OpenCV imshow() in a loop to show image

Question

I'd like to create a C++ program with OpenCV which would allow me to continuously run a loop to ask a user what to do with an image. For example the user can enter a specific number to execute a command. The code I have as an example is:

int main()
{
    int choose = -1;


    for (;;)
    {

    cin >> choose;

    if (choose == 0)
    {

        Mat img = imread(fileName1);//, CV_LOAD_IMAGE_GRAYSCALE); 

        if (!img.data)
        {
            cout << "Unable to load file." << endl;
        }
        else
        {
            namedWindow(fileName1, 1);
            imshow(fileName1, img);
        }
    }
    else if (choose == 1)
    {
        Mat img = imread(fileName2, CV_LOAD_IMAGE_GRAYSCALE);

        if (!img.data)
        {
            cout << "Unable to load file." << endl;
        }
        else
        {
            namedWindow(fileName2, 1);
            imshow(fileName2, img);
        }
    }
}


waitKey(0);

return 0;

}

The window where the image is supposed to load is just filled with grey. I don't have any problems loading the image when it is not in a loop. Can anyone help me figure out why this causes a problem please?

EDIT: Of course, forgot the waitKey(0) although even if I did have that, when I go back to the start of the loop to enter a number the window that was opened crashes for some reason.

Answer 1

Use waitKey to get the pressed key instead of cin. Alternatively as said in the comments do a waitKey(1) after imshow.