Python openCV drawing functions does not work?!

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Actually I had the same problem.All you need to do is:

img = np.zeros((512,512,3), np.uint8)
img1= cv2.line(img,(0,0),(511,511),(255,0,0),5)

Thats it..renaming the variable for line does the trick.Now you can use imshow to display the image. Do visit my blog li8bot for further info on opencv with python

This problem also occurred with me this morning, while i started leaning OpenCV, below solution worked for me, probably this will work for you people also:

import numpy as np
import cv2

img = np.zeros((512, 512, 3), np.uint8)
img= cv2.line(img, (0, 0), (511, 511), (255, 0, 0), 5)

cv2.imshow("Image", img)
cv2.waitKey(0)

Basically, window with line disappears in mili-seconds, so we just need to **add a infinite wait key so that window does not get disappear automatically.