static bool imagesIdentical_slow(BufferedImage img1, BufferedImage img2) {
  if (img1 == null) ret img2 == null;
  if (img2 == null) false;
  int w = img1.getWidth(), h = img1.getHeight();
  if (w != img2.getWidth() || h != img2.getHeight()) false;
  for y to h: for x to w:
    if (img1.getRGB(x, y) != img2.getRGB(x, y)) false;
  true;
}