Function lodepng_convert

depends/lodepng/lodepng.cpp:3524–3596

}

unsigned lodepng_convert(unsigned char* out, const unsigned char* in,
                         const LodePNGColorMode* mode_out, const LodePNGColorMode* mode_in,
                         unsigned w, unsigned h) {
  size_t i;
  ColorTree tree;
  size_t numpixels = (size_t)w * (size_t)h;
  unsigned error = 0;

  if(mode_in->colortype == LCT_PALETTE && !mode_in->palette) {
    return 107; /* error: must provide palette if input mode is palette */
  }

  if(lodepng_color_mode_equal(mode_out, mode_in)) {
    size_t numbytes = lodepng_get_raw_size(w, h, mode_in);
    lodepng_memcpy(out, in, numbytes);
    return 0;
  }

  if(mode_out->colortype == LCT_PALETTE) {
    size_t palettesize = mode_out->palettesize;
    const unsigned char* palette = mode_out->palette;
    size_t palsize = (size_t)1u << mode_out->bitdepth;
    /*if the user specified output palette but did not give the values, assume
    they want the values of the input color type (assuming that one is palette).
    Note that we never create a new palette ourselves.*/
    if(palettesize == 0) {
      palettesize = mode_in->palettesize;
      palette = mode_in->palette;
      /*if the input was also palette with same bitdepth, then the color types are also
      equal, so copy literally. This to preserve the exact indices that were in the PNG
      even in case there are duplicate colors in the palette.*/
      if(mode_in->colortype == LCT_PALETTE && mode_in->bitdepth == mode_out->bitdepth) {
        size_t numbytes = lodepng_get_raw_size(w, h, mode_in);
        lodepng_memcpy(out, in, numbytes);
        return 0;
      }
    }
    if(palettesize < palsize) palsize = palettesize;
    color_tree_init(&tree);
    for(i = 0; i != palsize; ++i) {
      const unsigned char* p = &palette[i * 4];
      error = color_tree_add(&tree, p[0], p[1], p[2], p[3], (unsigned)i);
      if(error) break;
    }
  }

  if(!error) {
    if(mode_in->bitdepth == 16 && mode_out->bitdepth == 16) {
      for(i = 0; i != numpixels; ++i) {
        unsigned short r = 0, g = 0, b = 0, a = 0;
        getPixelColorRGBA16(&r, &g, &b, &a, in, i, mode_in);
        rgba16ToPixel(out, i, mode_out, r, g, b, a);
      }
    } else if(mode_out->bitdepth == 8 && mode_out->colortype == LCT_RGBA) {
      getPixelColorsRGBA8(out, numpixels, in, mode_in);
    } else if(mode_out->bitdepth == 8 && mode_out->colortype == LCT_RGB) {
      getPixelColorsRGB8(out, numpixels, in, mode_in);
    } else {