphone_flag_local = flag_true_if_should_convert;
   pdi__de_iphone_flag_set = 1;
}

#define pdi__unpremultiply_on_load  (pdi__unpremultiply_on_load_set           \
                                       ? pdi__unpremultiply_on_load_local      \
                                       : pdi__unpremultiply_on_load_global)
#define pdi__de_iphone_flag  (pdi__de_iphone_flag_set                         \
                                ? pdi__de_iphone_flag_local                    \
                                : pdi__de_iphone_flag_global)
#endif // PDI_THREAD_LOCAL

static void pdi__de_iphone(pdi__png *z)
{
   pdi__context *s = z->s;
   pdi__uint32 i, pixel_count = s->img_x * s->img_y;
   pdi_uc *p = z->out;

   if (s->img_out_n == 3) {  // convert bgr to rgb
      for (i=0; i < pixel_count; ++i) {
         pdi_uc t = p[0];
         p[0] = p[2];
         p[2] = t;
         p += 3;
      }
   } else {
      PDI_ASSERT(s->img_out_n == 4);
      if (pdi__unpremultiply_on_load) {
         // convert bgr to rgb and unpremultiply
         for (i=0; i < pixel_count; ++i) {
            pdi_uc a = p[3];
            pdi_uc t = p[0];
            if (a) {
               pdi_uc half = a / 2;
               p[0] = (p[2] * 255 + half) / a;
               p[1] = (p[1] * 255 + half) / a;
               p[2] = ( t   * 255 + half) / a;
            } else {
               p[0] = p[2];
               p[2] = t;
            }
            p += 4;
         }
      } else {
         // convert bgr to rgb
         for (i=0; i < pixel_count; ++i) {
            pdi_uc t = p[0];
            p[0] = p[2];
            p[2] = t;
            p += 4;
         }
      }
   }
}

#define PDI__PNG_TYPE(a,b,c,d)  (((unsigned) (a) << 24) + ((unsigned) (b) << 16) + ((unsigned) (c) << 8) + (unsigned) (d))

static int pdi__parse_png_file(pdi__png *z, int scan, int req_comp)
{
   pdi_uc palette[1024], pal_img_n=0;
   pdi_uc has_trans=0, tc[3]={0};
   pdi__uint16 tc16[3];
   pdi__uint32 ioff=0, idata_limit=0, i, pal_len=0;
   int first=1,k,interlace=0, color=0, is_iphone=0;
   pdi__context *s = z->s;

   z->expanded = NULL;
   z->idata = NULL;
   z->out = NULL;

   if (!pdi__check_png_header(s)) return 0;

   if (scan == PDI__SCAN_type) return 1;

   for (;;) {
      pdi__pngchunk c = pdi__get_chunk_header(s);
      switch (c.type) {
         case PDI__PNG_TYPE('C','g','B','I'):
            is_iphone = 1;
            pdi__skip(s, c.length);
            break;
         case PDI__PNG_TYPE('I','H','D','R'): {
            int comp,filter;
            if (!first) return pdi__err("multiple IHDR","Corrupt PNG");
            first = 0;
            if (c.length != 13) return pdi__err("bad IHDR len","Corrupt PNG");
            s->img_x = pdi__get32be(s);
            s->img_y = pdi__get32be(s);
            if (s->img_y > PDI_MAX_DIMENSIONS) return pdi__err("too large","Very large image (corrupt?)");
            if (s->img_x > PDI_MAX_DIMENSIONS) return pdi__err("too large","Very large image (corrupt?)");
            z->depth = pdi__get8(s);  if (z->depth != 1 && z->depth != 2 && z->depth != 4 && z->depth != 8 && z->depth != 16)  return pdi__err("1/2/4/8/16-bit only","PNG not supported: 1/2/4/8/16-bit only");
            color = pdi__get8(s);  if (color > 6)         return pdi__err("bad ctype","Corrupt PNG");
            if (color == 3 && z->depth == 16)                  return pdi__err("bad ctype","Corrupt PNG");
            if (color == 3) pal_img_n = 3; else if (color & 1) return pdi__err("bad ctype","Corrupt PNG");
            comp  = pdi__get8(s);  if (comp) return pdi__err("bad comp method","Corrupt PNG");
            filter= pdi__get8(s);  if (filter) return pdi__err("bad filter method","Corrupt PNG");
            interlace = pdi__get8(s); if (interlace>1) return pdi__err("bad interlace method","Corrupt PNG");
            if (!s->img_x || !s->img_y) return pdi__err("0-pixel image","Corrupt PNG");
            if (!pal_img_n) {
               s->img_n = (color & 2 ? 3 : 1) + (color & 4 ? 1 : 0);
               if ((1 << 30) / s->img_x / s->img_n < s->img_y) return pdi__err("too large", "Image too large to decode");
            } else {
               // if paletted, then pal_n is our final components, and
               // img_n is # components to decompress/filter.
               s->img_n = 1;
               if ((1 << 30) / s->img_x / 4 < s->img_y) return pdi__err("too large","Corrupt PNG");
            }
            // even with SCAN_header, have to scan to see if we have a tRNS
            break;
         }

         case PDI__PNG_TYPE('P','L','T','E'):  {
            if (first) return pdi__err("first not IHDR", "Corrupt PNG");
            if (c.length > 256*3) return pdi__err("invalid PLTE","Corrupt PNG");
            pal_len = c.length / 3;
            if (pal_len * 3 != c.length) return pdi__err("invalid PLTE","Corrupt PNG");
            for (i=0; i < pal_len; ++i) {
               palette[i*4+0] = pdi__get8(s);
               palette[i*4+1] = pdi__get8(s);
               palette[i*4+2] = pdi__get8(s);
               palette[i*4+3] = 255;
            }
            break;
         }

         case PDI__PNG_TYPE('t','R','N','S'): {
            if (first) return pdi__err("first not IHDR", "Corrupt PNG");
            if (z->idata) return pdi__err("tRNS after IDAT","Corrupt PNG");
            if (pal_img_n) {
               if (scan == PDI__SCAN_header) { s->img_n = 4; return 1; }
               if (pal_len == 0) return pdi__err("tRNS before PLTE","Corrupt PNG");
               if (c.length > pal_len) return pdi__err("bad tRNS len","Corrupt PNG");
               pal_img_n = 4;
               for (i=0; i < c.length; ++i)
                  palette[i*4+3] = pdi__get8(s);
            } else {
               if (!(s->img_n & 1)) return pdi__err("tRNS with alpha","Corrupt PNG");
               if (c.length != (pdi__uint32) s->img_n*2) return pdi__err("bad tRNS len","Corrupt PNG");
               has_trans = 1;
               // non-paletted with tRNS = constant alpha. if header-scanning, we can stop now.
               if (scan == PDI__SCAN_header) { ++s->img_n; return 1; }
               if (z->depth == 16) {
                  for (k = 0; k < s->img_n && k < 3; ++k) // extra loop test to suppress false GCC warning
                     tc16[k] = (pdi__uint16)pdi__get16be(s); // copy the values as-is
               } else {
                  for (k = 0; k < s->img_n && k < 3; ++k)
                     tc[k] = (pdi_uc)(pdi__get16be(s) & 255) * pdi__depth_scale_table[z->depth]; // non 8-bit images will be larger
               }
            }
            break;
         }

         case PDI__PNG_TYPE('I','D','A','T'): {
            if (first) return pdi__err("first not IHDR", "Corrupt PNG");
            if (pal_img_n && !pal_len) return pdi__err("no PLTE","Corrupt PNG");
            if (scan == PDI__SCAN_header) {
               // header scan definitely stops at first IDAT
               if (pal_img_n)
                  s->img_n = pal_img_n;
               return 1;
            }
            if (c.length > (1u << 30)) return pdi__err("IDAT size limit", "IDAT section larger than 2^30 bytes");
            if ((int)(ioff + c.length) < (int)ioff) return 0;
            if (ioff + c.length > idata_limit) {
               pdi__uint32 idata_limit_old = idata_limit;
               pdi_uc *p;
               if (idata_limit == 0) idata_limit = c.length > 4096 ? c.length : 4096;
               while (ioff + c.length > idata_limit)
                  idata_limit *= 2;
               PDI_NOTUSED(idata_limit_old);
               p = (pdi_uc *) PDI_REALLOC_SIZED(z->idata, idata_limit_old, idata_limit); if (p == NULL) return pdi__err("outofmem", "Out of memory");
               z->idata = p;
            }
            if (!pdi__getn(s, z->idata+ioff,c.length)) return pdi__err("outofdata","Corrupt PNG");
            ioff += c.length;
            break;
         }

         case PDI__PNG_TYPE('I','E','N','D'): {
            pdi__uint32 raw_len, bpl;
            if (first) return pdi__err("first not IHDR", "Corrupt PNG");
            if (scan != PDI__SCAN_load) return 1;
            if (z->idata == NULL) return pdi__err("no IDAT","Corrupt PNG");
            // initial guess for decoded data size to avoid unnecessary reallocs
            bpl = (s->img_x * z->depth + 7) / 8; // bytes per line, per component
            raw_len = bpl * s->img_y * s->img_n /* pixels */ + s->img_y /* filter mode per row */;
            z->expanded = (pdi_uc *) pdi_zlib_decode_malloc_guesssize_headerflag((char *) z->idata, ioff, raw_len, (int *) &raw_len, !is_iphone);
            if (z->expanded == NULL) return 0; // zlib should set error
            PDI_FREE(z->idata); z->idata = NULL;
            if ((req_comp == s->img_n+1 && req_comp != 3 && !pal_img_n) || has_trans)
               s->img_out_n = s->img_n+1;
            else
               s->img_out_n = s->img_n;
            if (!pdi__create_png_image(z, z->expanded, raw_len, s->img_out_n, z->depth, color, interlace)) return 0;
            if (has_trans) {
               if (z->depth == 16) {
                  if (!pdi__compute_transparency16(z, tc16, s->img_out_n)) return 0;
               } else {
                  if (!pdi__compute_transparency(z, tc, s->img_out_n)) return 0;
               }
            }
            if (is_iphone && pdi__de_iphone_flag && s->img_out_n > 2)
               pdi__de_iphone(z);
            if (pal_img_n) {
               // pal_img_n == 3 or 4
               s->img_n = pal_img_n; // record the actual colors we had
               s->img_out_n = pal_img_n;
               if (req_comp >= 3) s->img_out_n = req_comp;
               if (!pdi__expand_png_palette(z, palette, pal_len, s->img_out_n))
                  return 0;
            } else if (has_trans) {
               // non-paletted image with tRNS -> source image has (constant) alpha
               ++s->img_n;
            }
            PDI_FREE(z->expanded); z->expanded = NULL;
            // end of PNG chunk, read and skip CRC
            pdi__get32be(s);
            return 1;
         }

         default:
            // if critical, fail
            if (first) return pdi__err("first not IHDR", "Corrupt PNG");
            if ((c.type & (1 << 29)) == 0) {
               #ifndef PDI_NO_FAILURE_STRINGS
               // not threadsafe
               static char invalid_chunk[] = "XXXX PNG chunk not known";
               invalid_chunk[0] = PDI__BYTECAST(c.type >> 24);
               invalid_chunk[1] = PDI__BYTECAST(c.type >> 16);
               invalid_chunk[2] = PDI__BYTECAST(c.type >>  8);
               invalid_chunk[3] = PDI__BYTECAST(c.type >>  0);
               #endif
               return pdi__err(invalid_chunk, "PNG not supported: unknown PNG chunk type");
            }
            pdi__skip(s, c.length);
            break;
      }
      // end of PNG chunk, read and skip CRC
      pdi__get32be(s);
   }
}

static void *pdi__do_png(pdi__png *p, int *x, int *y, int *n, int req_comp, pdi__result_info *ri)
{
   void *result=NULL;
   if (req_comp < 0 || req_comp > 4) return pdi__errpuc("bad req_comp", "Internal error");
   if (pdi__parse_png_file(p, PDI__SCAN_load, req_comp)) {
      if (p->depth <= 8)
         ri->bits_per_channel = 8;
      else if (p->depth == 16)
         ri->bits_per_channel = 16;
      else
         return pdi__errpuc("bad bits_per_channel", "PNG not supported: unsupported color depth");
      result = p->out;
      p->out = NULL;
      if (req_comp && req_comp != p->s->img_out_n) {
         if (ri->bits_per_channel == 8)
            result = pdi__convert_format((unsigned char *) result, p->s->img_out_n, req_comp, p->s->img_x, p->s->img_y);
         else
            result = pdi__convert_format16((pdi__uint16 *) result, p->s->img_out_n, req_comp, p->s->img_x, p->s->img_y);
         p->s->img_out_n = req_comp;
         if (result == NULL) return result;
      }
      *x = p->s->img_x;
      *y = p->s->img_y;
      if (n) *n = p->s->img_n;
   }
   PDI_FREE(p->out);      p->out      = NULL;
   PDI_FREE(p->expanded); p->expanded = NULL;
   PDI_FREE(p->idata);    p->idata    = NULL;

   return result;
}

static void *pdi__png_load(pdi__context *s, int *x, int *y, int *comp, int req_comp, pdi__result_info *ri)
{
   pdi__png p;
   p.s = s;
   return pdi__do_png(&p, x,y,comp,req_comp, ri);
}

static int pdi__png_test(pdi__context *s)
{
   int r;
   r = pdi__check_png_header(s);
   pdi__rewind(s);
   return r;
}

static int pdi__png_info_raw(pdi__png *p, int *x, int *y, int *comp)
{
   if (!pdi__parse_png_file(p, PDI__SCAN_header, 0)) {
      pdi__rewind( p->s );
      return 0;
   }
   if (x) *x = p->s->img_x;
   if (y) *y = p->s->img_y;
   if (comp) *comp = p->s->img_n;
   return 1;
}

static int pdi__png_info(pdi__context *s, int *x, int *y, int *comp)
{
   pdi__png p;
   p.s = s;
   return pdi__png_info_raw(&p, x, y, comp);
}

static int pdi__png_is16(pdi__context *s)
{
   pdi__png p;
   p.s = s;
   if (!pdi__png_info_raw(&p, NULL, NULL, NULL))
	   return 0;
   if (p.depth != 16) {
      pdi__rewind(p.s);
      return 0;
   }
   return 1;
}
#endif

