harris corner points coordinates - c++

Question

I am new in opencv so could you help me to find coordinates of points that detected by harris using following code?
source image is img
i want to store coordinates of corner points in matrix S
Mat S;
dst = Mat::zeros( img.size(), CV_32FC1 );
cornerHarris( img, dst, 7, 5, 0.0001, BORDER_DEFAULT );
dst = Mat::zeros( img.size(), CV_32FC1 );
cornerHarris( img, dst, 7, 5, 0.0001, BORDER_DEFAULT );
// Normalizing
normalize( dst, dst_norm, 0, 255, NORM_MINMAX, CV_32FC1, Mat() );
convertScaleAbs( dst_norm, dst_norm_scaled );
for( int j = 0; j < dst_norm.rows ; j++ ) {
for( int i = 0; i < dst_norm.cols; i++ ) {
if( (int) dst_norm.at<float>(j,i) > thresh ) {
S.at<int >(j,i)= (int) dst_norm.at<int>(j,i);
}
}
}

Answer 1

You can store the points coordinates in a Nx2 matrix, where the first column is the x coordinate, and second column is the y coordinate.
You can declare S as an empty CV_32SC1 matrix like:
Mat S(0, 2, CV_32SC1);
(or you can even leave Mat S;, since the type is determined by the first push_back).
Then you can append the coordinates. Inside the if statement, add:
// Create a matrix for the point
Mat pt(1,2,CV_32SC1);
pt.at<int>(0, 0) = i;
pt.at<int>(0, 1) = j;
// Add the point to S
S.push_back(pt);
Note that it can be more straightforward to use std::vector<Point> to store points. In this case, you can declare Svec as:
std::vector<cv::Point> Svec;
and in your if statement you'll have:
Svec.push_back(Point(i,j));
or
Svec.emplace_back(i,j);
If needed, you can convert the vector<Point> to a Mat like:
Mat Z(Svec); // Creates a 2 channels matrix, Nx1
Z = Z.reshape(1); // Creates a 1 channel matrix, Nx2

Answer 2

Mat pt(1,2,CV_32SC1);
pt.at<int>(0, 0) = i;
pt.at<int>(0, 1) = j;
i , j in ur code will be values of i,j counters.
I need to put coordinates of harris corner points