Dev C++ Crashing with OpenCV

1
votes

I'm writing a simple algorithm to convert a RGB image, from my webcam, to HSV, it's compiling fine, but crashes when the .exe is executed.

#include <cv.h>
#include <highgui.h>

int main(int argc, char** argv)
    {
     // Cria uma janela.
    cvNamedWindow("imagem", CV_WINDOW_AUTOSIZE);
    // Cria a conexão com a webcam.
    CvCapture *capture = cvCreateCameraCapture(0);
    // Variável que armazena o frame.
    IplImage *frame;
    IplImage* imghsv = cvCreateImage(cvGetSize(frame),8,3);
    while(1)
        {
        // Variável  recebe o frame.
        frame = cvQueryFrame(capture);
        if(!frame) break;
        cvCvtColor(frame, imghsv, CV_BGR2HSV);
        // Exibe o frame na janela.
        cvShowImage("imagem", frame);
        cvShowImage("hsv", imghsv);
        // Encerra o loop com uma tecla.
        if( cvWaitKey(100) == 27 ) break;
    }
    // Libera a memória utiliazada.
    cvReleaseImage(&frame);
    cvReleaseImage(&imghsv);
    cvReleaseCapture(&capture);
    // Fecha a janela.
    cvDestroyWindow("imagem");
    cvDestroyWindow("hsv");
}

Without the line "IplImage* imghsv = cvCreateImage(cvGetSize(frame),8,3);" the .exe works, but the algorithm only shows my image.

I'm using Dev C++ 4.9.9.2 and OpenCV 2.1 in Windows XP SP3. Sorry about the english. Thanks

The problem was solved replacing IplImage *frame; by IplImage *frame=cvQueryFrame(capture);.

2
copencvwindows-xpdev-c++
Ya both are same.. The second image doest know the size of frame. Please have a look at my code. – 2vision2

2 Answers

2
votes
IplImage *frame;
IplImage* imghsv = cvCreateImage(cvGetSize(frame),8,3);

Your frame image has not been yet allocated, you shouldn't create your hsv image before actually grabbing a frame.

Also note :

cvReleaseImage(&frame);

You should not release an image grabbed from cvQueryFrame(), OpenCV will take care of it.

From the OpenCV documentation :

The function cvQueryFrame grabs a frame from a camera or video file, decompresses it and returns it. This function is just a combination of GrabFrame and RetrieveFrame , but in one call. The returned image should not be released or modified by the user. In the event of an error, the return value may be NULL.

CvCapture *capture = cvCreateCameraCapture(0);

You should also check the return value of cvCreateCameraCapture, which could be NULL.

IplImage* imghsv = cvCreateImage(cvGetSize(frame),8,3);

You should use IPL_DEPTH_8U instead of 8.

0
votes

This code works perfectly... Some lines missing in your code... Have a look.

#include <cv.h>
#include <highgui.h>

int main(int argc, char** argv)
    {
     // Cria uma janela.
    cvNamedWindow("imagem", CV_WINDOW_AUTOSIZE);
    cvNamedWindow("hsv", CV_WINDOW_AUTOSIZE);  // added in orig code
    // Cria a conexão com a webcam.
    CvCapture *capture = cvCreateCameraCapture(0);
    // Variável que armazena o frame.
    IplImage *frame;
    IplImage* imghsv;
//    IplImage* imghsv = cvCreateImage(cvGetSize(frame),8,3);
    while(1)
        {
        // Variável  recebe o frame.
        frame = cvQueryFrame(capture);
        imghsv = cvCreateImage(cvGetSize(frame),8,3);  /// changed from orig code.
        if(!frame) break;
        cvCvtColor(frame, imghsv, CV_BGR2HSV);
        // Exibe o frame na janela.
        cvShowImage("imagem", frame);
        cvShowImage("hsv", imghsv);
        // Encerra o loop com uma tecla.
        if( cvWaitKey(100) == 27 ) break;
    }
    // Libera a memória utiliazada.
    cvReleaseImage(&frame);
    cvReleaseImage(&imghsv);
    cvReleaseCapture(&capture);
    // Fecha a janela.
    cvDestroyWindow("imagem");
    cvDestroyWindow("hsv");
}