The cv2.imshow command does not work properly in opencv-python

Question

I am using opencv 2.4.2, python 2.7 The following simple code created a window with the correct name, but its contents are simply empty and do not display the image:

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

Does anyone know about this issue?

Answer 1

imshow() only works with waitKey() :

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

(The entire message loop needed to update the window is hidden there.)

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

Read more: HighGUI is a simplified interface for displaying images and videos from OpenCV code. It should be so simple:

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

Answer 3

You should 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) 

Answer 4

I ran into the same problem. I tried to read the image from IDLE and tried to display it using cv2.imshow() , but the viewport freezes and shows that pythonw.exe not responding when trying to close the window.

The message below provides a possible explanation of why this is happening.

pythonw.exe is not responding

"In principle, do not do this from IDLE. Write a script and run it from a shell or script directly if on Windows, calling it the extension .pyw and double-clicking on it. There seems to be a conflict between the IDLE's own event loop and graphical tools GUI interfaces.

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

Answer 5

If you are working inside the Python console, follow these steps:

 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 continue to execute other commands.

Answer 6

add cv2.waitKey(0) at the end.

Answer 7

I had a similar problem and it was solved by uninstall

 import gtk, pygtk # remove these 

I use Linux, so it may be that gtk will not work. I was going to use it to get the screen size, to put the two images shown next to each other, but I guess I need to do a different way to do this. Hardcoded is 1920x1080 at the moment ..

Answer 8

You have all the necessary fragments in this thread:

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

works great for me in IDLE.

Answer 9

If you decide to use "cv2.waitKey (0)", make sure you write "cv2.waitKey (0)" instead of "cv2.waitkey (0)" because this lowercase "k" may freeze your program too.

Answer 10

If you haven’t done this, 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.

Answer 11

I have waitKey () with a number greater than 0

  cv2.waitKey(1) 

Answer 12

I used openCV with pyplot and was able to get the image to render in the current jupyter window using pyplots imshow and show.

  import matplotlib.pyplot as plt import matplotlib.image as mpimg # First, we need to read in an image image = mpimg.imread('my_image.jpg') plt.imshow(image) # then using openCV algorithms on the image, eg grey scale import cv2 gray = cv2.cvtColor(image, cv2.COLOR_RGB2GRAY) #grayscale conversion # finally output the result through pyplot in the current window plt.imshow(gray, cmap='gray') plt.show() 

Answer 13

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

This error is caused because the image was not found. So this is not an imshow function error.