Why resizing the window to the same dimmension actually resizes it?

Question

I have a similar problem as this When I use cv2.imshow the image is bigger than my screen.

What to do? I tried several of the answers without success until I tried the answer dealing with cv2.resizeWindow

However I got some surprising result. Even when I use the above function to resize it to the same height and width of the original (so no resize) the window is resized and I can see the entire image

Why is this happening?

Edit: just in case, I used cv2.namedWindow("Original",cv2.WINDOW_NORMAL)

did you compile opencv with qt support ? – Yunus Temurlenk Jul 19 '22 at 13:27 — Yunus Temurlenk, Jul 19 '22 at 13:27
windows can't be larger than the screen. – Christoph Rackwitz Jul 19 '22 at 17:43 — Christoph Rackwitz, Jul 19 '22 at 17:43

score 0 · Answer 1 · answered Jul 20 '22 at 01:39

The reason you can see the entire image now is because of the cv2.WINDOW_NORMAL flag you passed into the cv2.namedWindow() function.

This displays the image, cropped if it is too big to fit into the screen:

import cv2

img = cv2.imread("image.png")
cv2.imshow("Image", img)
cv2.waitKey(0)

This displays the image, scaled down to a convenient size (and the window can be resized):

import cv2

img = cv2.imread("image.png")

cv2.namedWindow("Image", cv2.WINDOW_NORMAL)
cv2.imshow("Image", img)
cv2.waitKey(0)

This displays the image, scaled down to the specified size... if the specified size can be fit into your screen; else, it will scale the image to be the size of your screen (and the window can be resized):

import cv2

img = cv2.imread("image.png")
h, w, _ = img.shape
cv2.namedWindow("Image", cv2.WINDOW_NORMAL)
cv2.imshow("Image", img)
cv2.resizeWindow("Image", w, h)

cv2.waitKey(0)

So basically,

it is impossible for the window to be bigger than your screen, but the cv2.WINDOW_NORMAL flag made it so that instead of having the image cropped to fit the screen, it got scaled to fit the screen.

Why resizing the window to the same dimmension actually resizes it?

1 Answers1

So basically,