static Matrix<Int> imageToMatrix(BufferedImage etc img) {
  if (img == null) null;
  int _w = img.getWidth(), _h = img.getHeight();
  
  class ImageToMatrix extends AbstractMatrix<Int> {
    *() { super(_w, _h); }
    
    public Int get(int x, int y) {
      assertPointInBounds(x, y, w, h);
      ret img.getRGB(x, y);
    }
    
    public void set(int x, int y, Int val) {
      assertPointInBounds(x, y, w, h);
      img.setRGB(x, y, val);
    }
  };
  
  ret new ImageToMatrix;
}