// Microsoft/Windows BMP image

#ifndef PDI_NO_BMP
static int pdi__bmp_test_raw(pdi__context *s)
{
   int r;
   int sz;
   if (pdi__get8(s) != 'B') return 0;
   if (pdi__get8(s) != 'M') return 0;
   pdi__get32le(s); // discard filesize
   pdi__get16le(s); // discard reserved
   pdi__get16le(s); // discard reserved
   pdi__get32le(s); // discard data offset
   sz = pdi__get32le(s);
   r = (sz == 12 || sz == 40 || sz == 56 || sz == 108 || sz == 124);
   return r;
}

static int pdi__bmp_test(pdi__context *s)
{
   int r = pdi__bmp_test_raw(s);
   pdi__rewind(s);
   return r;
}


// returns 0..31 for the highest set bit
static int pdi__high_bit(unsigned int z)
{
   int n=0;
   if (z == 0) return -1;
   if (z >= 0x10000) { n += 16; z >>= 16; }
   if (z >= 0x00100) { n +=  8; z >>=  8; }
   if (z >= 0x00010) { n +=  4; z >>=  4; }
   if (z >= 0x00004) { n +=  2; z >>=  2; }
   if (z >= 0x00002) { n +=  1;/* >>=  1;*/ }
   return n;
}

static int pdi__bitcount(unsigned int a)
{
   a = (a & 0x55555555) + ((a >>  1) & 0x55555555); // max 2
   a = (a & 0x33333333) + ((a >>  2) & 0x33333333); // max 4
   a = (a + (a >> 4)) & 0x0f0f0f0f; // max 8 per 4, now 8 bits
   a = (a + (a >> 8)); // max 16 per 8 bits
   a = (a + (a >> 16)); // max 32 per 8 bits
   return a & 0xff;
}

// extract an arbitrarily-aligned N-bit value (N=bits)
// from v, and then make it 8-bits long and fractionally
// extend it to full full range.
static int pdi__shiftsigned(unsigned int v, int shift, int bits)
{
   static unsigned int mul_table[9] = {
      0,
      0xff/*0b11111111*/, 0x55/*0b01010101*/, 0x49/*0b01001001*/, 0x11/*0b00010001*/,
      0x21/*0b00100001*/, 0x41/*0b01000001*/, 0x81/*0b10000001*/, 0x01/*0b00000001*/,
   };
   static unsigned int shift_table[9] = {
      0, 0,0,1,0,2,4,6,0,
   };
   if (shift < 0)
      v <<= -shift;
   else
      v >>= shift;
   PDI_ASSERT(v < 256);
   v >>= (8-bits);
   PDI_ASSERT(bits >= 0 && bits <= 8);
   return (int) ((unsigned) v * mul_table[bits]) >> shift_table[bits];
}

typedef struct
{
   int bpp, offset, hsz;
   unsigned int mr,mg,mb,ma, all_a;
   int extra_read;
} pdi__bmp_data;

static int pdi__bmp_set_mask_defaults(pdi__bmp_data *info, int compress)
{
   // BI_BITFIELDS specifies masks explicitly, don't override
   if (compress == 3)
      return 1;

   if (compress == 0) {
      if (info->bpp == 16) {
         info->mr = 31u << 10;
         info->mg = 31u <<  5;
         info->mb = 31u <<  0;
      } else if (info->bpp == 32) {
         info->mr = 0xffu << 16;
         info->mg = 0xffu <<  8;
         info->mb = 0xffu <<  0;
         info->ma = 0xffu << 24;
         info->all_a = 0; // if all_a is 0 at end, then we loaded alpha channel but it was all 0
      } else {
         // otherwise, use defaults, which is all-0
         info->mr = info->mg = info->mb = info->ma = 0;
      }
      return 1;
   }
   return 0; // error
}

static void *pdi__bmp_parse_header(pdi__context *s, pdi__bmp_data *info)
{
   int hsz;
   if (pdi__get8(s) != 'B' || pdi__get8(s) != 'M') return pdi__errpuc("not BMP", "Corrupt BMP");
   pdi__get32le(s); // discard filesize
   pdi__get16le(s); // discard reserved
   pdi__get16le(s); // discard reserved
   info->offset = pdi__get32le(s);
   info->hsz = hsz = pdi__get32le(s);
   info->mr = info->mg = info->mb = info->ma = 0;
   info->extra_read = 14;

   if (info->offset < 0) return pdi__errpuc("bad BMP", "bad BMP");

   if (hsz != 12 && hsz != 40 && hsz != 56 && hsz != 108 && hsz != 124) return pdi__errpuc("unknown BMP", "BMP type not supported: unknown");
   if (hsz == 12) {
      s->img_x = pdi__get16le(s);
      s->img_y = pdi__get16le(s);
   } else {
      s->img_x = pdi__get32le(s);
      s->img_y = pdi__get32le(s);
   }
   if (pdi__get16le(s) != 1) return pdi__errpuc("bad BMP", "bad BMP");
   info->bpp = pdi__get16le(s);
   if (hsz != 12) {
      int compress = pdi__get32le(s);
      if (compress == 1 || compress == 2) return pdi__errpuc("BMP RLE", "BMP type not supported: RLE");
      if (compress >= 4) return pdi__errpuc("BMP JPEG/PNG", "BMP type not supported: unsupported compression"); // this includes PNG/JPEG modes
      if (compress == 3 && info->bpp != 16 && info->bpp != 32) return pdi__errpuc("bad BMP", "bad BMP"); // bitfields requires 16 or 32 bits/pixel
      pdi__get32le(s); // discard sizeof
      pdi__get32le(s); // discard hres
      pdi__get32le(s); // discard vres
      pdi__get32le(s); // discard colorsused
      pdi__get32le(s); // discard max important
      if (hsz == 40 || hsz == 56) {
         if (hsz == 56) {
            pdi__get32le(s);
            pdi__get32le(s);
            pdi__get32le(s);
            pdi__get32le(s);
         }
         if (info->bpp == 16 || info->bpp == 32) {
            if (compress == 0) {
               pdi__bmp_set_mask_defaults(info, compress);
            } else if (compress == 3) {
               info->mr = pdi__get32le(s);
               info->mg = pdi__get32le(s);
               info->mb = pdi__get32le(s);
               info->extra_read += 12;
               // not documented, but generated by photoshop and handled by mspaint
               if (info->mr == info->mg && info->mg == info->mb) {
                  // ?!?!?
                  return pdi__errpuc("bad BMP", "bad BMP");
               }
            } else
               return pdi__errpuc("bad BMP", "bad BMP");
         }
      } else {
         // V4/V5 header
         int i;
         if (hsz != 108 && hsz != 124)
            return pdi__errpuc("bad BMP", "bad BMP");
         info->mr = pdi__get32le(s);
         info->mg = pdi__get32le(s);
         info->mb = pdi__get32le(s);
         info->ma = pdi__get32le(s);
         if (compress != 3) // override mr/mg/mb unless in BI_BITFIELDS mode, as per docs
            pdi__bmp_set_mask_defaults(info, compress);
         pdi__get32le(s); // discard color space
         for (i=0; i < 12; ++i)
            pdi__get32le(s); // discard color space parameters
         if (hsz == 124) {
            pdi__get32le(s); // discard rendering intent
            pdi__get32le(s); // discard offset of profile data
            pdi__get32le(s); // discard size of profile data
            pdi__get32le(s); // discard reserved
         }
      }
   }
   return (void *) 1;
}


static void *pdi__bmp_load(pdi__context *s, int *x, int *y, int *comp, int req_comp, pdi__result_info *ri)
{
   pdi_uc *out;
   unsigned int mr=0,mg=0,mb=0,ma=0, all_a;
   pdi_uc pal[256][4];
   int psize=0,i,j,width;
   int flip_vertically, pad, target;
   pdi__bmp_data info;
   PDI_NOTUSED(ri);

   info.all_a = 255;
   if (pdi__bmp_parse_header(s, &info) == NULL)
      return NULL; // error code already set

   flip_vertically = ((int) s->img_y) > 0;
   s->img_y = abs((int) s->img_y);

   if (s->img_y > PDI_MAX_DIMENSIONS) return pdi__errpuc("too large","Very large image (corrupt?)");
   if (s->img_x > PDI_MAX_DIMENSIONS) return pdi__errpuc("too large","Very large image (corrupt?)");

   mr = info.mr;
   mg = info.mg;
   mb = info.mb;
   ma = info.ma;
   all_a = info.all_a;

   if (info.hsz == 12) {
      if (info.bpp < 24)
         psize = (info.offset - info.extra_read - 24) / 3;
   } else {
      if (info.bpp < 16)
         psize = (info.offset - info.extra_read - info.hsz) >> 2;
   }
   if (psize == 0) {
      // accept some number of extra bytes after the header, but if the offset points either to before
      // the header ends or implies a large amount of extra data, reject the file as malformed
      int bytes_read_so_far = s->callback_already_read + (int)(s->img_buffer - s->img_buffer_original);
      int header_limit = 1024; // max we actually read is below 256 bytes currently.
      int extra_data_limit = 256*4; // what ordinarily goes here is a palette; 256 entries*4 bytes is its max size.
      if (bytes_read_so_far <= 0 || bytes_read_so_far > header_limit) {
         return pdi__errpuc("bad header", "Corrupt BMP");
      }
      // we established that bytes_read_so_far is positive and sensible.
      // the first half of this test rejects offsets that are either too small positives, or
      // negative, and guarantees that info.offset >= bytes_read_so_far > 0. this in turn
      // ensures the number computed in the second half of the test can't overflow.
      if (info.offset < bytes_read_so_far || info.offset - bytes_read_so_far > extra_data_limit) {
         return pdi__errpuc("bad offset", "Corrupt BMP");
      } else {
         pdi__skip(s, info.offset - bytes_read_so_far);
      }
   }

   if (info.bpp == 24 && ma == 0xff000000)
      s->img_n = 3;
   else
      s->img_n = ma ? 4 : 3;
   if (req_comp && req_comp >= 3) // we can directly decode 3 or 4
      target = req_comp;
   else
      target = s->img_n; // if they want monochrome, we'll post-convert

   // sanity-check size
   if (!pdi__mad3sizes_valid(target, s->img_x, s->img_y, 0))
      return pdi__errpuc("too large", "Corrupt BMP");

   out = (pdi_uc *) pdi__malloc_mad3(target, s->img_x, s->img_y, 0);
   if (!out) return pdi__errpuc("outofmem", "Out of memory");
   if (info.bpp < 16) {
      int z=0;
      if (psize == 0 || psize > 256) { PDI_FREE(out); return pdi__errpuc("invalid", "Corrupt BMP"); }
      for (i=0; i < psize; ++i) {
         pal[i][2] = pdi__get8(s);
         pal[i][1] = pdi__get8(s);
         pal[i][0] = pdi__get8(s);
         if (info.hsz != 12) pdi__get8(s);
         pal[i][3] = 255;
      }
      pdi__skip(s, info.offset - info.extra_read - info.hsz - psize * (info.hsz == 12 ? 3 : 4));
      if (info.bpp == 1) width = (s->img_x + 7) >> 3;
      else if (info.bpp == 4) width = (s->img_x + 1) >> 1;
      else if (info.bpp == 8) width = s->img_x;
      else { PDI_FREE(out); return pdi__errpuc("bad bpp", "Corrupt BMP"); }
      pad = (-width)&3;
      if (info.bpp == 1) {
         for (j=0; j < (int) s->img_y; ++j) {
            int bit_offset = 7, v = pdi__get8(s);
            for (i=0; i < (int) s->img_x; ++i) {
               int color = (v>>bit_offset)&0x1;
               out[z++] = pal[color][0];
               out[z++] = pal[color][1];
               out[z++] = pal[color][2];
               if (target == 4) out[z++] = 255;
               if (i+1 == (int) s->img_x) break;
               if((--bit_offset) < 0) {
                  bit_offset = 7;
                  v = pdi__get8(s);
               }
            }
            pdi__skip(s, pad);
         }
      } else {
         for (j=0; j < (int) s->img_y; ++j) {
            for (i=0; i < (int) s->img_x; i += 2) {
               int v=pdi__get8(s),v2=0;
               if (info.bpp == 4) {
                  v2 = v & 15;
                  v >>= 4;
               }
               out[z++] = pal[v][0];
               out[z++] = pal[v][1];
               out[z++] = pal[v][2];
               if (target == 4) out[z++] = 255;
               if (i+1 == (int) s->img_x) break;
               v = (info.bpp == 8) ? pdi__get8(s) : v2;
               out[z++] = pal[v][0];
               out[z++] = pal[v][1];
               out[z++] = pal[v][2];
               if (target == 4) out[z++] = 255;
            }
            pdi__skip(s, pad);
         }
      }
   } else {
      int rshift=0,gshift=0,bshift=0,ashift=0,rcount=0,gcount=0,bcount=0,acount=0;
      int z = 0;
      int easy=0;
      pdi__skip(s, info.offset - info.extra_read - info.hsz);
      if (info.bpp == 24) width = 3 * s->img_x;
      else if (info.bpp == 16) width = 2*s->img_x;
      else /* bpp = 32 and pad = 0 */ width=0;
      pad = (-width) & 3;
      if (info.bpp == 24) {
         easy = 1;
      } else if (info.bpp == 32) {
         if (mb == 0xff && mg == 0xff00 && mr == 0x00ff0000 && ma == 0xff000000)
            easy = 2;
      }
      if (!easy) {
         if (!mr || !mg || !mb) { PDI_FREE(out); return pdi__errpuc("bad masks", "Corrupt BMP"); }
         // right shift amt to put high bit in position #7
         rshift = pdi__high_bit(mr)-7; rcount = pdi__bitcount(mr);
         gshift = pdi__high_bit(mg)-7; gcount = pdi__bitcount(mg);
         bshift = pdi__high_bit(mb)-7; bcount = pdi__bitcount(mb);
         ashift = pdi__high_bit(ma)-7; acount = pdi__bitcount(ma);
         if (rcount > 8 || gcount > 8 || bcount > 8 || acount > 8) { PDI_FREE(out); return pdi__errpuc("bad masks", "Corrupt BMP"); }
      }
      for (j=0; j < (int) s->img_y; ++j) {
         if (easy) {
            for (i=0; i < (int) s->img_x; ++i) {
               unsigned char a;
               out[z+2] = pdi__get8(s);
               out[z+1] = pdi__get8(s);
               out[z+0] = pdi__get8(s);
               z += 3;
               a = (easy == 2 ? pdi__get8(s) : 255);
               all_a |= a;
               if (target == 4) out[z++] = a;
            }
         } else {
            int bpp = info.bpp;
            for (i=0; i < (int) s->img_x; ++i) {
               pdi__uint32 v = (bpp == 16 ? (pdi__uint32) pdi__get16le(s) : pdi__get32le(s));
               unsigned int a;
               out[z++] = PDI__BYTECAST(pdi__shiftsigned(v & mr, rshift, rcount));
               out[z++] = PDI__BYTECAST(pdi__shiftsigned(v & mg, gshift, gcount));
               out[z++] = PDI__BYTECAST(pdi__shiftsigned(v & mb, bshift, bcount));
               a = (ma ? pdi__shiftsigned(v & ma, ashift, acount) : 255);
               all_a |= a;
               if (target == 4) out[z++] = PDI__BYTECAST(a);
            }
         }
         pdi__skip(s, pad);
      }
   }

