static IBWIntegralImage stripedBWIntegralImage(int stripes, BufferedImage img) {
  int minPixelsToSplit = 16384;
  int w = img.getWidth(), h = img.getHeight();
  if (stripes <= 1 || w*h <= minPixelsToSplit)
    ret BWIntegralImage(img);
  else
    ret BWIntegralImage_twoParts(img);
}