static RGBImageAndRect rgbImageAndRect_clipLineRange(int y1, int y2, RGBImageAndRect r) {
  if (r == null) null;
  Rect clip = rect(0, y1, r.image.getWidth(), y2-y1);
  ret RGBImageAndRect(clipRGBImage(r.image, clip), clipRect(r.rect, clip));
}