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

Posted on

Question :

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

I’m using opencv 2.4.2, python 2.7
The following simple code created a window of the correct name, but its content is just blank and doesn’t show the image:

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

does anyone knows about this issue?

Asked By: top.eng

||

Answer #1:

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.)

Answered By: berak

Answer #2:

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)
Answered By: Akhorus

Answer #3:

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)
Answered By: AdityaIntwala

Answer #4:

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.

Answered By: Dharma

Answer #5:

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.

Answered By: rkdasari

Answer #6:

add cv2.waitKey(0) in the end.

Answered By: Pygirl

Answer #7:

For me waitKey() with number greater than 0 worked

    cv2.waitKey(1)
Answered By: Rambod

Answer #8:

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()
Answered By: Minzey

Leave a Reply

Your email address will not be published.