OpenCV 4.7.0: SystemError: <class 'cv2.CascadeClassifier'> returned a result with an exception set

Question

This is the beginning of the code. I am following a face recognition project tutorial using OpenCV and Python. This is meant to take a picture of a face using haar cascade face detection and then storing in a dataset file I have.

import cv2
import os

cam = cv2.VideoCapture(0)
cam.set(3, 640) # set video width
cam.set(4, 480) # set video height


face_detector = cv2.CascadeClassifier('/Users/*********/workspace/Facial Recognition Project/haarcascade_frontalface_default.xml')

# For each person, enter one numeric face id
face_id = input('\n enter user id end press <return> ==>  ')

print("\n [INFO] Initializing face capture. Look the camera and wait ...")
# Initialize individual sampling face count
count = 0

while(True):

    ret, img = cam.read()
    img = cv2.flip(img, -1) # flip video image vertically
    gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
    faces = face_detector.detectMultiScale(gray, 1.3, 5)

    for (x,y,w,h) in faces:

        cv2.rectangle(img, (x,y), (x+w,y+h), (255,0,0), 2)     
        count += 1

        # Save the captured image into the datasets folder
        cv2.imwrite("dataset/User." + str(face_id) + '.' + str(count) + ".jpg", gray[y:y+h,x:x+w])

        cv2.imshow('image', img)

    k = cv2.waitKey(100) & 0xff # Press 'ESC' for exiting video
    if k == 27:
        break
    elif count >= 30: # Take 30 face sample and stop video
         break

# Do a bit of cleanup
print("\n [INFO] Exiting Program and cleanup stuff")
cam.release()
cv2.destroyAllWindows()```

This was the error:

cv2.error: OpenCV(4.7.0) /Users/opencv-cn/GHA-OCV-1/_work/opencv-python/opencv-python/opencv/modules/core/src/persistence.cpp:681: error: (-215:Assertion failed) buf in function 'open'

The above exception was the direct cause of the following exception:

Traceback (most recent call last): File "/Users/sashuponnaganti/workspace/Facial Recognition Project/01_face_dataset.py", line 9, in face_detector = cv2.CascadeClassifier('/Users/*********/workspace/Facial Recognition Project/haarcascade_frontalface_default.xml') SystemError: <class 'cv2.CascadeClassifier'> returned a result with an exception set

I believe that I am using the cv2.CascadeClassifier function correctly and I know the filepath for the xml file is correct so I am confused why I am getting an error.

Answer 1

I guess you don't need to enforce cv2 to find xml at some particular path... So, try to use

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

insted.