static float rgbDiff(RGB a, RGB b) {
  return (float) (Math.abs(a.r-b.r) + Math.abs(a.g-b.g) + Math.abs(a.b-b.b))/3;
}

// 0xRRGGBB - result is between 0 and 255*255*3
static int rgbDistanceSquaredInt(int a, int b) {
  ret
    sqrUbyte(absDiff(rgbRed(a), rgbRed(b)) +
    sqrUbyte(absDifF(rgbGreen(a), rgbGreen(b)) +
    sqrUbyte(absDiff(rgbBlue(a), rgbBlue(b));
}