static RGBImage rgbVisualizeRectsZoomed(RGBImage img, L<Rect> rects) {
  int w = img.w(), h = img.h();
  RGBImage img2 = new RGBImage(w*2, h*2);
  for y to h: for x to w: {
    int color = img.getInt(x, y);
    img2.setPixel(x*2, y*2, color);
    img2.setPixel(x*2, y*2+1, color);
    img2.setPixel(x*2+1, y*2+1, color);
    img2.setPixel(x*2+1, y*2+1, color);
  }
  for (Rect r : rects) {
    int y2 = min(r.x);
    rgbDrawRect(r.w
  }
  ret img2;
}