static IBWImage iBWImageFromFunction(IF2_IntInt_Double f, int w, int h) {
  ret new IBWImage {
    public int getWidth() { ret w; }
    public int getHeight() { ret h; }
    
    public float getFloatPixel(int x, int y) {
      ret (float) f.get(x, y);
    }
  };
}