Pycharm does not show image preview on macOS "Big Sur" using OpenCV and Python3.9

Question

I'm trying to code a face recognition app using OpenCV and python on macOS 'Big Sur' and Pycharm, but unfortunately it does not show the image window/preview and it does not show any errors in console , below you can check code:

import cv2

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

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

gray_img = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)

face = face_cascade.detectMultiScale(gray_img,
                                     scaleFactor=1.05, minNeighbors=5)

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

resized = cv2.resize(img, (int(img.shape[1]/3), int(img.shape[0]/3)))

# cv2.startWindowThread()
# cv2.namedWindow("preview")
cv2.imshow('preview', img)
cv2.waitKey(0)
cv2.destroyWindow('preview')

I have tried adding cv2.startWindowThread(), cv2.namedWindow("preview") and even installed headless by "pip3 install opencv-python-headless" but it does not work.

Answer 1

Replace the line face_cascade = cv2.CascadeClassifier('haarcascade_frontalface_default.xml')

with face_cascade = cv2.CascadeClassifier(cv2.data.haarcascade + 'haarcascade_frontalface_default.xml')

and then it should work fine

Here's the final code :

import cv2

face_cascade = cv2.CascadeClassifier(cv2.data.haarcascade + 'haarcascade_frontalface_default.xml')

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

gray_img = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)

face = face_cascade.detectMultiScale(gray_img,
                                     scaleFactor=1.05, minNeighbors=5)

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

resized = cv2.resize(img, (int(img.shape[1]/3), int(img.shape[0]/3)))

# cv2.startWindowThread()
# cv2.namedWindow("preview")
cv2.imshow('preview', img)
cv2.waitKey(0)
cv2.destroyWindow('preview')