   // if alpha channel is all 0s, replace with all 255s
   if (target == 4 && all_a == 0)
      for (i=4*s->img_x*s->img_y-1; i >= 0; i -= 4)
         out[i] = 255;

   if (flip_vertically) {
      pdi_uc t;
      for (j=0; j < (int) s->img_y>>1; ++j) {
         pdi_uc *p1 = out +      j     *s->img_x*target;
         pdi_uc *p2 = out + (s->img_y-1-j)*s->img_x*target;
         for (i=0; i < (int) s->img_x*target; ++i) {
            t = p1[i]; p1[i] = p2[i]; p2[i] = t;
         }
      }
   }

   if (req_comp && req_comp != target) {
      out = pdi__convert_format(out, target, req_comp, s->img_x, s->img_y);
      if (out == NULL) return out; // pdi__convert_format frees input on failure
   }

   *x = s->img_x;
   *y = s->img_y;
   if (comp) *comp = s->img_n;
   return out;
}
#endif

// Targa Truevision - TGA
// by Jonathan Dummer
#ifndef PDI_NO_TGA
// returns PDI_rgb or whatever, 0 on error
static int pdi__tga_get_comp(int bits_per_pixel, int is_grey, int* is_rgb16)
{
   // only RGB or RGBA (incl. 16bit) or grey allowed
   if (is_rgb16) *is_rgb16 = 0;
   switch(bits_per_pixel) {
      case 8:  return PDI_grey;
      case 16: if(is_grey) return PDI_grey_alpha;
               // fallthrough
      case 15: if(is_rgb16) *is_rgb16 = 1;
               return PDI_rgb;
      case 24: // fallthrough
      case 32: return bits_per_pixel/8;
      default: return 0;
   }
}

static int pdi__tga_info(pdi__context *s, int *x, int *y, int *comp)
{
    int tga_w, tga_h, tga_comp, tga_image_type, tga_bits_per_pixel, tga_colormap_bpp;
    int sz, tga_colormap_type;
    pdi__get8(s);                   // discard Offset
    tga_colormap_type = pdi__get8(s); // colormap type
    if( tga_colormap_type > 1 ) {
        pdi__rewind(s);
        return 0;      // only RGB or indexed allowed
    }
    tga_image_type = pdi__get8(s); // image type
    if ( tga_colormap_type == 1 ) { // colormapped (paletted) image
        if (tga_image_type != 1 && tga_image_type != 9) {
            pdi__rewind(s);
            return 0;
        }
        pdi__skip(s,4);       // skip index of first colormap entry and number of entries
        sz = pdi__get8(s);    //   check bits per palette color entry
        if ( (sz != 8) && (sz != 15) && (sz != 16) && (sz != 24) && (sz != 32) ) {
            pdi__rewind(s);
            return 0;
        }
        pdi__skip(s,4);       // skip image x and y origin
        tga_colormap_bpp = sz;
    } else { // "normal" image w/o colormap - only RGB or grey allowed, +/- RLE
        if ( (tga_image_type != 2) && (tga_image_type != 3) && (tga_image_type != 10) && (tga_image_type != 11) ) {
            pdi__rewind(s);
            return 0; // only RGB or grey allowed, +/- RLE
        }
        pdi__skip(s,9); // skip colormap specification and image x/y origin
        tga_colormap_bpp = 0;
    }
    tga_w = pdi__get16le(s);
    if( tga_w < 1 ) {
        pdi__rewind(s);
        return 0;   // test width
    }
    tga_h = pdi__get16le(s);
    if( tga_h < 1 ) {
        pdi__rewind(s);
        return 0;   // test height
    }
    tga_bits_per_pixel = pdi__get8(s); // bits per pixel
    pdi__get8(s); // ignore alpha bits
    if (tga_colormap_bpp != 0) {
        if((tga_bits_per_pixel != 8) && (tga_bits_per_pixel != 16)) {
            // when using a colormap, tga_bits_per_pixel is the size of the indexes
            // I don't think anything but 8 or 16bit indexes makes sense
            pdi__rewind(s);
            return 0;
        }
        tga_comp = pdi__tga_get_comp(tga_colormap_bpp, 0, NULL);
    } else {
        tga_comp = pdi__tga_get_comp(tga_bits_per_pixel, (tga_image_type == 3) || (tga_image_type == 11), NULL);
    }
    if(!tga_comp) {
      pdi__rewind(s);
      return 0;
    }
    if (x) *x = tga_w;
    if (y) *y = tga_h;
    if (comp) *comp = tga_comp;
    return 1;                   // seems to have passed everything
}

static int pdi__tga_test(pdi__context *s)
{
   int res = 0;
   int sz, tga_color_type;
   pdi__get8(s);      //   discard Offset
   tga_color_type = pdi__get8(s);   //   color type
   if ( tga_color_type > 1 ) goto errorEnd;   //   only RGB or indexed allowed
   sz = pdi__get8(s);   //   image type
   if ( tga_color_type == 1 ) { // colormapped (paletted) image
      if (sz != 1 && sz != 9) goto errorEnd; // colortype 1 demands image type 1 or 9
      pdi__skip(s,4);       // skip index of first colormap entry and number of entries
      sz = pdi__get8(s);    //   check bits per palette color entry
      if ( (sz != 8) && (sz != 15) && (sz != 16) && (sz != 24) && (sz != 32) ) goto errorEnd;
      pdi__skip(s,4);       // skip image x and y origin
   } else { // "normal" image w/o colormap
      if ( (sz != 2) && (sz != 3) && (sz != 10) && (sz != 11) ) goto errorEnd; // only RGB or grey allowed, +/- RLE
      pdi__skip(s,9); // skip colormap specification and image x/y origin
   }
   if ( pdi__get16le(s) < 1 ) goto errorEnd;      //   test width
   if ( pdi__get16le(s) < 1 ) goto errorEnd;      //   test height
   sz = pdi__get8(s);   //   bits per pixel
   if ( (tga_color_type == 1) && (sz != 8) && (sz != 16) ) goto errorEnd; // for colormapped images, bpp is size of an index
   if ( (sz != 8) && (sz != 15) && (sz != 16) && (sz != 24) && (sz != 32) ) goto errorEnd;

   res = 1; // if we got this far, everything's good and we can return 1 instead of 0

errorEnd:
   pdi__rewind(s);
   return res;
}

// read 16bit value and convert to 24bit RGB
static void pdi__tga_read_rgb16(pdi__context *s, pdi_uc* out)
{
   pdi__uint16 px = (pdi__uint16)pdi__get16le(s);
   pdi__uint16 fiveBitMask = 31;
   // we have 3 channels with 5bits each
   int r = (px >> 10) & fiveBitMask;
   int g = (px >> 5) & fiveBitMask;
   int b = px & fiveBitMask;
   // Note that this saves the data in RGB(A) order, so it doesn't need to be swapped later
   out[0] = (pdi_uc)((r * 255)/31);
   out[1] = (pdi_uc)((g * 255)/31);
   out[2] = (pdi_uc)((b * 255)/31);

   // some people claim that the most significant bit might be used for alpha
   // (possibly if an alpha-bit is set in the "image descriptor byte")
   // but that only made 16bit test images completely translucent..
   // so let's treat all 15 and 16bit TGAs as RGB with no alpha.
}

static void *pdi__tga_load(pdi__context *s, int *x, int *y, int *comp, int req_comp, pdi__result_info *ri)
{
   //   read in the TGA header stuff
   int tga_offset = pdi__get8(s);
   int tga_indexed = pdi__get8(s);
   int tga_image_type = pdi__get8(s);
   int tga_is_RLE = 0;
   int tga_palette_start = pdi__get16le(s);
   int tga_palette_len = pdi__get16le(s);
   int tga_palette_bits = pdi__get8(s);
   int tga_x_origin = pdi__get16le(s);
   int tga_y_origin = pdi__get16le(s);
   int tga_width = pdi__get16le(s);
   int tga_height = pdi__get16le(s);
   int tga_bits_per_pixel = pdi__get8(s);
   int tga_comp, tga_rgb16=0;
   int tga_inverted = pdi__get8(s);
   // int tga_alpha_bits = tga_inverted & 15; // the 4 lowest bits - unused (useless?)
   //   image data
   unsigned char *tga_data;
   unsigned char *tga_palette = NULL;
   int i, j;
   unsigned char raw_data[4] = {0};
   int RLE_count = 0;
   int RLE_repeating = 0;
   int read_next_pixel = 1;
   PDI_NOTUSED(ri);
   PDI_NOTUSED(tga_x_origin); // @TODO
   PDI_NOTUSED(tga_y_origin); // @TODO

   if (tga_height > PDI_MAX_DIMENSIONS) return pdi__errpuc("too large","Very large image (corrupt?)");
   if (tga_width > PDI_MAX_DIMENSIONS) return pdi__errpuc("too large","Very large image (corrupt?)");

   //   do a tiny bit of precessing
   if ( tga_image_type >= 8 )
   {
      tga_image_type -= 8;
      tga_is_RLE = 1;
   }
   tga_inverted = 1 - ((tga_inverted >> 5) & 1);

   //   If I'm paletted, then I'll use the number of bits from the palette
   if ( tga_indexed ) tga_comp = pdi__tga_get_comp(tga_palette_bits, 0, &tga_rgb16);
   else tga_comp = pdi__tga_get_comp(tga_bits_per_pixel, (tga_image_type == 3), &tga_rgb16);

   if(!tga_comp) // shouldn't really happen, pdi__tga_test() should have ensured basic consistency
      return pdi__errpuc("bad format", "Can't find out TGA pixelformat");

   //   tga info
   *x = tga_width;
   *y = tga_height;
   if (comp) *comp = tga_comp;

   if (!pdi__mad3sizes_valid(tga_width, tga_height, tga_comp, 0))
      return pdi__errpuc("too large", "Corrupt TGA");

   tga_data = (unsigned char*)pdi__malloc_mad3(tga_width, tga_height, tga_comp, 0);
   if (!tga_data) return pdi__errpuc("outofmem", "Out of memory");

   // skip to the data's starting position (offset usually = 0)
   pdi__skip(s, tga_offset );

   if ( !tga_indexed && !tga_is_RLE && !tga_rgb16 ) {
      for (i=0; i < tga_height; ++i) {
         int row = tga_inverted ? tga_height -i - 1 : i;
         pdi_uc *tga_row = tga_data + row*tga_width*tga_comp;
         pdi__getn(s, tga_row, tga_width * tga_comp);
      }
   } else  {
      //   do I need to load a palette?
      if ( tga_indexed)
      {
         if (tga_palette_len == 0) {  /* you have to have at least one entry! */
            PDI_FREE(tga_data);
            return pdi__errpuc("bad palette", "Corrupt TGA");
         }

