OpenCV-Python does not work with matplotlib.pyplot

[lewjiayi]

System information (version)

• OpenCV => 4.4.0.44
• Operating System / Platform => Ubuntu 18.04.5
• Compiler => Visual Studio Code

Detailed description

When I import matplotlib.pyplot and uses cv2.imshow the window will just close on any key I press except for spacebar and Esc. The following code will not run but it returns no error, it simply stop running. It started after I upgrade my opencv from 4.2 to 4.4. I had tried to import matplotlib only and other matplotlib modules and they does not cause any problem.

Matplotlib version 3.3.2

Steps to reproduce

import cv2
import matplotlib.pyplot

cap = cv2.VideoCapture("video/7.mp4")
while True:
	(ret, frame) = cap.read()
        if not ret:
                break
	cv2.imshow("Processed Output", frame)
	if cv2.waitKey(1) & 0xFF == ord('q'):
		break
cv2.destroyAllWindows()
cap.release()
print("End")

When the video ends byitself, End will be printed. When I press any key excpet spacebar and Esc while video playing, End will not be printed. I had tried with other code replacing print("End") and they will not work as well. So I pretty sure it crashes.

Issue submission checklist

• I report the issue, it's not a question
• I checked the problem with documentation, FAQ, open issues,
  answers.opencv.org, Stack Overflow, etc and have not found solution
• I updated to latest OpenCV version and the issue is still there
• There is reproducer code and related data files: videos, images, onnx, etc

[skvark]

Probably a duplicate of this: #386

Try matplotlib.use('tkagg'). If that solves the issue, then the problem is the same as in the linked issue (PyQt5 and OpenCV Qt5 have issues when used together).

[lewjiayi]

Probably a duplicate of this: #386

Try matplotlib.use('tkagg'). If that solves the issue, then the problem is the same as in the linked issue (PyQt5 and OpenCV Qt5 have issues when used together).

It works! Thank you!

For future reference, your code must follow the sequnce as below in order to solve the issue.

import matplotlib
matplotlib.use('tkagg')
import matplotlib.pyplot as plt