static BufferedImage cutOutPixelSet(BufferedImage image, PixelSet set) {
  Rect r = pixelSetBounds(set);
  BufferedImage img = transparentBufferedImage(r.w, r.h);
  for (Pixel p : set)
    img.setRGB(p.x-r.x, p.y-r.y, image.getRGB(p.x, p.y));
  ret img;
}