         //   any data to skip? (offset usually = 0)
         pdi__skip(s, tga_palette_start );
         //   load the palette
         tga_palette = (unsigned char*)pdi__malloc_mad2(tga_palette_len, tga_comp, 0);
         if (!tga_palette) {
            PDI_FREE(tga_data);
            return pdi__errpuc("outofmem", "Out of memory");
         }
         if (tga_rgb16) {
            pdi_uc *pal_entry = tga_palette;
            PDI_ASSERT(tga_comp == PDI_rgb);
            for (i=0; i < tga_palette_len; ++i) {
               pdi__tga_read_rgb16(s, pal_entry);
               pal_entry += tga_comp;
            }
         } else if (!pdi__getn(s, tga_palette, tga_palette_len * tga_comp)) {
               PDI_FREE(tga_data);
               PDI_FREE(tga_palette);
               return pdi__errpuc("bad palette", "Corrupt TGA");
         }
      }
      //   load the data
      for (i=0; i < tga_width * tga_height; ++i)
      {
         //   if I'm in RLE mode, do I need to get a RLE pdi__pngchunk?
         if ( tga_is_RLE )
         {
            if ( RLE_count == 0 )
            {
               //   yep, get the next byte as a RLE command
               int RLE_cmd = pdi__get8(s);
               RLE_count = 1 + (RLE_cmd & 127);
               RLE_repeating = RLE_cmd >> 7;
               read_next_pixel = 1;
            } else if ( !RLE_repeating )
            {
               read_next_pixel = 1;
            }
         } else
         {
            read_next_pixel = 1;
         }
         //   OK, if I need to read a pixel, do it now
         if ( read_next_pixel )
         {
            //   load however much data we did have
            if ( tga_indexed )
            {
               // read in index, then perform the lookup
               int pal_idx = (tga_bits_per_pixel == 8) ? pdi__get8(s) : pdi__get16le(s);
               if ( pal_idx >= tga_palette_len ) {
                  // invalid index
                  pal_idx = 0;
               }
               pal_idx *= tga_comp;
               for (j = 0; j < tga_comp; ++j) {
                  raw_data[j] = tga_palette[pal_idx+j];
               }
            } else if(tga_rgb16) {
               PDI_ASSERT(tga_comp == PDI_rgb);
               pdi__tga_read_rgb16(s, raw_data);
            } else {
               //   read in the data raw
               for (j = 0; j < tga_comp; ++j) {
                  raw_data[j] = pdi__get8(s);
               }
            }
            //   clear the reading flag for the next pixel
            read_next_pixel = 0;
         } // end of reading a pixel

         // copy data
         for (j = 0; j < tga_comp; ++j)
           tga_data[i*tga_comp+j] = raw_data[j];

         //   in case we're in RLE mode, keep counting down
         --RLE_count;
      }
      //   do I need to invert the image?
      if ( tga_inverted )
      {
         for (j = 0; j*2 < tga_height; ++j)
         {
            int index1 = j * tga_width * tga_comp;
            int index2 = (tga_height - 1 - j) * tga_width * tga_comp;
            for (i = tga_width * tga_comp; i > 0; --i)
            {
               unsigned char temp = tga_data[index1];
               tga_data[index1] = tga_data[index2];
               tga_data[index2] = temp;
               ++index1;
               ++index2;
            }
         }
      }
      //   clear my palette, if I had one
      if ( tga_palette != NULL )
      {
         PDI_FREE( tga_palette );
      }
   }

   // swap RGB - if the source data was RGB16, it already is in the right order
   if (tga_comp >= 3 && !tga_rgb16)
   {
      unsigned char* tga_pixel = tga_data;
      for (i=0; i < tga_width * tga_height; ++i)
      {
         unsigned char temp = tga_pixel[0];
         tga_pixel[0] = tga_pixel[2];
         tga_pixel[2] = temp;
         tga_pixel += tga_comp;
      }
   }

   // convert to target component count
   if (req_comp && req_comp != tga_comp)
      tga_data = pdi__convert_format(tga_data, tga_comp, req_comp, tga_width, tga_height);

   //   the things I do to get rid of an error message, and yet keep
   //   Microsoft's C compilers happy... [8^(
   tga_palette_start = tga_palette_len = tga_palette_bits =
         tga_x_origin = tga_y_origin = 0;
   PDI_NOTUSED(tga_palette_start);
   //   OK, done
   return tga_data;
}
#endif

// *************************************************************************************************
// Photoshop PSD loader -- PD by Thatcher Ulrich, integration by Nicolas Schulz, tweaked by STB

#ifndef PDI_NO_PSD
static int pdi__psd_test(pdi__context *s)
{
   int r = (pdi__get32be(s) == 0x38425053);
   pdi__rewind(s);
   return r;
}

static int pdi__psd_decode_rle(pdi__context *s, pdi_uc *p, int pixelCount)
{
   int count, nleft, len;

   count = 0;
   while ((nleft = pixelCount - count) > 0) {
      len = pdi__get8(s);
      if (len == 128) {
         // No-op.
      } else if (len < 128) {
         // Copy next len+1 bytes literally.
         len++;
         if (len > nleft) return 0; // corrupt data
         count += len;
         while (len) {
            *p = pdi__get8(s);
            p += 4;
            len--;
         }
      } else if (len > 128) {
         pdi_uc   val;
         // Next -len+1 bytes in the dest are replicated from next source byte.
         // (Interpret len as a negative 8-bit int.)
         len = 257 - len;
         if (len > nleft) return 0; // corrupt data
         val = pdi__get8(s);
         count += len;
         while (len) {
            *p = val;
            p += 4;
            len--;
         }
      }
   }

   return 1;
}

static void *pdi__psd_load(pdi__context *s, int *x, int *y, int *comp, int req_comp, pdi__result_info *ri, int bpc)
{
   int pixelCount;
   int channelCount, compression;
   int channel, i;
   int bitdepth;
   int w,h;
   pdi_uc *out;
   PDI_NOTUSED(ri);

   // Check identifier
   if (pdi__get32be(s) != 0x38425053)   // "8BPS"
      return pdi__errpuc("not PSD", "Corrupt PSD image");

   // Check file type version.
   if (pdi__get16be(s) != 1)
      return pdi__errpuc("wrong version", "Unsupported version of PSD image");

   // Skip 6 reserved bytes.
   pdi__skip(s, 6 );

   // Read the number of channels (R, G, B, A, etc).
   channelCount = pdi__get16be(s);
   if (channelCount < 0 || channelCount > 16)
      return pdi__errpuc("wrong channel count", "Unsupported number of channels in PSD image");

   // Read the rows and columns of the image.
   h = pdi__get32be(s);
   w = pdi__get32be(s);

   if (h > PDI_MAX_DIMENSIONS) return pdi__errpuc("too large","Very large image (corrupt?)");
   if (w > PDI_MAX_DIMENSIONS) return pdi__errpuc("too large","Very large image (corrupt?)");

   // Make sure the depth is 8 bits.
   bitdepth = pdi__get16be(s);
   if (bitdepth != 8 && bitdepth != 16)
      return pdi__errpuc("unsupported bit depth", "PSD bit depth is not 8 or 16 bit");

   // Make sure the color mode is RGB.
   // Valid options are:
   //   0: Bitmap
   //   1: Grayscale
   //   2: Indexed color
   //   3: RGB color
   //   4: CMYK color
   //   7: Multichannel
   //   8: Duotone
   //   9: Lab color
   if (pdi__get16be(s) != 3)
      return pdi__errpuc("wrong color format", "PSD is not in RGB color format");

   // Skip the Mode Data.  (It's the palette for indexed color; other info for other modes.)
   pdi__skip(s,pdi__get32be(s) );

   // Skip the image resources.  (resolution, pen tool paths, etc)
   pdi__skip(s, pdi__get32be(s) );

   // Skip the reserved data.
   pdi__skip(s, pdi__get32be(s) );

   // Find out if the data is compressed.
   // Known values:
   //   0: no compression
   //   1: RLE compressed
   compression = pdi__get16be(s);
   if (compression > 1)
      return pdi__errpuc("bad compression", "PSD has an unknown compression format");

   // Check size
   if (!pdi__mad3sizes_valid(4, w, h, 0))
      return pdi__errpuc("too large", "Corrupt PSD");

   // Create the destination image.

   if (!compression && bitdepth == 16 && bpc == 16) {
      out = (pdi_uc *) pdi__malloc_mad3(8, w, h, 0);
      ri->bits_per_channel = 16;
   } else
      out = (pdi_uc *) pdi__malloc(4 * w*h);

   if (!out) return pdi__errpuc("outofmem", "Out of memory");
   pixelCount = w*h;

   // Initialize the data to zero.
   //memset( out, 0, pixelCount * 4 );

   // Finally, the image data.
   if (compression) {
      // RLE as used by .PSD and .TIFF
      // Loop until you get the number of unpacked bytes you are expecting:
      //     Read the next source byte into n.
      //     If n is between 0 and 127 inclusive, copy the next n+1 bytes literally.
      //     Else if n is between -127 and -1 inclusive, copy the next byte -n+1 times.
      //     Else if n is 128, noop.
      // Endloop

      // The RLE-compressed data is preceded by a 2-byte data count for each row in the data,
      // which we're going to just skip.
      pdi__skip(s, h * channelCount * 2 );

      // Read the RLE data by channel.
      for (channel = 0; channel < 4; channel++) {
         pdi_uc *p;

         p = out+channel;
         if (channel >= channelCount) {
            // Fill this channel with default data.
            for (i = 0; i < pixelCount; i++, p += 4)
               *p = (channel == 3 ? 255 : 0);
         } else {
            // Read the RLE data.
            if (!pdi__psd_decode_rle(s, p, pixelCount)) {
               PDI_FREE(out);
               return pdi__errpuc("corrupt", "bad RLE data");
            }
         }
      }

   } else {
      // We're at the raw image data.  It's each channel in order (Red, Green, Blue, Alpha, ...)
      // where each channel consists of an 8-bit (or 16-bit) value for each pixel in the image.

      // Read the data by channel.
      for (channel = 0; channel < 4; channel++) {
         if (channel >= channelCount) {
            // Fill this channel with default data.
            if (bitdepth == 16 && bpc == 16) {
               pdi__uint16 *q = ((pdi__uint16 *) out) + channel;
               pdi__uint16 val = channel == 3 ? 65535 : 0;
               for (i = 0; i < pixelCount; i++, q += 4)
                  *q = val;
            } else {
               pdi_uc *p = out+channel;
               pdi_uc val = channel == 3 ? 255 : 0;
               for (i = 0; i < pixelCount; i++, p += 4)
                  *p = val;
            }
         } else {
            if (ri->bits_per_channel == 16) {    // output bpc
               pdi__uint16 *q = ((pdi__uint16 *) out) + channel;
               for (i = 0; i < pixelCount; i++, q += 4)
                  *q = (pdi__uint16) pdi__get16be(s);
            } else {
               pdi_uc *p = out+channel;
               if (bitdepth == 16) {  // input bpc
                  for (i = 0; i < pixelCount; i++, p += 4)
                     *p = (pdi_uc) (pdi__get16be(s) >> 8);
               } else {
                  for (i = 0; i < pixelCount; i++, p += 4)
                     *p = pdi__get8(s);
               }
            }
         }
      }
   }

   // remove weird white matte from PSD
   if (channelCount >= 4) {
      if (ri->bits_per_channel == 16) {
         for (i=0; i < w*h; ++i) {
            pdi__uint16 *pixel = (pdi__uint16 *) out + 4*i;
            if (pixel[3] != 0 && pixel[3] != 65535) {
               float a = pixel[3] / 65535.0f;
               float ra = 1.0f / a;
               float inv_a = 65535.0f * (1 - ra);
               pixel[0] = (pdi__uint16) (pixel[0]*ra + inv_a);
               pixel[1] = (pdi__uint16) (pixel[1]*ra + inv_a);
               pixel[2] = (pdi__uint16) (pixel[2]*ra + inv_a);
            }
         }
      } else {
         for (i=0; i < w*h; ++i) {
            unsigned char *pixel = out + 4*i;
            if (pixel[3] != 0 && pixel[3] != 255) {
               float a = pixel[3] / 255.0f;
               float ra = 1.0f / a;
               float inv_a = 255.0f * (1 - ra);
               pixel[0] = (unsigned char) (pixel[0]*ra + inv_a);
               pixel[1] = (unsigned char) (pixel[1]*ra + inv_a);
               pixel[2] = (unsigned char) (pixel[2]*ra + inv_a);
            }
         }
      }
   }

   // convert to desired output format
   if (req_comp && req_comp != 4) {
      if (ri->bits_per_channel == 16)
         out = (pdi_uc *) pdi__convert_format16((pdi__uint16 *) out, 4, req_comp, w, h);
      else
         out = pdi__convert_format(out, 4, req_comp, w, h);
      if (out == NULL) return out; // pdi__convert_format frees input on failure
   }

   if (comp) *comp = 4;
   *y = h;
   *x = w;

   return out;
}
#endif

// *************************************************************************************************
// Softimage PIC loader
// by Tom Seddon
//
// See http://softimage.wiki.softimage.com/index.php/INFO:_PIC_file_format
// See http://ozviz.wasp.uwa.edu.au/~pbourke/dataformats/softimagepic/

#ifndef PDI_NO_PIC
static int pdi__pic_is4(pdi__context *s,const char *str)
{
   int i;
   for (i=0; i<4; ++i)
      if (pdi__get8(s) != (pdi_uc)str[i])
         return 0;

   return 1;
}

static int pdi__pic_test_core(pdi__context *s)
{
   int i;

   if (!pdi__pic_is4(s,"\x53\x80\xF6\x34"))
      return 0;

   for(i=0;i<84;++i)
      pdi__get8(s);

   if (!pdi__pic_is4(s,"PICT"))
      return 0;

   return 1;
}

typedef struct
{
   pdi_uc size,type,channel;
} pdi__pic_packet;

static pdi_uc *pdi__readval(pdi__context *s, int channel, pdi_uc *dest)
{
   int mask=0x80, i;

   for (i=0; i<4; ++i, mask>>=1) {
      if (channel & mask) {
         if (pdi__at_eof(s)) return pdi__errpuc("bad file","PIC file too short");
         dest[i]=pdi__get8(s);
      }
   }

   return dest;
}

static void pdi__copyval(int channel,pdi_uc *dest,const pdi_uc *src)
{
   int mask=0x80,i;

   for (i=0;i<4; ++i, mask>>=1)
      if (channel&mask)
         dest[i]=src[i];
}

static pdi_uc *pdi__pic_load_core(pdi__context *s,int width,int height,int *comp, pdi_uc *result)
{
   int act_comp=0,num_packets=0,y,chained;
   pdi__pic_packet packets[10];

