cv2.imshow command doesn't work properly in opencv-python

Question

imshow() only works with waitKey():

import cv2
img = cv2.imread('C:/Python27/03323_HD.jpg')
cv2.imshow('ImageWindow', img)
cv2.waitKey()

(The whole message-loop necessary for updating the window is hidden in there.)

I found the answer that worked for me here: http://txt.arboreus.com/2012/07/11/highgui-opencv-window-from-ipython.html

If you run an interactive ipython session, and want to use highgui windows, do cv2.startWindowThread() first.

In detail: HighGUI is a simplified interface to display images and video from OpenCV code. It should be as easy as:

import cv2
img = cv2.imread("image.jpg")
cv2.startWindowThread()
cv2.namedWindow("preview")
cv2.imshow("preview", img)

You must use cv2.waitKey(0) after cv2.imshow("window",img). Only then will it work.

import cv2
img=cv2.imread('C:/Python27/03323_HD.jpg')
cv2.imshow('Window',img)
cv2.waitKey(0)

If you are running inside a Python console, do this:

img = cv2.imread("yourimage.jpg")

cv2.imshow("img", img); cv2.waitKey(0); cv2.destroyAllWindows()

Then if you press Enter on the image, it will successfully close the image and you can proceed running other commands.

I faced the same issue. I tried to read an image from IDLE and tried to display it using cv2.imshow(), but the display window freezes and shows pythonw.exe is not responding when trying to close the window.

The post below gives a possible explanation for why this is happening

pythonw.exe is not responding

"Basically, don't do this from IDLE. Write a script and run it from the shell or the script directly if in windows, by naming it with a .pyw extension and double clicking it. There is apparently a conflict between IDLE's own event loop and the ones from GUI toolkits."

When I used imshow() in a script and execute it rather than running it directly over IDLE, it worked.

add cv2.waitKey(0) in the end.

Method 1:

The following code worked for me. Just adding the destroyAllWindows() didn't close the window. Adding another cv2.waitKey(1) at the end did the job.

im = cv2.imread("./input.jpg")
cv2.imshow("image", im)
cv2.waitKey(0)
cv2.destroyAllWindows()
cv2.waitKey(1)

credit : https://stackoverflow.com/a/50091712/8109630

Note for beginners:

• This will open the image in a separate window, instead of displaying inline on the notebook. That is why we have to use the destroyAllWindows() to close it later.
• So if you don't see a separate window pop up, check if it is behind your current window.
• After you view the image press a key to close the popped up window.

Method 2:

If you want to display on the Jupyter notebook.

from matplotlib import pyplot as plt
import cv2

im = cv2.imread("./input.jpg")
color = cv2.cvtColor(im, cv2.COLOR_BGR2RGB)
plt.imshow(color)
plt.title('Image')
plt.show()