Revision history [back]

How to use cv::matchShapes method from coding point of view in c or c++

Hi all, My objective is to find the pattern in the image captured from camera for this I found the cv::matchShapes method of opencv to implement it.

When I have implemented this method it is making the app crash on matchShapes method.Might be I have done something wrong:-

I exactly do not know how to use this method in order to find the match shape in my query image.This is what I tried.

Please help me in providing some code that can run properly.

Here is my code:-

- (std::vector<std::vector<cv::Point> >)tryingMatchShapes:(cv::Mat)_image _image1:(cv::Mat)_image1
{
    std::vector<std::vector<cv::Point> > squares;

    cv::Mat pyr, timg, gray0(_image.size(), CV_8U), gray;
    int thresh = 50, N = 11;
    cv::pyrDown(_image, pyr, cv::Size(_image.cols/2, _image.rows/2));
    cv::pyrUp(pyr, timg, _image.size());
    std::vector<std::vector<cv::Point> > contours;
    for( int c = 0; c < 3; c++ ) {
        int ch[] = {c, 0};
        mixChannels(&timg, 1, &gray0, 1, ch, 1);
        for( int l = 0; l < N; l++ ) {
            if( l == 0 ) {
                cv::Canny(gray0, gray, 0, thresh, 5);
                cv::dilate(gray, gray, cv::Mat(), cv::Point(-1,-1));
            }
            else {
                gray = gray0 >= (l+1)*255/N;
            }
            cv::findContours(gray, contours, CV_RETR_LIST, CV_CHAIN_APPROX_SIMPLE);

        }
    }
            cv::Mat pyr1, timg1, gray2(_image1.size(), CV_8U), gray1;
            cv::pyrDown(_image1, pyr1, cv::Size(_image1.cols/2, _image1.rows/2));
            cv::pyrUp(pyr1, timg1, _image1.size());
            std::vector<std::vector<cv::Point> > contours1;
            for( int c = 0; c < 3; c++ ) {
                int ch[] = {c, 0};
                mixChannels(&timg1, 1, &gray2, 1, ch, 1);
                for( int l = 0; l < N; l++ ) {
                    if( l == 0 ) {
                        cv::Canny(gray2, gray1, 0, thresh, 5);
                        cv::dilate(gray1, gray1, cv::Mat(), cv::Point(-1,-1));
                    }
                    else {
                        gray1 = gray2 >= (l+1)*255/N;
                    }
                    cv::findContours(gray1, contours1, CV_RETR_LIST, CV_CHAIN_APPROX_SIMPLE);



                }
            }
    cv::matchShapes(contours, contours1, CV_CONTOURS_MATCH_I1, 0);
 return squares;
}


UIImage *testImage = [UIImage imageNamed:@"note_with_marks (1).png"];    
[self.imageView setImage:testImage];
cv::Mat forground = [testImage CVMat]; 
UIImage *testImage2 = [UIImage imageNamed:@"1.png"];    
cv::Mat forground2 = [testImage2 CVMat];
[self tryingMatchShapes:forground _image1:forground2];
The app is getting crashed on this line:-

    cv::matchShapes(contours, contours1, CV_CONTOURS_MATCH_I1, 0);

Error:-

OpenCV Error: Assertion failed (0 <= i && i < (int)vv.size()) in getMat, file /Users/Aziz/Documents/Projects/opencv_sources/trunk/modules/core/src/matrix.cpp, line 922

I am sure I am doing something wrong in the code but exactly what that I am not able to figure out.

Please some body help me in implementing this method from coding point of view. Please I need some coding help.I have already gone through I lot of theoretical concepts.

Thanks in advance!