docs: public static void process_I8(GrayU8 orig,
  								  GrayS16 derivX,
  								  GrayS16 derivY) {
  		final byte[] data = orig.data;
  		final short[] imgX = derivX.data;
  		final short[] imgY = derivY.data;
  
  		final int width = orig.getWidth();
  		final int height = orig.getHeight() - 1;
  
  		final int adjWidth = width - 2;
  
  		//CONCURRENT_BELOW BoofConcurrency.loopFor(1,height,y->{
  		for (int y = 1; y < height; y++) {
  			int endX_alt = width * y + (width - adjWidth % 3) - 1;
  			int endX = endX_alt + adjWidth % 3;
  
  			int a11, a12, a13;
  			int a21, a22, a23;
  			int a31, a32, a33;
  
  			int index = width * y + 1;
  
  			a11 = data[index - width - 1] & 0xFF;
  			a12 = data[index - width] & 0xFF;
  			a21 = data[index - 1] & 0xFF;
  			a22 = data[index] & 0xFF;
  			a31 = data[index + width - 1] & 0xFF;
  			a32 = data[index + width] & 0xFF;
  
  			for (; index < endX_alt;) {
  				a13 = data[index - width + 1] & 0xFF;
  				a23 = data[index + 1] & 0xFF;
  				a33 = data[index + width + 1] & 0xFF;
  
  				int v = (a33 - a11);
  				int w = (a31 - a13);
  
  				imgY[index] = (short) ((a32 - a12) * 2 + v + w);
  				imgX[index] = (short) ((a23 - a21) * 2 + v - w);
  
  				index++;
  
  				a11 = data[index - width + 1] & 0xFF;
  				a21 = data[index + 1] & 0xFF;
  				a31 = data[index + width + 1] & 0xFF;
  
  				v = (a31 - a12);
  				w = (a32 - a11);
  
  				imgY[index] = (short) ((a33 - a13) * 2 + v + w);
  				imgX[index] = (short) ((a21 - a22) * 2 + v - w);
  
  				index++;
  
  				a12 = data[index - width + 1] & 0xFF;
  				a22 = data[index + 1] & 0xFF;
  				a32 = data[index + width + 1] & 0xFF;
  
  				v = (a32 - a13);
  				w = (a33 - a12);
  
  				imgY[index] = (short) ((a31 - a11) * 2 + v + w);
  				imgX[index] = (short) ((a22 - a23) * 2 + v - w);
  
  				index++;
  			}
  
  			for (; index < endX; index++) {
  				int v = (data[index + width + 1] & 0xFF) - (data[index - width - 1] & 0xFF);
  				int w = (data[index + width - 1] & 0xFF) - (data[index - width + 1] & 0xFF);
  
  				imgY[index] = (short) (((data[index + width] & 0xFF) - (data[index - width] & 0xFF)) * 2 + v + w);
  
  				imgX[index] = (short) (((data[index + 1] & 0xFF) - (data[index - 1] & 0xFF)) * 2 + v - w);
  			}
  		}
  		//CONCURRENT_ABOVE });
  	}