cv::matchShapes method implementation giving error - iphone

Question

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.
Here is my code:-
- (void)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);
}
}
for( size_t i = 0; i < contours.size(); i++ )
{
double value= cv::matchShapes(contours[i], contours1[i], CV_CONTOURS_MATCH_I1, 0);
NSLog(#"%f",value);
}
}
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.
Error:-
OpenCV Error: Assertion failed (contour1.checkVector(2) >= 0 && contour2.checkVector(2) >= 0 && (contour1.depth() == CV_32F || contour1.depth() == CV_32S) && contour1.depth() == contour2.depth()) in matchShapes, file /Users/Aziz/Documents/Projects/opencv_sources/trunk/modules/imgproc/src/contours.cpp, line 1705
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!

Answer 1

std::vector<std::vector<cv::Point> > contours1;
You can't apply matchShapes to such type. You can apply it for each (one) contour, not for group (array) of contours. For example:
cv::matchShapes(contours[0], contours1[0], CV_CONTOURS_MATCH_I1, 0);