static BufferedImage renderTiledBackground(S tileImageID, int w, int h) {
  ret renderTiledBackground(tileImageID, w, h, 0, 0);
}

static BufferedImage renderTiledBackground(S tileImageID, int w, int h, int shiftX, int shiftY) {
  BufferedImage tileImage = loadImage2(tileImageID);
  BufferedImage img = newBufferedImage(w, h, Color.black);
  Graphics2D g = img.createGraphics();
  int tw = tileImage.getWidth(), th = tileImage.getHeight();
  for (int x = mod(shiftX-1, tw)-tw+1; x < w; x += tw)
    for (int y = mod(shiftY-1, th)-th+1; y < h; y += th)
      g.drawImage(tileImage, x, y, null);  
  g.dispose();
  ret img;
}