static int colorCount332_max(int max, BufferedImage img) {
  if (max == 0) ret 0;
  int w = img.getWidth(), h = img.getHeight(), n = 0;
  new BitSet bs;
  for y to h: for x to w: {
    int idx = ubyteToInt(to332(img.getRGB(x, y)));
    if (!bs.get(idx)) {
      if (++n >= max) ret n;
      setBit(bs, idx);
    }
  }
  ret n;
}