docs: public static void localHistogram( GrayU16 input , int x0 , int y0 , int x1, int y1 , int histogram[] ) {
  		for( int i = 0; i < histogram.length; i++ )
  			histogram[i] = 0;
  
  		for( int i = y0; i < y1; i++ ) {
  			int index = input.startIndex + i*input.stride + x0;
  			int end = index + x1-x0;
  			for( ; index < end; index++ ) {
  				histogram[input.data[index] & 0xFFFF]++;
  			}
  		}
  	}