open cv error: (-215) scn == 3 || scn == 4 in function cvtColor: Google Colab

Question

When i try the below code in colab i didn't get any error and also didn't get any output. Also I tried the javascript to access the webcam.

import numpy as np
import cv2

cap = cv2.VideoCapture(0)

while(True):
    # Capture frame-by-frame
    ret, frame = cap.read()

    # Our operations on the frame come here
    gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
    # Display the resulting frame
    cv2.imshow('frame',gray)
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break

    # When everything done, release the capture
    cap.release()
    cv2.destroyAllWindows()

Answer 1

As stated in here most probably the ret value returns false. As a result, the program can't get frames.

• Option #1: Make sure you run the code with administrator privileges, since the program may not access to the camera.

• Option #2: You could use if ret==True: statement, before converting the frame to the grayscale.

  For instance:

  while(True):
      ret, frame = cap.read()
      if ret:
          gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
          # Rest of the code ..