   // this will (should...) cater for even some bizarre stuff like having data
    // for the same channel in multiple packets.
   do {
      pdi__pic_packet *packet;

      if (num_packets==sizeof(packets)/sizeof(packets[0]))
         return pdi__errpuc("bad format","too many packets");

      packet = &packets[num_packets++];

      chained = pdi__get8(s);
      packet->size    = pdi__get8(s);
      packet->type    = pdi__get8(s);
      packet->channel = pdi__get8(s);

      act_comp |= packet->channel;

      if (pdi__at_eof(s))          return pdi__errpuc("bad file","file too short (reading packets)");
      if (packet->size != 8)  return pdi__errpuc("bad format","packet isn't 8bpp");
   } while (chained);

   *comp = (act_comp & 0x10 ? 4 : 3); // has alpha channel?

   for(y=0; y<height; ++y) {
      int packet_idx;

      for(packet_idx=0; packet_idx < num_packets; ++packet_idx) {
         pdi__pic_packet *packet = &packets[packet_idx];
         pdi_uc *dest = result+y*width*4;

         switch (packet->type) {
            default:
               return pdi__errpuc("bad format","packet has bad compression type");

            case 0: {//uncompressed
               int x;

               for(x=0;x<width;++x, dest+=4)
                  if (!pdi__readval(s,packet->channel,dest))
                     return 0;
               break;
            }

            case 1://Pure RLE
               {
                  int left=width, i;

                  while (left>0) {
                     pdi_uc count,value[4];

                     count=pdi__get8(s);
                     if (pdi__at_eof(s))   return pdi__errpuc("bad file","file too short (pure read count)");

                     if (count > left)
                        count = (pdi_uc) left;

                     if (!pdi__readval(s,packet->channel,value))  return 0;

                     for(i=0; i<count; ++i,dest+=4)
                        pdi__copyval(packet->channel,dest,value);
                     left -= count;
                  }
               }
               break;

            case 2: {//Mixed RLE
               int left=width;
               while (left>0) {
                  int count = pdi__get8(s), i;
                  if (pdi__at_eof(s))  return pdi__errpuc("bad file","file too short (mixed read count)");

                  if (count >= 128) { // Repeated
                     pdi_uc value[4];

                     if (count==128)
                        count = pdi__get16be(s);
                     else
                        count -= 127;
                     if (count > left)
                        return pdi__errpuc("bad file","scanline overrun");

                     if (!pdi__readval(s,packet->channel,value))
                        return 0;

                     for(i=0;i<count;++i, dest += 4)
                        pdi__copyval(packet->channel,dest,value);
                  } else { // Raw
                     ++count;
                     if (count>left) return pdi__errpuc("bad file","scanline overrun");

                     for(i=0;i<count;++i, dest+=4)
                        if (!pdi__readval(s,packet->channel,dest))
                           return 0;
                  }
                  left-=count;
               }
               break;
            }
         }
      }
   }

   return result;
}

static void *pdi__pic_load(pdi__context *s,int *px,int *py,int *comp,int req_comp, pdi__result_info *ri)
{
   pdi_uc *result;
   int i, x,y, internal_comp;
   PDI_NOTUSED(ri);

   if (!comp) comp = &internal_comp;

   for (i=0; i<92; ++i)
      pdi__get8(s);

   x = pdi__get16be(s);
   y = pdi__get16be(s);

   if (y > PDI_MAX_DIMENSIONS) return pdi__errpuc("too large","Very large image (corrupt?)");
   if (x > PDI_MAX_DIMENSIONS) return pdi__errpuc("too large","Very large image (corrupt?)");

   if (pdi__at_eof(s))  return pdi__errpuc("bad file","file too short (pic header)");
   if (!pdi__mad3sizes_valid(x, y, 4, 0)) return pdi__errpuc("too large", "PIC image too large to decode");

   pdi__get32be(s); //skip `ratio'
   pdi__get16be(s); //skip `fields'
   pdi__get16be(s); //skip `pad'

   // intermediate buffer is RGBA
   result = (pdi_uc *) pdi__malloc_mad3(x, y, 4, 0);
   if (!result) return pdi__errpuc("outofmem", "Out of memory");
   memset(result, 0xff, x*y*4);

   if (!pdi__pic_load_core(s,x,y,comp, result)) {
      PDI_FREE(result);
      result=0;
   }
   *px = x;
   *py = y;
   if (req_comp == 0) req_comp = *comp;
   result=pdi__convert_format(result,4,req_comp,x,y);

   return result;
}

static int pdi__pic_test(pdi__context *s)
{
   int r = pdi__pic_test_core(s);
   pdi__rewind(s);
   return r;
}
#endif

// *************************************************************************************************
// GIF loader -- public domain by Jean-Marc Lienher -- simplified/shrunk by stb

#ifndef PDI_NO_GIF
typedef struct
{
   pdi__int16 prefix;
   pdi_uc first;
   pdi_uc suffix;
} pdi__gif_lzw;

typedef struct
{
   int w,h;
   pdi_uc *out;                 // output buffer (always 4 components)
   pdi_uc *background;          // The current "background" as far as a gif is concerned
   pdi_uc *history;
   int flags, bgindex, ratio, transparent, eflags;
   pdi_uc  pal[256][4];
   pdi_uc lpal[256][4];
   pdi__gif_lzw codes[8192];
   pdi_uc *color_table;
   int parse, step;
   int lflags;
   int start_x, start_y;
   int max_x, max_y;
   int cur_x, cur_y;
   int line_size;
   int delay;
} pdi__gif;

static int pdi__gif_test_raw(pdi__context *s)
{
   int sz;
   if (pdi__get8(s) != 'G' || pdi__get8(s) != 'I' || pdi__get8(s) != 'F' || pdi__get8(s) != '8') return 0;
   sz = pdi__get8(s);
   if (sz != '9' && sz != '7') return 0;
   if (pdi__get8(s) != 'a') return 0;
   return 1;
}

static int pdi__gif_test(pdi__context *s)
{
   int r = pdi__gif_test_raw(s);
   pdi__rewind(s);
   return r;
}

static void pdi__gif_parse_colortable(pdi__context *s, pdi_uc pal[256][4], int num_entries, int transp)
{
   int i;
   for (i=0; i < num_entries; ++i) {
      pal[i][2] = pdi__get8(s);
      pal[i][1] = pdi__get8(s);
      pal[i][0] = pdi__get8(s);
      pal[i][3] = transp == i ? 0 : 255;
   }
}

static int pdi__gif_header(pdi__context *s, pdi__gif *g, int *comp, int is_info)
{
   pdi_uc version;
   if (pdi__get8(s) != 'G' || pdi__get8(s) != 'I' || pdi__get8(s) != 'F' || pdi__get8(s) != '8')
      return pdi__err("not GIF", "Corrupt GIF");

   version = pdi__get8(s);
   if (version != '7' && version != '9')    return pdi__err("not GIF", "Corrupt GIF");
   if (pdi__get8(s) != 'a')                return pdi__err("not GIF", "Corrupt GIF");

   pdi__g_failure_reason = "";
   g->w = pdi__get16le(s);
   g->h = pdi__get16le(s);
   g->flags = pdi__get8(s);
   g->bgindex = pdi__get8(s);
   g->ratio = pdi__get8(s);
   g->transparent = -1;

   if (g->w > PDI_MAX_DIMENSIONS) return pdi__err("too large","Very large image (corrupt?)");
   if (g->h > PDI_MAX_DIMENSIONS) return pdi__err("too large","Very large image (corrupt?)");

   if (comp != 0) *comp = 4;  // can't actually tell whether it's 3 or 4 until we parse the comments

   if (is_info) return 1;

   if (g->flags & 0x80)
      pdi__gif_parse_colortable(s,g->pal, 2 << (g->flags & 7), -1);

   return 1;
}

static int pdi__gif_info_raw(pdi__context *s, int *x, int *y, int *comp)
{
   pdi__gif* g = (pdi__gif*) pdi__malloc(sizeof(pdi__gif));
   if (!g) return pdi__err("outofmem", "Out of memory");
   if (!pdi__gif_header(s, g, comp, 1)) {
      PDI_FREE(g);
      pdi__rewind( s );
      return 0;
   }
   if (x) *x = g->w;
   if (y) *y = g->h;
   PDI_FREE(g);
   return 1;
}

static void pdi__out_gif_code(pdi__gif *g, pdi__uint16 code)
{
   pdi_uc *p, *c;
   int idx;

   // recurse to decode the prefixes, since the linked-list is backwards,
   // and working backwards through an interleaved image would be nasty
   if (g->codes[code].prefix >= 0)
      pdi__out_gif_code(g, g->codes[code].prefix);

   if (g->cur_y >= g->max_y) return;

   idx = g->cur_x + g->cur_y;
   p = &g->out[idx];
   g->history[idx / 4] = 1;

   c = &g->color_table[g->codes[code].suffix * 4];
   if (c[3] > 128) { // don't render transparent pixels;
      p[0] = c[2];
      p[1] = c[1];
      p[2] = c[0];
      p[3] = c[3];
   }
   g->cur_x += 4;

   if (g->cur_x >= g->max_x) {
      g->cur_x = g->start_x;
      g->cur_y += g->step;

      while (g->cur_y >= g->max_y && g->parse > 0) {
         g->step = (1 << g->parse) * g->line_size;
         g->cur_y = g->start_y + (g->step >> 1);
         --g->parse;
      }
   }
}

static pdi_uc *pdi__process_gif_raster(pdi__context *s, pdi__gif *g)
{
   pdi_uc lzw_cs;
   pdi__int32 len, init_code;
   pdi__uint32 first;
   pdi__int32 codesize, codemask, avail, oldcode, bits, valid_bits, clear;
   pdi__gif_lzw *p;

   lzw_cs = pdi__get8(s);
   if (lzw_cs > 12) return NULL;
   clear = 1 << lzw_cs;
   first = 1;
   codesize = lzw_cs + 1;
   codemask = (1 << codesize) - 1;
   bits = 0;
   valid_bits = 0;
   for (init_code = 0; init_code < clear; init_code++) {
      g->codes[init_code].prefix = -1;
      g->codes[init_code].first = (pdi_uc) init_code;
      g->codes[init_code].suffix = (pdi_uc) init_code;
   }

   // support no starting clear code
   avail = clear+2;
   oldcode = -1;

   len = 0;
   for(;;) {
      if (valid_bits < codesize) {
         if (len == 0) {
            len = pdi__get8(s); // start new block
            if (len == 0)
               return g->out;
         }
         --len;
         bits |= (pdi__int32) pdi__get8(s) << valid_bits;
         valid_bits += 8;
      } else {
         pdi__int32 code = bits & codemask;
         bits >>= codesize;
         valid_bits -= codesize;
         // @OPTIMIZE: is there some way we can accelerate the non-clear path?
         if (code == clear) {  // clear code
            codesize = lzw_cs + 1;
            codemask = (1 << codesize) - 1;
            avail = clear + 2;
            oldcode = -1;
            first = 0;
         } else if (code == clear + 1) { // end of stream code
            pdi__skip(s, len);
            while ((len = pdi__get8(s)) > 0)
               pdi__skip(s,len);
            return g->out;
         } else if (code <= avail) {
            if (first) {
               return pdi__errpuc("no clear code", "Corrupt GIF");
            }

            if (oldcode >= 0) {
               p = &g->codes[avail++];
               if (avail > 8192) {
                  return pdi__errpuc("too many codes", "Corrupt GIF");
               }

               p->prefix = (pdi__int16) oldcode;
               p->first = g->codes[oldcode].first;
               p->suffix = (code == avail) ? p->first : g->codes[code].first;
            } else if (code == avail)
               return pdi__errpuc("illegal code in raster", "Corrupt GIF");

            pdi__out_gif_code(g, (pdi__uint16) code);

            if ((avail & codemask) == 0 && avail <= 0x0FFF) {
               codesize++;
               codemask = (1 << codesize) - 1;
            }

            oldcode = code;
         } else {
            return pdi__errpuc("illegal code in raster", "Corrupt GIF");
         }
      }
   }
}

// this function is designed to support animated gifs, although stb_image doesn't support it
// two back is the image from two frames ago, used for a very specific disposal format
static pdi_uc *pdi__gif_load_next(pdi__context *s, pdi__gif *g, int *comp, int req_comp, pdi_uc *two_back)
{
   int dispose;
   int first_frame;
   int pi;
   int pcount;
   PDI_NOTUSED(req_comp);

   // on first frame, any non-written pixels get the background colour (non-transparent)
   first_frame = 0;
   if (g->out == 0) {
      if (!pdi__gif_header(s, g, comp,0)) return 0; // pdi__g_failure_reason set by pdi__gif_header
      if (!pdi__mad3sizes_valid(4, g->w, g->h, 0))
         return pdi__errpuc("too large", "GIF image is too large");
      pcount = g->w * g->h;
      g->out = (pdi_uc *) pdi__malloc(4 * pcount);
      g->background = (pdi_uc *) pdi__malloc(4 * pcount);
      g->history = (pdi_uc *) pdi__malloc(pcount);
      if (!g->out || !g->background || !g->history)
         return pdi__errpuc("outofmem", "Out of memory");

