Harris Corner Detection Kernel

									uchar4 __attribute__((kernel)) harris(const uchar4 in, uint32_t x, uint32_t y)
	{
	    float c = 0.04;

	    float4 convXpixel = rsUnpackColor8888(rsGetElementAt_uchar4(convX, x, y));
	    float4 convYpixel = rsUnpackColor8888(rsGetElementAt_uchar4(convY, x, y));

	    float Ix = convXpixel.r * gMonoMult[0] + convXpixel.g * gMonoMult[1] +
			convXpixel.b * gMonoMult[2];
	    float Iy = convYpixel.r * gMonoMult[0] + convYpixel.g * gMonoMult[1] +
			convYpixel.b * gMonoMult[2];
	    float Ixx = Ix * Ix;
	    float Iyy = Iy * Iy;
	    float Ixy = Ix * Iy;

	    float cornerResponse = (Ixx*Iyy - Ixy*Ixy - c*(Ixx+Iyy)*(Ixx+Iyy));
	    if(cornerResponse < harrisThreshold ) {
	        cornerColorRGB.r = 0;
	        cornerColorRGB.g = 255;
	        cornerColorRGB.b = 0;
	        return cornerColorRGB;
	    } else {
	        return in;
	    }
	}