for below code I'm getting this error: OpenCV(3.4.1) C:\build\master_winpack-bindings-win64-vc14-static\opencv\modules\imgproc\src\color.cpp:11147: error: (-215) scn == 3 || scn == 4 in function cv::cvtColor

edit

import cv2

import numpy as np

img = cv2.imread('yuz1.jpg')

frontal = cv2.CascadeClassifier('haarcascade_frontalface_default.xml')

gray = cv2.cvtColor(img, cv2.COLOR_BAYER_BG2BGR)

f_face = frontal.detectMultiScale((gray, 1.1, 4))

for (x, y, w, h) in f_face: cv2.rectangle(img(x, y), (x + y + w + h), (0, 255, 0), 3)

cv2.imshow('Frontal Face', img) cv2.waitKey(0) img.release() cv2.destroyAllWindows()

@berak help me bro please.

python users NEVER do any nessecary checks, so they get those errors.

your videocapture did not open, or it could not retrieve a frame.

cam=cv2.VideoCapture(1); # try 0 here instead
if not cap.isOpened():
    print("no capture!")
    return

while(True): 
    retval,img=cam.read();
    if retval == False:
        print("no image!")
        return

again, you HAVE TO check the outcome of reading resources, opening streams, etc. (same for cv2.imread() or similar)

if you have only a single webcam attached to your box, the only valid camera id would be 0, not 1.