      // image is treated as "transparent" at the start - ie, nothing overwrites the current background;
      // background colour is only used for pixels that are not rendered first frame, after that "background"
      // color refers to the color that was there the previous frame.
      memset(g->out, 0x00, 4 * pcount);
      memset(g->background, 0x00, 4 * pcount); // state of the background (starts transparent)
      memset(g->history, 0x00, pcount);        // pixels that were affected previous frame
      first_frame = 1;
   } else {
      // second frame - how do we dispose of the previous one?
      dispose = (g->eflags & 0x1C) >> 2;
      pcount = g->w * g->h;

      if ((dispose == 3) && (two_back == 0)) {
         dispose = 2; // if I don't have an image to revert back to, default to the old background
      }

      if (dispose == 3) { // use previous graphic
         for (pi = 0; pi < pcount; ++pi) {
            if (g->history[pi]) {
               memcpy( &g->out[pi * 4], &two_back[pi * 4], 4 );
            }
         }
      } else if (dispose == 2) {
         // restore what was changed last frame to background before that frame;
         for (pi = 0; pi < pcount; ++pi) {
            if (g->history[pi]) {
               memcpy( &g->out[pi * 4], &g->background[pi * 4], 4 );
            }
         }
      } else {
         // This is a non-disposal case eithe way, so just
         // leave the pixels as is, and they will become the new background
         // 1: do not dispose
         // 0:  not specified.
      }

      // background is what out is after the undoing of the previou frame;
      memcpy( g->background, g->out, 4 * g->w * g->h );
   }

   // clear my history;
   memset( g->history, 0x00, g->w * g->h );        // pixels that were affected previous frame

   for (;;) {
      int tag = pdi__get8(s);
      switch (tag) {
         case 0x2C: /* Image Descriptor */
         {
            pdi__int32 x, y, w, h;
            pdi_uc *o;

            x = pdi__get16le(s);
            y = pdi__get16le(s);
            w = pdi__get16le(s);
            h = pdi__get16le(s);
            if (((x + w) > (g->w)) || ((y + h) > (g->h)))
               return pdi__errpuc("bad Image Descriptor", "Corrupt GIF");

            g->line_size = g->w * 4;
            g->start_x = x * 4;
            g->start_y = y * g->line_size;
            g->max_x   = g->start_x + w * 4;
            g->max_y   = g->start_y + h * g->line_size;
            g->cur_x   = g->start_x;
            g->cur_y   = g->start_y;

            // if the width of the specified rectangle is 0, that means
            // we may not see *any* pixels or the image is malformed;
            // to make sure this is caught, move the current y down to
            // max_y (which is what out_gif_code checks).
            if (w == 0)
               g->cur_y = g->max_y;

            g->lflags = pdi__get8(s);

            if (g->lflags & 0x40) {
               g->step = 8 * g->line_size; // first interlaced spacing
               g->parse = 3;
            } else {
               g->step = g->line_size;
               g->parse = 0;
            }

            if (g->lflags & 0x80) {
               pdi__gif_parse_colortable(s,g->lpal, 2 << (g->lflags & 7), g->eflags & 0x01 ? g->transparent : -1);
               g->color_table = (pdi_uc *) g->lpal;
            } else if (g->flags & 0x80) {
               g->color_table = (pdi_uc *) g->pal;
            } else
               return pdi__errpuc("missing color table", "Corrupt GIF");

            o = pdi__process_gif_raster(s, g);
            if (!o) return NULL;

            // if this was the first frame,
            pcount = g->w * g->h;
            if (first_frame && (g->bgindex > 0)) {
               // if first frame, any pixel not drawn to gets the background color
               for (pi = 0; pi < pcount; ++pi) {
                  if (g->history[pi] == 0) {
                     g->pal[g->bgindex][3] = 255; // just in case it was made transparent, undo that; It will be reset next frame if need be;
                     memcpy( &g->out[pi * 4], &g->pal[g->bgindex], 4 );
                  }
               }
            }

            return o;
         }

         case 0x21: // Comment Extension.
         {
            int len;
            int ext = pdi__get8(s);
            if (ext == 0xF9) { // Graphic Control Extension.
               len = pdi__get8(s);
               if (len == 4) {
                  g->eflags = pdi__get8(s);
                  g->delay = 10 * pdi__get16le(s); // delay - 1/100th of a second, saving as 1/1000ths.

                  // unset old transparent
                  if (g->transparent >= 0) {
                     g->pal[g->transparent][3] = 255;
                  }
                  if (g->eflags & 0x01) {
                     g->transparent = pdi__get8(s);
                     if (g->transparent >= 0) {
                        g->pal[g->transparent][3] = 0;
                     }
                  } else {
                     // don't need transparent
                     pdi__skip(s, 1);
                     g->transparent = -1;
                  }
               } else {
                  pdi__skip(s, len);
                  break;
               }
            }
            while ((len = pdi__get8(s)) != 0) {
               pdi__skip(s, len);
            }
            break;
         }

         case 0x3B: // gif stream termination code
            return (pdi_uc *) s; // using '1' causes warning on some compilers

         default:
            return pdi__errpuc("unknown code", "Corrupt GIF");
      }
   }
}

static void *pdi__load_gif_main_outofmem(pdi__gif *g, pdi_uc *out, int **delays)
{
   PDI_FREE(g->out);
   PDI_FREE(g->history);
   PDI_FREE(g->background);

   if (out) PDI_FREE(out);
   if (delays && *delays) PDI_FREE(*delays);
   return pdi__errpuc("outofmem", "Out of memory");
}

static void *pdi__load_gif_main(pdi__context *s, int **delays, int *x, int *y, int *z, int *comp, int req_comp)
{
   if (pdi__gif_test(s)) {
      int layers = 0;
      pdi_uc *u = 0;
      pdi_uc *out = 0;
      pdi_uc *two_back = 0;
      pdi__gif g;
      int stride;
      int out_size = 0;
      int delays_size = 0;

      PDI_NOTUSED(out_size);
      PDI_NOTUSED(delays_size);

      memset(&g, 0, sizeof(g));
      if (delays) {
         *delays = 0;
      }

      do {
         u = pdi__gif_load_next(s, &g, comp, req_comp, two_back);
         if (u == (pdi_uc *) s) u = 0;  // end of animated gif marker

         if (u) {
            *x = g.w;
            *y = g.h;
            ++layers;
            stride = g.w * g.h * 4;

            if (out) {
               void *tmp = (pdi_uc*) PDI_REALLOC_SIZED( out, out_size, layers * stride );
               if (!tmp)
                  return pdi__load_gif_main_outofmem(&g, out, delays);
               else {
                   out = (pdi_uc*) tmp;
                   out_size = layers * stride;
               }

               if (delays) {
                  int *new_delays = (int*) PDI_REALLOC_SIZED( *delays, delays_size, sizeof(int) * layers );
                  if (!new_delays)
                     return pdi__load_gif_main_outofmem(&g, out, delays);
                  *delays = new_delays;
                  delays_size = layers * sizeof(int);
               }
            } else {
               out = (pdi_uc*)pdi__malloc( layers * stride );
               if (!out)
                  return pdi__load_gif_main_outofmem(&g, out, delays);
               out_size = layers * stride;
               if (delays) {
                  *delays = (int*) pdi__malloc( layers * sizeof(int) );
                  if (!*delays)
                     return pdi__load_gif_main_outofmem(&g, out, delays);
                  delays_size = layers * sizeof(int);
               }
            }
            memcpy( out + ((layers - 1) * stride), u, stride );
            if (layers >= 2) {
               two_back = out - 2 * stride;
            }

            if (delays) {
               (*delays)[layers - 1U] = g.delay;
            }
         }
      } while (u != 0);

      // free temp buffer;
      PDI_FREE(g.out);
      PDI_FREE(g.history);
      PDI_FREE(g.background);

      // do the final conversion after loading everything;
      if (req_comp && req_comp != 4)
         out = pdi__convert_format(out, 4, req_comp, layers * g.w, g.h);

      *z = layers;
      return out;
   } else {
      return pdi__errpuc("not GIF", "Image was not as a gif type.");
   }
}

static void *pdi__gif_load(pdi__context *s, int *x, int *y, int *comp, int req_comp, pdi__result_info *ri)
{
   pdi_uc *u = 0;
   pdi__gif g;
   memset(&g, 0, sizeof(g));
   PDI_NOTUSED(ri);

   u = pdi__gif_load_next(s, &g, comp, req_comp, 0);
   if (u == (pdi_uc *) s) u = 0;  // end of animated gif marker
   if (u) {
      *x = g.w;
      *y = g.h;

      // moved conversion to after successful load so that the same
      // can be done for multiple frames.
      if (req_comp && req_comp != 4)
         u = pdi__convert_format(u, 4, req_comp, g.w, g.h);
   } else if (g.out) {
      // if there was an error and we allocated an image buffer, free it!
      PDI_FREE(g.out);
   }

   // free buffers needed for multiple frame loading;
   PDI_FREE(g.history);
   PDI_FREE(g.background);

   return u;
}

static int pdi__gif_info(pdi__context *s, int *x, int *y, int *comp)
{
   return pdi__gif_info_raw(s,x,y,comp);
}
#endif

// *************************************************************************************************
// Radiance RGBE HDR loader
// originally by Nicolas Schulz
#ifndef PDI_NO_HDR
static int pdi__hdr_test_core(pdi__context *s, const char *signature)
{
   int i;
   for (i=0; signature[i]; ++i)
      if (pdi__get8(s) != signature[i])
          return 0;
   pdi__rewind(s);
   return 1;
}

static int pdi__hdr_test(pdi__context* s)
{
   int r = pdi__hdr_test_core(s, "#?RADIANCE\n");
   pdi__rewind(s);
   if(!r) {
       r = pdi__hdr_test_core(s, "#?RGBE\n");
       pdi__rewind(s);
   }
   return r;
}

#define PDI__HDR_BUFLEN  1024
static char *pdi__hdr_gettoken(pdi__context *z, char *buffer)
{
   int len=0;
   char c = '\0';

   c = (char) pdi__get8(z);

   while (!pdi__at_eof(z) && c != '\n') {
      buffer[len++] = c;
      if (len == PDI__HDR_BUFLEN-1) {
         // flush to end of line
         while (!pdi__at_eof(z) && pdi__get8(z) != '\n')
            ;
         break;
      }
      c = (char) pdi__get8(z);
   }

   buffer[len] = 0;
   return buffer;
}

static void pdi__hdr_convert(float *output, pdi_uc *input, int req_comp)
{
   if ( input[3] != 0 ) {
      float f1;
      // Exponent
      f1 = (float) ldexp(1.0f, input[3] - (int)(128 + 8));
      if (req_comp <= 2)
         output[0] = (input[0] + input[1] + input[2]) * f1 / 3;
      else {
         output[0] = input[0] * f1;
         output[1] = input[1] * f1;
         output[2] = input[2] * f1;
      }
      if (req_comp == 2) output[1] = 1;
      if (req_comp == 4) output[3] = 1;
   } else {
      switch (req_comp) {
         case 4: output[3] = 1; /* fallthrough */
         case 3: output[0] = output[1] = output[2] = 0;
                 break;
         case 2: output[1] = 1; /* fallthrough */
         case 1: output[0] = 0;
                 break;
      }
   }
}

static float *pdi__hdr_load(pdi__context *s, int *x, int *y, int *comp, int req_comp, pdi__result_info *ri)
{
   char buffer[PDI__HDR_BUFLEN];
   char *token;
   int valid = 0;
   int width, height;
   pdi_uc *scanline;
   float *hdr_data;
   int len;
   unsigned char count, value;
   int i, j, k, c1,c2, z;
   const char *headerToken;
   PDI_NOTUSED(ri);

   // Check identifier
   headerToken = pdi__hdr_gettoken(s,buffer);
   if (strcmp(headerToken, "#?RADIANCE") != 0 && strcmp(headerToken, "#?RGBE") != 0)
      return pdi__errpf("not HDR", "Corrupt HDR image");

   // Parse header
   for(;;) {
      token = pdi__hdr_gettoken(s,buffer);
      if (token[0] == 0) break;
      if (strcmp(token, "FORMAT=32-bit_rle_rgbe") == 0) valid = 1;
   }

   if (!valid)    return pdi__errpf("unsupported format", "Unsupported HDR format");

   // Parse width and height
   // can't use sscanf() if we're not using stdio!
   token = pdi__hdr_gettoken(s,buffer);
   if (strncmp(token, "-Y ", 3))  return pdi__errpf("unsupported data layout", "Unsupported HDR format");
   token += 3;
   height = (int) strtol(token, &token, 10);
   while (*token == ' ') ++token;
   if (strncmp(token, "+X ", 3))  return pdi__errpf("unsupported data layout", "Unsupported HDR format");
   token += 3;
   width = (int) strtol(token, NULL, 10);

   if (height > PDI_MAX_DIMENSIONS) return pdi__errpf("too large","Very large image (corrupt?)");
   if (width > PDI_MAX_DIMENSIONS) return pdi__errpf("too large","Very large image (corrupt?)");

   *x = width;
   *y = height;

   if (comp) *comp = 3;
   if (req_comp == 0) req_comp = 3;

   if (!pdi__mad4sizes_valid(width, height, req_comp, sizeof(float), 0))
      return pdi__errpf("too large", "HDR image is too large");

   // Read data
   hdr_data = (float *) pdi__malloc_mad4(width, height, req_comp, sizeof(float), 0);
   if (!hdr_data)
      return pdi__errpf("outofmem", "Out of memory");

