static MultiSet<S> histogram332(RGBImage img) {
  int[] a = histogram332_array(img);
  new MultiSet<S> histogram;
  for i over a: {
    int x = a[i];
    if (x != 0)
      histogram.add(byte332ToString(i), x);
  }
  ret histogram;
}

static MultiSet<S> histogram332(BufferedImage img) {
  ret histogram332(RGBImage(img));
}