OpenCV in Ubuntu does not show window

Question

I installed a fresh Ubuntu. Downloaded Eclipse via the Shop, installed the CDT plugin via the Plugin Manager in Eclipse (Kepler). I used the Shop to download the OpenCV dev package. After adding the paths in eclipse I wrote a short program.

#include <iostream>
#include "opencv2/opencv.hpp"

int main(int argc, const char * argv[])
{
    cvNamedWindow( "result", CV_WINDOW_AUTOSIZE );

    CvCapture* capture = cvCaptureFromCAM(-1);

    IplImage *newImg;

    while(true)
    {
        newImg = cvQueryFrame( capture );
        if( newImg==0 )
            break;
        cvShowImage( "result", newImg );
    }
    return 0;
}

The program compiles and the debugger shows some values in newImg. But there is no window coming up and shows the result. The camera LED lights, a step through the loop seem to work perfect. Only the output window is missing. The same program runs perfect in XCode on OS X.

Answer 1

Just add small wait between execution of subsequent loops. Use cv::waitKey for this purpose.

#include <iostream>
#include "opencv2/opencv.hpp"

int main(int argc, const char * argv[])
{
    cvNamedWindow( "result", CV_WINDOW_AUTOSIZE );

    CvCapture* capture = cvCaptureFromCAM(-1);

    IplImage *newImg;

    while(true)
    {
        newImg = cvQueryFrame( capture );
        if( newImg==0 )
            break;
        cvShowImage( "result", newImg );
        cv::waitKey(100); //Wait of 100 ms
    }
    return 0;
}