static IBWIntegralImage scaledIBWIntegralImage(BWIntegralImage img, int w, int h) {
  ret new IBWIntegralImage {
    int w1 = img.w, h1 = img.h;
    
    public int getWidth() { ret w; }
    public int getHeight() { ret h; }
    
    public double getPixelAverage(int x1, int y1, int x2, int y2) {
      int _x1 = x1*w1/w, _x2 = x2*w1/w;
      int _y1 = y1*h1/h, _y2 = y2*h1/h;
      ret img.getPixelAverage(_x1, _y1, _x2, _y2);
    }
  };
}