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Hi, I am trying to implement Harris corner detection in OpenCV C++ without using the built-in function CornerHarris.

This is the code I wrote and is not working. What is the mistake in the code?

int main(int argc, const char** argv) {

Mat src;

Mat grad_x, grad_y;
Mat Ixx,Ixy,Iyy;
Mat H;
Mat Hxx, Hxy, Hyy;
Mat tr, det, Response;

double sigmaX, sigmaY;
Size gaussian_window_size = Size(3, 3);

cv::CommandLineParser parser(argc, argv,
    "{@input   |D:/Codebases/VS_Workspace/DIP_Book_Images/chessboard.png|input image}"
);


const String window_name = "Harris Corner Demo ";
int ksize = 3;
int scale = 1;
int delta = 0;
int ddepth = CV_16S;


String imageName = parser.get<String>("@input");
src = imread(samples::findFile(imageName), IMREAD_GRAYSCALE); 
src.convertTo(src, CV_32F);


if (src.empty())
{
    cout << "Error reading image " << imageName << endl;
    return EXIT_FAILURE;
}


Sobel(src, grad_x, ddepth, 1, 0, ksize, scale, delta, BORDER_DEFAULT);



Sobel(src, grad_y, ddepth, 0, 1, ksize, scale, delta, BORDER_DEFAULT);


Ixx = grad_x.mul(grad_x);
Ixy = grad_x.mul(grad_y);
Iyy = grad_y.mul(grad_y);



sigmaX = 0;
sigmaY = 0;
GaussianBlur(Ixx, Hxx, gaussian_window_size,  sigmaX, sigmaY, BORDER_DEFAULT);
GaussianBlur(Ixy, Hxy, gaussian_window_size,  sigmaX, sigmaY, BORDER_DEFAULT);
GaussianBlur(Iyy, Hyy, gaussian_window_size,  sigmaX, sigmaY, BORDER_DEFAULT);

tr = Hxx + Hyy; 
det = Hxx.mul(Hyy) - Hxy.mul(Hxy);
Mat tr2 = tr.mul(tr);
Mat tr3 = tr2*0.04f;  
Response = det - tr3;

Mat max_resp; 
dilate(Response, max_resp, getStructuringElement(MORPH_RECT, Size(3, 3), Point(-1, -1)));


Mat t1, t2;
t1 = (Response == max_resp);
t2 = Response > 1e4;

Mat corners = t1&t2;


imshow(window_name, corners);

char key = (char)waitKey(0);


return 0;

}

• Thank you.

Hi, I am trying to implement Harris corner detection in OpenCV C++ without using the built-in function CornerHarris.

This is the code I wrote and is not working. What is the mistake in the code?

int main(int argc, const char** argv)
{
 
{
Mat src;
 Mat grad_x, grad_y;
 Mat Ixx,Ixy,Iyy;
 Mat H;
 Mat Hxx, Hxy, Hyy;
 Mat tr, det, Response;
 double sigmaX, sigmaY;
 Size gaussian_window_size = Size(3, 3);
 cv::CommandLineParser parser(argc, argv,
 "{@input |D:/Codebases/VS_Workspace/DIP_Book_Images/chessboard.png|input image}"
 );
 const String window_name = "Harris Corner Demo ";
 int ksize = 3;
 int scale = 1;
 int delta = 0;
 int ddepth = CV_16S;
 String imageName = parser.get<String>("@input");
 src = imread(samples::findFile(imageName), IMREAD_GRAYSCALE);
 src.convertTo(src, CV_32F);
 if (src.empty())
 {
  cout << "Error reading image " << imageName << endl;
 return EXIT_FAILURE;
 }
 Sobel(src, grad_x, ddepth, 1, 0, ksize, scale, delta, BORDER_DEFAULT);
 Sobel(src, grad_y, ddepth, 0, 1, ksize, scale, delta, BORDER_DEFAULT);
 Ixx = grad_x.mul(grad_x);
 Ixy = grad_x.mul(grad_y);
 Iyy = grad_y.mul(grad_y);
 sigmaX = 0;
 sigmaY = 0;
 GaussianBlur(Ixx, Hxx, gaussian_window_size, sigmaX, sigmaY, BORDER_DEFAULT);
 GaussianBlur(Ixy, Hxy, gaussian_window_size, sigmaX, sigmaY, BORDER_DEFAULT);
 GaussianBlur(Iyy, Hyy, gaussian_window_size, sigmaX, sigmaY, BORDER_DEFAULT);
 tr = Hxx + Hyy;
 det = Hxx.mul(Hyy) - Hxy.mul(Hxy);
 Mat tr2 = tr.mul(tr);
 Mat tr3 = tr2*0.04f;
 Response = det - tr3;
 Mat max_resp;
 dilate(Response, max_resp, getStructuringElement(MORPH_RECT, Size(3, 3), Point(-1, -1)));
 Mat t1, t2;
 t1 = (Response == max_resp);
 t2 = Response > 1e4;
 Mat corners = t1&t2;
 imshow(window_name, corners);
 char key = (char)waitKey(0);
 return 0;
}
 
} 
 
Thank you.