import numpy as np

import cv2

from PIL import ImageGrab

import time

last_time = time.time()

while(True):

screen = np.array(ImageGrab.grab(bbox=(0,40,600,500)))

print('loop took {} seconds'.format(time.time()-last_time))

last_time = time.time()

cv2.imshow('window' ,cv2.cvtColor(screen, cv2.COLOR_BGR2RGB))

if cv2.waitKey(25)& 0xFF == ord('q'):

cv2.destroyAllWindows()

break