How to show an image in opencv when in a loop?

I have IplImage * structures, and I am trying to have a loop to show an Image to a user, and ask them if the shown image is OK.

Basically, when displaying an ima开发者_StackOverflow中文版ge in passing this method of using cvShowImage works. However, since it is looped it doesn't seem to be working. I only see a gray screen until I hit y. If I hit y and it breaks, it then shows me the images.

Here is the gist of what I have.

    char response;
    int showing_img = 1;

    SaveImage1(); // these methods just save the IplImage structure.
    SaveImage2();

    cvShowImage("Image 1", img_1);
    cvShowImage("Image 2", img_2);

    while (1)
    {
        if (!showing_img)
        {
            cvShowImage("Image 1", img_1);
            cvShowImage("Image 2", img_2);
            showing_img = 1;
        }

        printf("Are these good?  y/n please\n");
        scanf("%c", &response);
        if (response == 'y')
        {
            break;
        }
        if (response == 'n')
        {
            cvReleaseImage(&img_1);
            cvReleaseImage(&img_2);
            showing_img = 0;
            SaveImage1(1);
            SaveImage2(1);
        }
    }

How should I be doing this, instead?

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You have to let the system update the images. Insert a call to cvWaitKey in the loop, that should fix your problem.