110 lines
3.5 KiB
C++
110 lines
3.5 KiB
C++
#include <renderd7/bmpconverter.hpp>
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namespace BitmapConverter {
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// returns 0 if all went ok, non-0 if error
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// output image is always given in RGBA (with alpha channel), even if it's a BMP
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// without alpha channel
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unsigned decodeBMP(std::vector<unsigned char> &image, unsigned &w, unsigned &h,
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const std::vector<unsigned char> &bmp) {
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static const unsigned MINHEADER = 54; // minimum BMP header size
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if (bmp.size() < MINHEADER)
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return -1;
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if (bmp[0] != 'B' || bmp[1] != 'M')
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return 1; // It's not a BMP file if it doesn't start with marker 'BM'
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unsigned pixeloffset = bmp[10] + 256 * bmp[11]; // where the pixel data starts
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// read width and height from BMP header
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w = bmp[18] + bmp[19] * 256;
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h = bmp[22] + bmp[23] * 256;
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// read number of channels from BMP header
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if (bmp[28] != 24 && bmp[28] != 32)
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return 2; // only 24-bit and 32-bit BMPs are supported.
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unsigned numChannels = bmp[28] / 8;
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// The amount of scanline bytes is width of image times channels, with extra
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// bytes added if needed to make it a multiple of 4 bytes.
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unsigned scanlineBytes = w * numChannels;
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if (scanlineBytes % 4 != 0)
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scanlineBytes = (scanlineBytes / 4) * 4 + 4;
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unsigned dataSize = scanlineBytes * h;
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if (bmp.size() < dataSize + pixeloffset)
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return 3; // BMP file too small to contain all pixels
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image.resize(w * h * 4);
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/*
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There are 3 differences between BMP and the raw image buffer for LodePNG:
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-it's upside down
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-it's in BGR instead of RGB format (or BRGA instead of RGBA)
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-each scanline has padding bytes to make it a multiple of 4 if needed
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The 2D for loop below does all these 3 conversions at once.
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*/
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for (unsigned y = 0; y < h; y++)
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for (unsigned x = 0; x < w; x++) {
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// pixel start byte position in the BMP
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unsigned bmpos =
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pixeloffset + (h - y - 1) * scanlineBytes + numChannels * x;
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// pixel start byte position in the new raw image
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unsigned newpos = 4 * y * w + 4 * x;
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if (numChannels == 3) {
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image[newpos + 0] = bmp[bmpos + 2]; // R
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image[newpos + 1] = bmp[bmpos + 1]; // G
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image[newpos + 2] = bmp[bmpos + 0]; // B
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image[newpos + 3] = 255; // A
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} else {
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image[newpos + 0] = bmp[bmpos + 2]; // R
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image[newpos + 1] = bmp[bmpos + 1]; // G
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image[newpos + 2] = bmp[bmpos + 0]; // B
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image[newpos + 3] = bmp[bmpos + 3]; // A
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}
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}
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return 0;
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}
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std::vector<unsigned char> ConvertFile(std::string filename) {
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std::vector<unsigned char> bmp;
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lodepng::load_file(bmp, filename);
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std::vector<unsigned char> image;
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unsigned w, h;
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unsigned error = BitmapConverter::decodeBMP(image, w, h, bmp);
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if (error) {
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std::cout << "BMP decoding error " << error << std::endl;
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}
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std::vector<unsigned char> png;
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error = lodepng::encode(png, image, w, h);
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if (error) {
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std::cout << "PNG encoding error " << error << ": "
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<< lodepng_error_text(error) << std::endl;
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}
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return png;
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}
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std::vector<unsigned char> ConvertData(std::vector<unsigned char> data) {
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std::vector<unsigned char> image;
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unsigned w, h;
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unsigned error = BitmapConverter::decodeBMP(image, w, h, data);
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if (error) {
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std::cout << "BMP decoding error " << error << std::endl;
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}
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std::vector<unsigned char> png;
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error = lodepng::encode(png, image, w, h);
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if (error) {
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std::cout << "PNG encoding error " << error << ": "
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<< lodepng_error_text(error) << std::endl;
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}
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return png;
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}
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} // namespace BitmapConverter
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