static IIntegralImage iiPad(IIntegralImage inner, int w, int h, int innerX1, int innerY1) {
  int[] padColor = {0, 0, 0}; // black
  IIntegralImage img = inner;
  
  // add top border
  if (innerY1 > 0)
    img = IIVerticalSplit(IISingleColor(img.getWidth(), innerY1, padColor), img);
  
  // add bottom border
  if (img.getHeight() < h)
    img = IIVerticalSplit(img, IISingleColor(img.getWidth(), h-img.getHeight(), padColor));
    
  // add left border
  if (innerX1 > 0)
    img = IIHorizontalSplit(IISingleColor(innerX1, img.getHeight(), padColor), img);
  
  // add right border
  if (img.getWidth() < w)
    img = IIHorizontalSplit(img, IISingleColor(w-img.getWidth(), img.getHeight(), padColor));
    
  ret img;
}