Unhandled exception at Canny edge detector - c++

Question

I want to try Canny edge detector, but when I try to start I receive an Unhandled exception:
Unhandled exception at 0x00007FF97F6C8B9C in canny_project.exe: Microsoft C++ exception: cv::Exception at memory location 0x0000002485D89860
Below is the code that I implemented In VS2012.
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include <iostream>
#include <stdio.h>
#include <stdlib.h>
using namespace std;
using namespace cv;
int main(int, char**)
{
namedWindow("Edges", CV_WINDOW_NORMAL);
CvCapture* capture = cvCaptureFromCAM(-1);
cv::Mat frame; cv::Mat out; cv::Mat out2;
while (1) {
frame = cvQueryFrame(capture);
GaussianBlur(frame, out, Size(5, 5), 0, 0);
cvtColor(out, out2, CV_BGR2GRAY); // produces out2, a one-channel image (CV_8UC1)
Canny(out2, out2, 100, 200, 3); // the result goes to out2 again,but since it is still one channel it is fine
if (!frame.data) break;
imshow("Edges", out2);
char c = cvWaitKey(33);
if (c == 'c') break;
}
return 0;
}
Thanks in advance

Answer 1

The problem is probably you are using cvCaptureFromCAM wrong.
cvCaptureFromCAM(0) // not -1
Why do you use OpenCV with C-Code? Use VideoCapture instead CvCapture.

Answer 2

Please try this instead and tell me whether images are shown or not and try different device numbers too:
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include <iostream>
#include <stdio.h>
#include <stdlib.h>
using namespace std;
using namespace cv;
int main(int, char**)
{
cv::namedWindow("Capture");
int deviceNum = 0; // please try different device numbers too like -1, 1, 2, ...
cv:VideoCapture capture(deviceNum);
cv::Mat frame;
if(!capture.isOpened())
{
std::cout << "Could not open device " << deviceNum << std::endl;
return 0;
}
while (true)
{
capture >> frame; // = cvQueryFrame(capture);
//if (!frame.data) break;
if(frame.empty())
{
std::cout << "could not capture a legal frame" << std::endl;
continue;
//break;
}
cv::imshow("Capture", frame);
char c = cv::waitKey(33);
if (c == 'c') break;
}
std::cout << "press any key to exit" << std::endl;
cv::waitKey(0); // wait until key pressed
return 0;
}

Answer 3

cvCaptureFromCAM(-1) has wrong argument, use 0, if you have just one camera connected. In addition, in C API, when you finished working with video, release CvCapture structure with cvReleaseCapture(), or use Ptr<CvCapture> that calls cvReleaseCapture() automatically in the destructor. Have a try, please, this example, to see if you access your camera properly.