[python] 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?

This question is related to python opencv image-processing

The answer is


add cv2.waitKey(0) in the end.


error: (-215) size.width>0 && size.height>0 in function imshow

This error is produced because the image is not found. So it's not an error of imshow function.


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.


Doesn't need any additional methods after waitKey(0) (reply for above code)

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

Window appears -> Click on the Window & Click on Enter. Window will close.


I also had a -215 error. I thought imshow was the issue, but when I changed imread to read in a non-existent file I got no error there. So I put the image file in the working folder and added cv2.waitKey(0) and it worked.


This is how I solved it:

import cv2
from matplotlib import pyplot
    
img = cv2.imread('path')
pyplot.imshow(img)
pyplot.show()

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)

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()

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.


If you have not made this working, you better put

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

into one file and run it.


If you choose to use "cv2.waitKey(0)", be sure that you have written "cv2.waitKey(0)" instead of "cv2.waitkey(0)", because that lowercase "k" might freeze your program too.


I had the same 215 error, which I was able to overcome by giving the full path to the image, as in, C:\Folder1\Folder2\filename.ext


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)

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.)


You've got all the necessary pieces somewhere in this thread:

if cv2.waitKey(): cv2.destroyAllWindows()

works fine for me in IDLE.


For me waitKey() with number greater than 0 worked

    cv2.waitKey(1)

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