How can I use imshow to display multiple images in multiple windows?

Question

I would like to do something like the following in order to display two images on the screen:

imshow("1", img1);
imshow(\'2\', \'img2\');


        

Answer 1

And here is how to do it in Python:

    cv2.namedWindow("Channels")
    cv2.imshow("Channels", image_channels)

    cv2.namedWindow("Main")
    cv2.imshow("Main", image_main)

You simply create a named window and pass its name as string to imshow.

Answer 2

I have this working in Python, with a caveat:

cv2.imshow("image 1", my_image_1)
cv2.imshow("image 2", my_image_2)
cv2.waitKey(0)

The caveat is that both windows are in the exact same spot on the screen, so it only looks like one window opened up (Ubuntu 14.4). I can mouse drag one to the side of the other.

I'm now looking for how to place the two side by side automagically, which is how I found this question..

Answer 3

If your images are in numpy arrays, you could use numpy.hstack function which merges two arrays into a single and use the cv2.imshow() to display the array.

https://docs.scipy.org/doc/numpy-1.13.0/reference/generated/numpy.hstack.html

Answer 4

Yes, it is possible. The function void imshow(const string& winname, InputArray mat) displays an image in the specified window, where -

• winname – Name of the window.
• image – Image to be shown.

The window is identified by its name. So to display two images(img1, img2), in two different window; use imshow with different name like :-

imshow("1",img1);
imshow("2",img2);

Answer 5

I ran into the problem of having to create an arbitrary number of openCV windows. I had them stored in a list and couldn't simply loop over it to display them:

# images is a list of openCV image object

for img in images:
    cv2.imshow('image',i)

This doesn't work for the trivial reason of images requiring a different label, hence this loop would only display the last item in the list.

That can be solved by using an iterator and python string formatters:

for i, img in enumerator(images):
    cv2.imshow("Image number {}".format(i), img)

Therefore now all images will be displayed since they have been assigned a different label.