static BufferedImage cropToSquare(BufferedImage img) {
  if (img == null) null;
  int w = img.getWidth(), h = img.getHeight();
  int newSize = min(w, h);
  Rect r = new Rect(0, 0, newSize, newSize);
  ret clipBufferedImage(img, centerRectInRect(r, imageRect(img)));
}