display multiple OpenCV imshow() windows separately

Question

I have a VS console application that is built using opencv library. I am displaying image using the opencv imshow function. The thing is that all the imshow windows overlap over each other and it is difficult to toggle between them. How can I prevent the overlap and display them separately and toggle between them

Answer 1

The way to go about this programatically, is to call resizeWindow() to define each windows' size and moveWindow() to place them at specific locations in your screen.

void cv::resizeWindow(const string& winname, int width, int height)
void cv::moveWindow(const string& winname, int x, int y)

Answer 2

Although this is a late reply, you may find it useful to call moveWindow() after each imshow() call. A language independent solution is given here.

Example steps :-

1. call imshow("first image", img1)

2. call moveWindow("first image", img1, 0, 0) // Default position of window is at col,row == 0,0. So, this line is optional.

3. call imshow("second image", img2)
4. set firstImageWidth = width of img1
5. set mySpacing = 40 //vary this to increase/decrease the gap between the image windows.
6. call moveWindow("first image", img1, firstImageWidth + mySpacing , 0)

Then, add these lines to prevent output windows from being forever active.

1. set myTime = 7000 //in milliseconds. Here, 7000 ms == 7 secs to show our image windows.
2. call waitKey(myTime)
3. call waitKey(1) //this is a trick. Otherwise, the windows are opened indefinitely.

At the moment, I am using Java SE8 with OpenCV 4.2. The above method works for me. Screenshot of the above example in action. Here is a Java+OpenCV code snippet for the display part:

...
//display image. Using OpenCV HighGui class methods.
String inputWindowName = "This window shows input image";
String outputWindowName = "This window shows output image";

HighGui displayWindow = new HighGui();

displayWindow.imshow(inputWindowName, img1);

displayWindow.imshow(outputWindowName, img2);
displayWindow.moveWindow(outputWindowName, img1.cols()+40, 0);

displayWindow.waitKey(7000);
displayWindow.waitKey(1);