static BufferedImage renderImageOnBackground(Color bg, BufferedImage img) {
  if (img == null) null;
  BufferedImage canvas = newBufferedImage(img.getWidth(), img.getHeight(), bg);
  drawImageOnImage(img, canvas);
  ret canvas;
}

static BufferedImage renderImageOnBackground(BufferedImage img, Color bg) {
  ret renderImageOnBackground(bg, img);
}