public static void process(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;

		//CONCURRENT_BELOW BoofConcurrency.loopFor(1,height,y->{
		for (int y = 1; y < height; y++) {
			int endX = width * y + width - 1;

			for (int index = width * y + 1; 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 });
	}
public static void process ( 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 ; for ( int y = 1 ; y < height ; y ++ ) { int endX = width * y + width - 1 ; for ( int index = width * y + 1 ; 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 ) ; } } }
Computes derivative of GrayU8.  None of the images can be sub-images.