circle hough center co-ordinates - c++

Question

In opencv, I am using Hough transform for circle finder here is the code
HoughCircles (diff, circles, CV_HOUGH_GRADIENT, 2, src.cols / 5, 200, 80, 20, 62);
for (size_t i = 0; i < circles.size(); i++ )
{
//if(circles[i][2]<62)
{
Point center(cvRound(circles[i][0]), cvRound(circles[i][1]));
int radius = cvRound(circles[i][2]);
// draw the green circle center
circle( src, center, 3, Scalar(0,255,255), -1, 8, 0 );
// draw the blue circle outline
circle(src, center, radius, Scalar(0,255,0), 3, 8, 0 );
}
}
The problem I am facing is that sometimes in case it found 3 circles, the third one center coordinates are fraction not integer as supposed to be also in case it found 4 circles it give this error
Unhandled exception at 0x75ebc41f in xyz.exe: Microsoft C++ exception:
cv::Exception at memory location 0x002df08c..
if I tried to cout the center co-ordinates.

Answer 1

Hmm this is interesting. I ran your code and filled-in the before and after and didn't have any problems. To be honest, I've only tested on a linux and mac machine. Here is my full length code, try that and see what happens. Also, check this solution here.
int main(int argc, char* argv[]) {
VideoCapture capture(0);
if (!capture.isOpened()) {
LOG(FATAL) << "COULD NOT OPEN CAPTURE";
}
Mat frame;
capture >> frame;
if (frame.empty()) {
LOG(FATAL) << "FRAME IS EMPTY!";
}
char key;
while ((int)key != 27) {
capture >> frame;
Mat gray;
cvtColor(frame, gray, CV_BGR2GRAY);
GaussianBlur(gray, gray, Size(9, 9), 2, 2);
vector<Vec3f> circles;
HoughCircles(gray, circles, CV_HOUGH_GRADIENT, 2, gray.cols/5,200,80,20,62);
for (size_t i = 0; i < circles.size(); ++i) {
Point center(cvRound(circles[i][0]), cvRound(circles[i][1]));
int radius = cvRound(circles[i][2]);
// draw the green circle center
circle(frame, center, 3, Scalar(0,255,255), -1, 8, 0 );
// draw the blue circle outline
circle(frame, center, radius, Scalar(0,255,0), 3, 8, 0 );
}
imshow("frame", frame);
key = waitKey(1);
}
return 0;
}