static IIntegralImage scaledIntegralImage(IIntegralImage img, int w) {
  ret scaledIntegralImage(img, w, iround(w*img.getHeight()/(double) img.getWidth()));
}

static IIntegralImage scaledIntegralImage(IIntegralImage img, int w, int h) {
  ret new IIntegralImage {
    int w1 = img.getWidth(), h1 = img.getHeight();
    double factorX = doubleRatio(w1, w);
    double factorY = doubleRatio(h1, h);
    double areaCorrection = 1/(factorX*factorY);
    
    public int getWidth() { ret w; }
    public int getHeight() { ret h; }
    
    // get value for 1 channel
    // normal range [0; pixelCount*256)
    // TODO: test
    public double getIntegralValue(int x, int y, int channel) {
      ret img.getIntegralValue(x*factorX, y*factorY, channel)*areaCorrection;
    }
  };
}