   // Load image data
   // image data is stored as some number of sca
   if ( width < 8 || width >= 32768) {
      // Read flat data
      for (j=0; j < height; ++j) {
         for (i=0; i < width; ++i) {
            pdi_uc rgbe[4];
           main_decode_loop:
            pdi__getn(s, rgbe, 4);
            pdi__hdr_convert(hdr_data + j * width * req_comp + i * req_comp, rgbe, req_comp);
         }
      }
   } else {
      // Read RLE-encoded data
      scanline = NULL;

      for (j = 0; j < height; ++j) {
         c1 = pdi__get8(s);
         c2 = pdi__get8(s);
         len = pdi__get8(s);
         if (c1 != 2 || c2 != 2 || (len & 0x80)) {
            // not run-length encoded, so we have to actually use THIS data as a decoded
            // pixel (note this can't be a valid pixel--one of RGB must be >= 128)
            pdi_uc rgbe[4];
            rgbe[0] = (pdi_uc) c1;
            rgbe[1] = (pdi_uc) c2;
            rgbe[2] = (pdi_uc) len;
            rgbe[3] = (pdi_uc) pdi__get8(s);
            pdi__hdr_convert(hdr_data, rgbe, req_comp);
            i = 1;
            j = 0;
            PDI_FREE(scanline);
            goto main_decode_loop; // yes, this makes no sense
         }
         len <<= 8;
         len |= pdi__get8(s);
         if (len != width) { PDI_FREE(hdr_data); PDI_FREE(scanline); return pdi__errpf("invalid decoded scanline length", "corrupt HDR"); }
         if (scanline == NULL) {
            scanline = (pdi_uc *) pdi__malloc_mad2(width, 4, 0);
            if (!scanline) {
               PDI_FREE(hdr_data);
               return pdi__errpf("outofmem", "Out of memory");
            }
         }

         for (k = 0; k < 4; ++k) {
            int nleft;
            i = 0;
            while ((nleft = width - i) > 0) {
               count = pdi__get8(s);
               if (count > 128) {
                  // Run
                  value = pdi__get8(s);
                  count -= 128;
                  if ((count == 0) || (count > nleft)) { PDI_FREE(hdr_data); PDI_FREE(scanline); return pdi__errpf("corrupt", "bad RLE data in HDR"); }
                  for (z = 0; z < count; ++z)
                     scanline[i++ * 4 + k] = value;
               } else {
                  // Dump
                  if ((count == 0) || (count > nleft)) { PDI_FREE(hdr_data); PDI_FREE(scanline); return pdi__errpf("corrupt", "bad RLE data in HDR"); }
                  for (z = 0; z < count; ++z)
                     scanline[i++ * 4 + k] = pdi__get8(s);
               }
            }
         }
         for (i=0; i < width; ++i)
            pdi__hdr_convert(hdr_data+(j*width + i)*req_comp, scanline + i*4, req_comp);
      }
      if (scanline)
         PDI_FREE(scanline);
   }

   return hdr_data;
}

static int pdi__hdr_info(pdi__context *s, int *x, int *y, int *comp)
{
   char buffer[PDI__HDR_BUFLEN];
   char *token;
   int valid = 0;
   int dummy;

   if (!x) x = &dummy;
   if (!y) y = &dummy;
   if (!comp) comp = &dummy;

   if (pdi__hdr_test(s) == 0) {
       pdi__rewind( s );
       return 0;
   }

   for(;;) {
      token = pdi__hdr_gettoken(s,buffer);
      if (token[0] == 0) break;
      if (strcmp(token, "FORMAT=32-bit_rle_rgbe") == 0) valid = 1;
   }

   if (!valid) {
       pdi__rewind( s );
       return 0;
   }
   token = pdi__hdr_gettoken(s,buffer);
   if (strncmp(token, "-Y ", 3)) {
       pdi__rewind( s );
       return 0;
   }
   token += 3;
   *y = (int) strtol(token, &token, 10);
   while (*token == ' ') ++token;
   if (strncmp(token, "+X ", 3)) {
       pdi__rewind( s );
       return 0;
   }
   token += 3;
   *x = (int) strtol(token, NULL, 10);
   *comp = 3;
   return 1;
}
#endif // PDI_NO_HDR

#ifndef PDI_NO_BMP
static int pdi__bmp_info(pdi__context *s, int *x, int *y, int *comp)
{
   void *p;
   pdi__bmp_data info;

   info.all_a = 255;
   p = pdi__bmp_parse_header(s, &info);
   if (p == NULL) {
      pdi__rewind( s );
      return 0;
   }
   if (x) *x = s->img_x;
   if (y) *y = s->img_y;
   if (comp) {
      if (info.bpp == 24 && info.ma == 0xff000000)
         *comp = 3;
      else
         *comp = info.ma ? 4 : 3;
   }
   return 1;
}
#endif

#ifndef PDI_NO_PSD
static int pdi__psd_info(pdi__context *s, int *x, int *y, int *comp)
{
   int channelCount, dummy, depth;
   if (!x) x = &dummy;
   if (!y) y = &dummy;
   if (!comp) comp = &dummy;
   if (pdi__get32be(s) != 0x38425053) {
       pdi__rewind( s );
       return 0;
   }
   if (pdi__get16be(s) != 1) {
       pdi__rewind( s );
       return 0;
   }
   pdi__skip(s, 6);
   channelCount = pdi__get16be(s);
   if (channelCount < 0 || channelCount > 16) {
       pdi__rewind( s );
       return 0;
   }
   *y = pdi__get32be(s);
   *x = pdi__get32be(s);
   depth = pdi__get16be(s);
   if (depth != 8 && depth != 16) {
       pdi__rewind( s );
       return 0;
   }
   if (pdi__get16be(s) != 3) {
       pdi__rewind( s );
       return 0;
   }
   *comp = 4;
   return 1;
}

static int pdi__psd_is16(pdi__context *s)
{
   int channelCount, depth;
   if (pdi__get32be(s) != 0x38425053) {
       pdi__rewind( s );
       return 0;
   }
   if (pdi__get16be(s) != 1) {
       pdi__rewind( s );
       return 0;
   }
   pdi__skip(s, 6);
   channelCount = pdi__get16be(s);
   if (channelCount < 0 || channelCount > 16) {
       pdi__rewind( s );
       return 0;
   }
   PDI_NOTUSED(pdi__get32be(s));
   PDI_NOTUSED(pdi__get32be(s));
   depth = pdi__get16be(s);
   if (depth != 16) {
       pdi__rewind( s );
       return 0;
   }
   return 1;
}
#endif

#ifndef PDI_NO_PIC
static int pdi__pic_info(pdi__context *s, int *x, int *y, int *comp)
{
   int act_comp=0,num_packets=0,chained,dummy;
   pdi__pic_packet packets[10];

   if (!x) x = &dummy;
   if (!y) y = &dummy;
   if (!comp) comp = &dummy;

   if (!pdi__pic_is4(s,"\x53\x80\xF6\x34")) {
      pdi__rewind(s);
      return 0;
   }

   pdi__skip(s, 88);

   *x = pdi__get16be(s);
   *y = pdi__get16be(s);
   if (pdi__at_eof(s)) {
      pdi__rewind( s);
      return 0;
   }
   if ( (*x) != 0 && (1 << 28) / (*x) < (*y)) {
      pdi__rewind( s );
      return 0;
   }

   pdi__skip(s, 8);

   do {
      pdi__pic_packet *packet;

      if (num_packets==sizeof(packets)/sizeof(packets[0]))
         return 0;

      packet = &packets[num_packets++];
      chained = pdi__get8(s);
      packet->size    = pdi__get8(s);
      packet->type    = pdi__get8(s);
      packet->channel = pdi__get8(s);
      act_comp |= packet->channel;

      if (pdi__at_eof(s)) {
          pdi__rewind( s );
          return 0;
      }
      if (packet->size != 8) {
          pdi__rewind( s );
          return 0;
      }
   } while (chained);

   *comp = (act_comp & 0x10 ? 4 : 3);

   return 1;
}
#endif

// *************************************************************************************************
// Portable Gray Map and Portable Pixel Map loader
// by Ken Miller
//
// PGM: http://netpbm.sourceforge.net/doc/pgm.html
// PPM: http://netpbm.sourceforge.net/doc/ppm.html
//
// Known limitations:
//    Does not support comments in the header section
//    Does not support ASCII image data (formats P2 and P3)

#ifndef PDI_NO_PNM

static int      pdi__pnm_test(pdi__context *s)
{
   char p, t;
   p = (char) pdi__get8(s);
   t = (char) pdi__get8(s);
   if (p != 'P' || (t != '5' && t != '6')) {
       pdi__rewind( s );
       return 0;
   }
   return 1;
}

static void *pdi__pnm_load(pdi__context *s, int *x, int *y, int *comp, int req_comp, pdi__result_info *ri)
{
   pdi_uc *out;
   PDI_NOTUSED(ri);

   ri->bits_per_channel = pdi__pnm_info(s, (int *)&s->img_x, (int *)&s->img_y, (int *)&s->img_n);
   if (ri->bits_per_channel == 0)
      return 0;

   if (s->img_y > PDI_MAX_DIMENSIONS) return pdi__errpuc("too large","Very large image (corrupt?)");
   if (s->img_x > PDI_MAX_DIMENSIONS) return pdi__errpuc("too large","Very large image (corrupt?)");

   *x = s->img_x;
   *y = s->img_y;
   if (comp) *comp = s->img_n;

   if (!pdi__mad4sizes_valid(s->img_n, s->img_x, s->img_y, ri->bits_per_channel / 8, 0))
      return pdi__errpuc("too large", "PNM too large");

   out = (pdi_uc *) pdi__malloc_mad4(s->img_n, s->img_x, s->img_y, ri->bits_per_channel / 8, 0);
   if (!out) return pdi__errpuc("outofmem", "Out of memory");
   if (!pdi__getn(s, out, s->img_n * s->img_x * s->img_y * (ri->bits_per_channel / 8))) {
      PDI_FREE(out);
      return pdi__errpuc("bad PNM", "PNM file truncated");
   }

   if (req_comp && req_comp != s->img_n) {
      if (ri->bits_per_channel == 16) {
         out = (pdi_uc *) pdi__convert_format16((pdi__uint16 *) out, s->img_n, req_comp, s->img_x, s->img_y);
      } else {
         out = pdi__convert_format(out, s->img_n, req_comp, s->img_x, s->img_y);
      }
      if (out == NULL) return out; // pdi__convert_format frees input on failure
   }
   return out;
}

static int      pdi__pnm_isspace(char c)
{
   return c == ' ' || c == '\t' || c == '\n' || c == '\v' || c == '\f' || c == '\r';
}

static void     pdi__pnm_skip_whitespace(pdi__context *s, char *c)
{
   for (;;) {
      while (!pdi__at_eof(s) && pdi__pnm_isspace(*c))
         *c = (char) pdi__get8(s);

      if (pdi__at_eof(s) || *c != '#')
         break;

      while (!pdi__at_eof(s) && *c != '\n' && *c != '\r' )
         *c = (char) pdi__get8(s);
   }
}

static int      pdi__pnm_isdigit(char c)
{
   return c >= '0' && c <= '9';
}

static int      pdi__pnm_getinteger(pdi__context *s, char *c)
{
   int value = 0;

   while (!pdi__at_eof(s) && pdi__pnm_isdigit(*c)) {
      value = value*10 + (*c - '0');
      *c = (char) pdi__get8(s);
      if((value > 214748364) || (value == 214748364 && *c > '7'))
          return pdi__err("integer parse overflow", "Parsing an integer in the PPM header overflowed a 32-bit int");
   }

   return value;
}

static int      pdi__pnm_info(pdi__context *s, int *x, int *y, int *comp)
{
   int maxv, dummy;
   char c, p, t;

   if (!x) x = &dummy;
   if (!y) y = &dummy;
   if (!comp) comp = &dummy;

   pdi__rewind(s);

   // Get identifier
   p = (char) pdi__get8(s);
   t = (char) pdi__get8(s);
   if (p != 'P' || (t != '5' && t != '6')) {
       pdi__rewind(s);
       return 0;
   }

   *comp = (t == '6') ? 3 : 1;  // '5' is 1-component .pgm; '6' is 3-component .ppm

   c = (char) pdi__get8(s);
   pdi__pnm_skip_whitespace(s, &c);

   *x = pdi__pnm_getinteger(s, &c); // read width
   if(*x == 0)
       return pdi__err("invalid width", "PPM image header had zero or overflowing width");
   pdi__pnm_skip_whitespace(s, &c);

   *y = pdi__pnm_getinteger(s, &c); // read height
   if (*y == 0)
       return pdi__err("invalid width", "PPM image header had zero or overflowing width");
   pdi__pnm_skip_whitespace(s, &c);

   maxv = pdi__pnm_getinteger(s, &c);  // read max value
   if (maxv > 65535)
      return pdi__err("max value > 65535", "PPM image supports only 8-bit and 16-bit images");
   else if (maxv > 255)
      return 16;
   else
      return 8;
}

static int pdi__pnm_is16(pdi__context *s)
{
   if (pdi__pnm_info(s, NULL, NULL, NULL) == 16)
	   return 1;
   return 0;
}
#endif

static int pdi__info_main(pdi__context *s, int *x, int *y, int *comp)
{
   #ifndef PDI_NO_JPEG
   if (pdi__jpeg_info(s, x, y, comp)) return 1;
   #endif

   #ifndef PDI_NO_PNG
   if (pdi__png_info(s, x, y, comp))  return 1;
   #endif

   #ifndef PDI_NO_GIF
   if (pdi__gif_info(s, x, y, comp))  return 1;
   #endif

   #ifndef PDI_NO_BMP
   if (pdi__bmp_info(s, x, y, comp))  return 1;
   #endif

   #ifndef PDI_NO_PSD
   if (pdi__psd_info(s, x, y, comp))  return 1;
   #endif

   #ifndef PDI_NO_PIC
   if (pdi__pic_info(s, x, y, comp))  return 1;
   #endif

   #ifndef PDI_NO_PNM
   if (pdi__pnm_info(s, x, y, comp))  return 1;
   #endif

   #ifndef PDI_NO_HDR
   if (pdi__hdr_info(s, x, y, comp))  return 1;
   #endif

   // test tga last because it's a crappy test!
   #ifndef PDI_NO_TGA
   if (pdi__tga_info(s, x, y, comp))
       return 1;
   #endif
   return pdi__err("unknown image type", "Image not of any known type, or corrupt");
}

static int pdi__is_16_main(pdi__context *s)
{
   #ifndef PDI_NO_PNG
   if (pdi__png_is16(s))  return 1;
   #endif

