differentialFilter.cpp

Mat applyFilter(Mat &gray_1, Mat &kernal){
	
  	Point anchor = Point (-1,1);
  	double delta = 0;
  	int ddepth = -1;
  
  	Mat temp; // temporarily store the image
  	Mat gray; // final grayscale image after differentiation
  
  	// Apply the differential filter
  	filter2D(gray_1, temp, ddepth, kernal, anchor, delta, BORDER_DEFAULT);
  	
  	// Raise to the square
  	pow(temp, 2, gray);
  	
  	return gray;
}

vector<Mat> applyFilter(Mat &color){
	Mat temp;
	Mat gray;
	vector<Mat> result;

	// Convert the picture into Grayscale
	cvtColor (color, gray, CV_RGB2GRAY);

  // Kernal for horizontal differentiation
	Mat hor_kernal = (Mat_<double>(3,3) << 1, 0, -1, 2, 0, -2, 1, 0, -1);
	result.push_back(applyFilter(gray, hor_kernal));
	
	// Kernal for vertical differentiaiton
	Mat ver_kernal = (Mat_<double>(3,3) << 1, 2, 1, 0, 0, 0, -1, -2, -1);
	result.push_back(applyFilter(gray, ver_kernal));

  // Kernal for differentiation along the negative diagonal
	Mat dia_kernal = (Mat_<double>(3,3) << 2, 1, 0, 1, 0, -1, 0, -1, -2);
	result.push_back(applyFilter(gray, dia_kernal));

  // Kernal for differentation along the positive diagonal
	Mat dia2_kernal = (Mat_<double>(3,3) << 0, 1, 2, -1, 0, 1, -2, -1, 0);
	result.push_back(applyFilter(gray, dia2_kernal));

	return result;
}