static double saturationFromRGB(int rgb) {
  int r = (rgb >> 16) & 0xFF;
  int g = (rgb >> 8) & 0xFF;
  int b = rgb & 0xFF;
  int min = min(min(r, g), b);
  int max = max(max(r, g), b);
  ret max != 0 ? (max-min) / (double) max : 0;
}