   #ifndef PDI_NO_PSD
   if (pdi__psd_is16(s))  return 1;
   #endif

   #ifndef PDI_NO_PNM
   if (pdi__pnm_is16(s))  return 1;
   #endif
   return 0;
}

#ifndef PDI_NO_STDIO
PDIDEF int pdi_info(char const *filename, int *x, int *y, int *comp)
{
    FILE *f = pdi__fopen(filename, "rb");
    int result;
    if (!f) return pdi__err("can't fopen", "Unable to open file");
    result = pdi_info_from_file(f, x, y, comp);
    fclose(f);
    return result;
}

PDIDEF int pdi_info_from_file(FILE *f, int *x, int *y, int *comp)
{
   int r;
   pdi__context s;
   long pos = ftell(f);
   pdi__start_file(&s, f);
   r = pdi__info_main(&s,x,y,comp);
   fseek(f,pos,SEEK_SET);
   return r;
}

PDIDEF int pdi_is_16_bit(char const *filename)
{
    FILE *f = pdi__fopen(filename, "rb");
    int result;
    if (!f) return pdi__err("can't fopen", "Unable to open file");
    result = pdi_is_16_bit_from_file(f);
    fclose(f);
    return result;
}

PDIDEF int pdi_is_16_bit_from_file(FILE *f)
{
   int r;
   pdi__context s;
   long pos = ftell(f);
   pdi__start_file(&s, f);
   r = pdi__is_16_main(&s);
   fseek(f,pos,SEEK_SET);
   return r;
}
#endif // !PDI_NO_STDIO

PDIDEF int pdi_info_from_memory(pdi_uc const *buffer, int len, int *x, int *y, int *comp)
{
   pdi__context s;
   pdi__start_mem(&s,buffer,len);
   return pdi__info_main(&s,x,y,comp);
}

PDIDEF int pdi_info_from_callbacks(pdi_io_callbacks const *c, void *user, int *x, int *y, int *comp)
{
   pdi__context s;
   pdi__start_callbacks(&s, (pdi_io_callbacks *) c, user);
   return pdi__info_main(&s,x,y,comp);
}

PDIDEF int pdi_is_16_bit_from_memory(pdi_uc const *buffer, int len)
{
   pdi__context s;
   pdi__start_mem(&s,buffer,len);
   return pdi__is_16_main(&s);
}

PDIDEF int pdi_is_16_bit_from_callbacks(pdi_io_callbacks const *c, void *user)
{
   pdi__context s;
   pdi__start_callbacks(&s, (pdi_io_callbacks *) c, user);
   return pdi__is_16_main(&s);
}

#endif // PD_IMAGE_IMPLEMENTATION

/*
   revision history:
      2.20  (2019-02-07) support utf8 filenames in Windows; fix warnings and platform ifdefs
      2.19  (2018-02-11) fix warning
      2.18  (2018-01-30) fix warnings
      2.17  (2018-01-29) change sbti__shiftsigned to avoid clang -O2 bug
                         1-bit BMP
                         *_is_16_bit api
                         avoid warnings
      2.16  (2017-07-23) all functions have 16-bit variants;
                         PDI_NO_STDIO works again;
                         compilation fixes;
                         fix rounding in unpremultiply;
                         optimize vertical flip;
                         disable raw_len validation;
                         documentation fixes
      2.15  (2017-03-18) fix png-1,2,4 bug; now all Imagenet JPGs decode;
                         warning fixes; disable run-time SSE detection on gcc;
                         uniform handling of optional "return" values;
                         thread-safe initialization of zlib tables
      2.14  (2017-03-03) remove deprecated PDI_JPEG_OLD; fixes for Imagenet JPGs
      2.13  (2016-11-29) add 16-bit API, only supported for PNG right now
      2.12  (2016-04-02) fix typo in 2.11 PSD fix that caused crashes
      2.11  (2016-04-02) allocate large structures on the stack
                         remove white matting for transparent PSD
                         fix reported channel count for PNG & BMP
                         re-enable SSE2 in non-gcc 64-bit
                         support RGB-formatted JPEG
                         read 16-bit PNGs (only as 8-bit)
      2.10  (2016-01-22) avoid warning introduced in 2.09 by PDI_REALLOC_SIZED
      2.09  (2016-01-16) allow comments in PNM files
                         16-bit-per-pixel TGA (not bit-per-component)
                         info() for TGA could break due to .hdr handling
                         info() for BMP to shares code instead of sloppy parse
                         can use PDI_REALLOC_SIZED if allocator doesn't support realloc
                         code cleanup
      2.08  (2015-09-13) fix to 2.07 cleanup, reading RGB PSD as RGBA
      2.07  (2015-09-13) fix compiler warnings
                         partial animated GIF support
                         limited 16-bpc PSD support
                         #ifdef unused functions
                         bug with < 92 byte PIC,PNM,HDR,TGA
      2.06  (2015-04-19) fix bug where PSD returns wrong '*comp' value
      2.05  (2015-04-19) fix bug in progressive JPEG handling, fix warning
      2.04  (2015-04-15) try to re-enable SIMD on MinGW 64-bit
      2.03  (2015-04-12) extra corruption checking (mmozeiko)
                         pdi_set_flip_vertically_on_load (nguillemot)
                         fix NEON support; fix mingw support
      2.02  (2015-01-19) fix incorrect assert, fix warning
      2.01  (2015-01-17) fix various warnings; suppress SIMD on gcc 32-bit without -msse2
      2.00b (2014-12-25) fix PDI_MALLOC in progressive JPEG
      2.00  (2014-12-25) optimize JPG, including x86 SSE2 & NEON SIMD (ryg)
                         progressive JPEG (stb)
                         PGM/PPM support (Ken Miller)
                         PDI_MALLOC,PDI_REALLOC,PDI_FREE
                         GIF bugfix -- seemingly never worked
                         PDI_NO_*, PDI_ONLY_*
      1.48  (2014-12-14) fix incorrectly-named assert()
      1.47  (2014-12-14) 1/2/4-bit PNG support, both direct and paletted (Omar Cornut & stb)
                         optimize PNG (ryg)
                         fix bug in interlaced PNG with user-specified channel count (stb)
      1.46  (2014-08-26)
              fix broken tRNS chunk (colorkey-style transparency) in non-paletted PNG
      1.45  (2014-08-16)
              fix MSVC-ARM internal compiler error by wrapping malloc
      1.44  (2014-08-07)
              various warning fixes from Ronny Chevalier
      1.43  (2014-07-15)
              fix MSVC-only compiler problem in code changed in 1.42
      1.42  (2014-07-09)
              don't define _CRT_SECURE_NO_WARNINGS (affects user code)
              fixes to pdi__cleanup_jpeg path
              added PDI_ASSERT to avoid requiring assert.h
      1.41  (2014-06-25)
              fix search&replace from 1.36 that messed up comments/error messages
      1.40  (2014-06-22)
              fix gcc struct-initialization warning
      1.39  (2014-06-15)
              fix to TGA optimization when req_comp != number of components in TGA;
              fix to GIF loading because BMP wasn't rewinding (whoops, no GIFs in my test suite)
              add support for BMP version 5 (more ignored fields)
      1.38  (2014-06-06)
              suppress MSVC warnings on integer casts truncating values
              fix accidental rename of 'skip' field of I/O
      1.37  (2014-06-04)
              remove duplicate typedef
      1.36  (2014-06-03)
              convert to header file single-file library
              if de-iphone isn't set, load iphone images color-swapped instead of returning NULL
      1.35  (2014-05-27)
              various warnings
              fix broken PDI_SIMD path
              fix bug where pdi_load_from_file no longer left file pointer in correct place
              fix broken non-easy path for 32-bit BMP (possibly never used)
              TGA optimization by Arseny Kapoulkine
      1.34  (unknown)
              use PDI_NOTUSED in pdi__resample_row_generic(), fix one more leak in tga failure case
      1.33  (2011-07-14)
              make pdi_is_hdr work in PDI_NO_HDR (as specified), minor compiler-friendly improvements
      1.32  (2011-07-13)
              support for "info" function for all supported filetypes (SpartanJ)
      1.31  (2011-06-20)
              a few more leak fixes, bug in PNG handling (SpartanJ)
      1.30  (2011-06-11)
              added ability to load files via callbacks to accomidate custom input streams (Ben Wenger)
              removed deprecated format-specific test/load functions
              removed support for installable file formats (pdi_loader) -- would have been broken for IO callbacks anyway
              error cases in bmp and tga give messages and don't leak (Raymond Barbiero, grisha)
              fix inefficiency in decoding 32-bit BMP (David Woo)
      1.29  (2010-08-16)
              various warning fixes from Aurelien Pocheville
      1.28  (2010-08-01)
              fix bug in GIF palette transparency (SpartanJ)
      1.27  (2010-08-01)
              cast-to-pdi_uc to fix warnings
      1.26  (2010-07-24)
              fix bug in file buffering for PNG reported by SpartanJ
      1.25  (2010-07-17)
              refix trans_data warning (Won Chun)
      1.24  (2010-07-12)
              perf improvements reading from files on platforms with lock-heavy fgetc()
              minor perf improvements for jpeg
              deprecated type-specific functions so we'll get feedback if they're needed
              attempt to fix trans_data warning (Won Chun)
      1.23    fixed bug in iPhone support
      1.22  (2010-07-10)
              removed image *writing* support
              pdi_info support from Jetro Lauha
              GIF support from Jean-Marc Lienher
              iPhone PNG-extensions from James Brown
              warning-fixes from Nicolas Schulz and Janez Zemva (i.pdi__err. Janez (U+017D)emva)
      1.21    fix use of 'pdi_uc' in header (reported by jon blow)
      1.20    added support for Softimage PIC, by Tom Seddon
      1.19    bug in interlaced PNG corruption check (found by ryg)
      1.18  (2008-08-02)
              fix a threading bug (local mutable static)
      1.17    support interlaced PNG
      1.16    major bugfix - pdi__convert_format converted one too many pixels
      1.15    initialize some fields for thread safety
      1.14    fix threadsafe conversion bug
              header-file-only version (#define PDI_HEADER_FILE_ONLY before including)
      1.13    threadsafe
      1.12    const qualifiers in the API
      1.11    Support installable IDCT, colorspace conversion routines
      1.10    Fixes for 64-bit (don't use "unsigned long")
              optimized upsampling by Fabian "ryg" Giesen
      1.09    Fix format-conversion for PSD code (bad global variables!)
      1.08    Thatcher Ulrich's PSD code integrated by Nicolas Schulz
      1.07    attempt to fix C++ warning/errors again
      1.06    attempt to fix C++ warning/errors again
      1.05    fix TGA loading to return correct *comp and use good luminance calc
      1.04    default float alpha is 1, not 255; use 'void *' for pdi_image_free
      1.03    bugfixes to PDI_NO_STDIO, PDI_NO_HDR
      1.02    support for (subset of) HDR files, float interface for preferred access to them
      1.01    fix bug: possible bug in handling right-side up bmps... not sure
              fix bug: the pdi__bmp_load() and pdi__tga_load() functions didn't work at all
      1.00    interface to zlib that skips zlib header
      0.99    correct handling of alpha in palette
      0.98    TGA loader by lonesock; dynamically add loaders (untested)
      0.97    jpeg errors on too large a file; also catch another malloc failure
      0.96    fix detection of invalid v value - particleman@mollyrocket forum
      0.95    during header scan, seek to markers in case of padding
      0.94    PDI_NO_STDIO to disable stdio usage; rename all #defines the same
      0.93    handle jpegtran output; verbose errors
      0.92    read 4,8,16,24,32-bit BMP files of several formats
      0.91    output 24-bit Windows 3.0 BMP files
      0.90    fix a few more warnings; bump version number to approach 1.0
      0.61    bugfixes due to Marc LeBlanc, Christopher Lloyd
      0.60    fix compiling as c++
      0.59    fix warnings: merge Dave Moore's -Wall fixes
      0.58    fix bug: zlib uncompressed mode len/nlen was wrong endian
      0.57    fix bug: jpg last huffman symbol before marker was >9 bits but less than 16 available
      0.56    fix bug: zlib uncompressed mode len vs. nlen
      0.55    fix bug: restart_interval not initialized to 0
      0.54    allow NULL for 'int *comp'
      0.53    fix bug in png 3->4; speedup png decoding
      0.52    png handles req_comp=3,4 directly; minor cleanup; jpeg comments
      0.51    obey req_comp requests, 1-component jpegs return as 1-component,
              on 'test' only check type, not whether we support this variant
      0.50  (2006-11-19)
              first released version
*/


/*
------------------------------------------------------------------------------
This software is available under 2 licenses -- choose whichever you prefer.
------------------------------------------------------------------------------
ALTERNATIVE A - MIT License
Copyright (c) 2017 Sean Barrett
Permission is hereby granted, free of charge, to any person obtaining a copy of
this software and associated documentation files (the "Software"), to deal in
the Software without restriction, including without limitation the rights to
use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
of the Software, and to permit persons to whom the Software is furnished to do
so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
------------------------------------------------------------------------------
ALTERNATIVE B - Public Domain (www.unlicense.org)
This is free and unencumbered software released into the public domain.
Anyone is free to copy, modify, publish, use, compile, sell, or distribute this
software, either in source code form or as a compiled binary, for any purpose,
commercial or non-commercial, and by any means.
In jurisdictions that recognize copyright laws, the author or authors of this
software dedicate any and all copyright interest in the software to the public
domain. We make this dedication for the benefit of the public at large and to
the detriment of our heirs and successors. We intend this dedication to be an
overt act of relinquishment in perpetuity of all present and future rights to
this software under copyright law.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
------------------------------------------------------------------------------
*/