How to resize window in opencv2 python

Question

I am using opencv 2 with a webcam. I can get the video stream and process it, but I can't seem to figure out a way to resize the display window. I have some video images stacked horizontally, but the image dimension is very small that it's difficult to see things.

My code is pretty simple, and along the lines of this:

cv2.namedWindow("main")

....

result = np.hstack((res2, foreground))
result = np.hstack((ff, result))

cv2.imshow("main", result)
cv2.waitKey(20)

The opencv documentation states:

namedWindow
flags – Flags of the window. Currently the only supported flag is CV_WINDOW_AUTOSIZE . If this is set, the window size is automatically adjusted to fit the displayed image (see imshow() ), and you cannot change the window size manually.

But qt backends apparently have extra flags. I don't have a qt backend. Is there a way for me to increase the size of the images so that I can see them?

Alexey · Accepted Answer · 2013-05-29 14:14:04Z

19

Yes, unfortunately you can't manually resize a nameWindow window without Qt backend. Your options:

use cv2.resize function to resize the image to desired size prior to displaying the image
install OpenCV with Qt backend support and use cv2.namedWindow("main", CV_WINDOW_NORMAL)

edited May 29, 2013 at 14:14

answered May 29, 2013 at 14:08

Alexey

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4 Comments

user391339 Over a year ago

how did you use resize?

uutsav Over a year ago

cv2.resize(image, (0, 0), fx=0.5, fy=0.5) will resize both axes by half while cv2.resize(image, (100, 50)) will resize to have width 100 and height 50 pixels.

Anoop Toffy Over a year ago

How to add an image to the window?

Monty _s Flying Circus Over a year ago

How can we check whether we have Qt backend?

Chris · Accepted Answer · 2021-02-04 12:11:22Z

18

Simply write

cv2.namedWindow("main", cv2.WINDOW_NORMAL)

and then manually resize it to your desired size

cv2.resizeWindow('image', 900, 900)

edited Feb 4, 2021 at 12:11

Chris

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answered Jun 28, 2016 at 16:08

Shahrukh khan

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1 Comment

San Askaruly Over a year ago

and in the next line: cv2.resizeWindow('image', 900, 900)

Dave Cousineau · Accepted Answer · 2014-07-21 02:12:47Z

5

You can use the WINDOW_NORMAL flag when calling the namedWindow function as shown below. This will allow you to resize your window.

namedWindow("Image", WINDOW_NORMAL);

Check the namedWindow function documented here

edited Jul 21, 2014 at 2:12

Dave Cousineau

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answered Jul 21, 2014 at 2:07

rajkn90

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1 Comment

bobt Over a year ago

Doesn't work for me on Windows 11

user1245262 · Accepted Answer · 2021-08-27 21:18:14Z

1

What worked for me was to resize the image instead of the window (I never did manage to get window resizing to work):

import cv2

img = cv2.imread('your_image.jpg')
res = cv2.resize(img, dsize=(500,500), interpolation=cv2.INTER_CUBIC)
cv2.namedWindow("Resized", cv2.WINDOW_NORMAL)
cv2.imshow("Resized", res)

answered Aug 27, 2021 at 21:18

user1245262

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Comments

Ajani Timothy · Accepted Answer · 2022-03-11 04:39:36Z

0

It has to with the resolution of pc camera run this code to confirm

cap = cv2.VideoCapture(0)
width = cap.get(cv2.CAP_PROP_FRAME_WIDTH)
height = cap.get(cv2.CAP_PROP_FRAME_HEIGHT)
print(width, height)

most likely its 640 x 480 px. You might have to reduce the size of the image to fit the screen

answered Mar 11, 2022 at 4:39

Ajani Timothy

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Comments

RoadieRich · Accepted Answer · 2016-03-28 14:02:08Z

-3

As per the docs, you need to create your window with autosize true.

cv2.namedWindow("main", cv2.WINDOW_AUTOSIZE)

Your call to imshow will then automatically resize the window to fit your image.

edited Mar 28, 2016 at 14:02

RoadieRich

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answered May 29, 2013 at 14:05

Blutack

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1 Comment

Salvador Medina Over a year ago

The option WINDOW_AUTOSIZE is as default and sets the size of the window to the actual fixed size of the image.

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