static void addColorBits(unsigned char* out, size_t index, unsigned bits, unsigned in)
{
  unsigned m = bits == 1 ? 7 : bits == 2 ? 3 : 1; /*8 / bits - 1*/
  /*p = the partial index in the byte, e.g. with 4 palettebits it is 0 for first half or 1 for second half*/
  unsigned p = index & m;
  in &= (1u << bits) - 1u; /*filter out any other bits of the input value*/
  in = in << (bits * (m - p));
  if(p == 0) out[index * bits / 8] = in;
  else out[index * bits / 8] |= in;
}
Unknown