static BufferedImage renderRenderable(int w, int h, Renderable r) {
  BufferedImage img = newBufferedImage(w, h);
  r?.renderOn(imageGraphics(img), w, h);
  ret img;
}

// modifies original image
static BufferedImage renderRenderable(BufferedImage img, Renderable r) {
  r?.renderOn(imageGraphics(img), img.getWidth(), img.getHeight());
  ret img;
}