code: public static double computeWeightedError(GrayF32 imgA, GrayF32 imgB ,
  											  GrayF32 imgWeight ) {
  		final int h = imgA.getHeight();
  		final int w = imgA.getWidth();
  
  		double total = 0;
  		double totalWeight = 0;
  
  		for (int y = 0; y < h; y++) {
  			for (int x = 0; x < w; x++) {
  				float weight = imgWeight.get(x,y);
  				double difference =  Math.abs(imgA.get(x,y)-imgB.get(x,y));
  				total += difference*weight;
  				totalWeight += weight;
  			}
  		}
  
  		return total / totalWeight;
  	}
docs: todo push to what ops?