OpenCV error: Assertion faild in a simple face detection beginers code

I'm starting to learn how to use OpenCV and face detection. I'm following code example from: https://opencv-python-tutroals.readthedocs.io/en/latest/py_tutorials/py_objdetect/py_face_detection/py_face_detection.html#face-detection .

import cv2
face_cascade = cv2.CascadeClassifier('haarcascade_frontalface_default.xml')
eye_cascade = cv2.CascadeClassifier('haarcascade_eye.xml')

img = cv2.imread('face.jpg')
gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)

faces = face_cascade.detectMultiScale(gray, 1.3, 5)
for (x,y,w,h) in faces:
    img = cv2.rectangle(img,(x,y),(x+w,y+h),(255,0,0),2)
    roi_gray = gray[y:y+h, x:x+w]
    roi_color = img[y:y+h, x:x+w]
    eyes = eye_cascade.detectMultiScale(roi_gray)
    for (ex,ey,ew,eh) in eyes:
        cv2.rectangle(roi_color,(ex,ey),(ex+ew,ey+eh),(0,255,0),2)

cv2.imshow('img',img)
cv2.waitKey(0)
cv2.destroyAllWindows()

I keep getting this:

Traceback (most recent call last):
  File "D:/Korisnici/Josipa/Desktop/CV/face_detection.py", line 10, in <module>
    faces = face_cascade.detectMultiScale(gray, 1.3, 5)
error: OpenCV(4.1.1) C:\projects\opencv-python\opencv\modules\objdetect\src\cascadedetect.cpp:1689: error: (-215:Assertion failed) !empty() in function 'cv::CascadeClassifier::detectMultiScale'

and I don't know what I'm doing wrong.

Solution

You forgot copy haarcascade_frontalface_default.xml and haarcascade_eye.xml files to your working directory.

I think you must download OpenCV https://github.com/opencv/opencv first, those XML files are stored in opencv/data/haarcascades/ folder.

Work for me: