Function paethPredictor

samples/shared/lodepng.cpp:3737–3746

Paeth predicter, used by PNG filter type 4 The parameters are of type short, but should come from unsigned chars, the shorts are only needed to make the paeth calculation correct. */

are only needed to make the paeth calculation correct.
*/
static unsigned char paethPredictor(short a, short b, short c)
{
  short pa = abs(b - c);
  short pb = abs(a - c);
  short pc = abs(a + b - c - c);

  if(pc < pa && pc < pb) return (unsigned char)c;
  else if(pb < pa) return (unsigned char)b;
  else return (unsigned char)a;
}

/*shared values used by multiple Adam7 related functions*/