cv2 imshow doesnt open window again after closing and opening again, when used with threads

Question

In the sample code below,

import cv2
from threading import Thread

class Person_Item_Association(object):
    def __init__(self):
        self.stop = False

    def start_camera(self):
        self.stop =False
        camera_thread = Thread(target=self.start_analysis)
        camera_thread.start()

    def stop_camera(self):
        self.stop = True

    def start_analysis(self):
        cap = cv2.VideoCapture(0)

        while not self.stop:
            ret,image = cap.read()
            cv2.imshow("frame",image)
            cv2.waitKey(1)

        cap.release()
        print("resource released")
        cv2.destroyAllWindows()

I do the following sequence, call obj.start_camera(), obj.stop_camera(), cv2.imshow() opens a window , but when i again do obj.start_camera() and obj.stop_camera(), it doesn't open a window. What is wrong here ?

Answer 1

You can use multiprocessing module instead of threading modeule to mitigate the issue. But I am still unable to find how to fix this with threading.

Take a look at a similar question.