Function rgba8ToPixel

samples/shared/lodepng.cpp:3017–3088

put a pixel, given its RGBA color, into image of any color type*/

/*put a pixel, given its RGBA color, into image of any color type*/
static unsigned rgba8ToPixel(unsigned char* out, size_t i,
                             const LodePNGColorMode* mode, ColorTree* tree /*for palette*/,
                             unsigned char r, unsigned char g, unsigned char b, unsigned char a)
{
  if(mode->colortype == LCT_GREY)
  {
    unsigned char grey = r; /*((unsigned short)r + g + b) / 3*/;
    if(mode->bitdepth == 8) out[i] = grey;
    else if(mode->bitdepth == 16) out[i * 2 + 0] = out[i * 2 + 1] = grey;
    else
    {
      /*take the most significant bits of grey*/
      grey = (grey >> (8 - mode->bitdepth)) & ((1 << mode->bitdepth) - 1);
      addColorBits(out, i, mode->bitdepth, grey);
    }
  }
  else if(mode->colortype == LCT_RGB)
  {
    if(mode->bitdepth == 8)
    {
      out[i * 3 + 0] = r;
      out[i * 3 + 1] = g;
      out[i * 3 + 2] = b;
    }
    else
    {
      out[i * 6 + 0] = out[i * 6 + 1] = r;
      out[i * 6 + 2] = out[i * 6 + 3] = g;
      out[i * 6 + 4] = out[i * 6 + 5] = b;
    }
  }
  else if(mode->colortype == LCT_PALETTE)
  {
    int index = color_tree_get(tree, r, g, b, a);
    if(index < 0) return 82; /*color not in palette*/
    if(mode->bitdepth == 8) out[i] = index;
    else addColorBits(out, i, mode->bitdepth, (unsigned)index);
  }
  else if(mode->colortype == LCT_GREY_ALPHA)
  {
    unsigned char grey = r; /*((unsigned short)r + g + b) / 3*/;
    if(mode->bitdepth == 8)
    {
      out[i * 2 + 0] = grey;
      out[i * 2 + 1] = a;
    }
    else if(mode->bitdepth == 16)
    {
      out[i * 4 + 0] = out[i * 4 + 1] = grey;
      out[i * 4 + 2] = out[i * 4 + 3] = a;
    }
  }
  else if(mode->colortype == LCT_RGBA)
  {
    if(mode->bitdepth == 8)
    {
      out[i * 4 + 0] = r;
      out[i * 4 + 1] = g;