OpenCV Gives an error when using the imgproc functions

Question

when I compile and run this code, I get an error. It compiles, but when I try to run it, it gives the following error:

The application has requested the Runtime to terminate in an unusual way.

This is the code:

#include <opencv2/opencv.hpp>
#include <string>

int main() {
    cv::VideoCapture c(0);
    double rate = 10;
    bool stop(false);
    cv::Mat frame;
    cv::namedWindow("Hi!");
    int delay = 1000/rate;
    cv::Mat corners;
    while(!stop){
        if(!c.read(frame))
            break;
        cv::cornerHarris(frame,corners,3,3,0.1);
        cv::imshow("Hi!",corners);
        if(cv::waitKey(delay)>=0)
            stop = true;
    }
    return 0;
}

BTW, I get the same error when using the Canny edge detector.

Answer 1

Your corners matrix is declared as a variable, but there is no memory allocated to it. The same with your frame variable. First you have to create a matrix big enough for the image to fit into it.

I suggest you first take a look at cvCreateImage so you can learn how basic images are created and handled, before you start working with video streams.

Answer 2

Make sure the capture is ready, and the image is ok:

if(!cap.IsOpened())
   break;

if(!c.read(frame))
        break;

if(frame.empty())
    break;

Answer 3

You need to convert the image to grayscale before you use the corner detector:

cv::Mat frameGray;
cv::cvtColor(frame, frameGray, CV_RGB2GRAY);