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源代码是：

import cv2

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

eye_cascade = cv2.CascadeClassifier(cv2.data.haarcascades+'haarcascade_eye.xml')

cap = cv2.VideoCapture(0)

while(True):

    ret, frame = cap.read()
    faces = face_cascade.detectMultiScale(frame, 1.3, 5)
    img = frame
    for (x,y,w,h) in faces:

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

        face_area = img[y:y+h, x:x+w]
        eyes = eye_cascade.detectMultiScale(face_area)

        for (ex,ey,ew,eh) in eyes:

            cv2.rectangle(face_area,(ex,ey),(ex+ew,ey+eh),(0,255,0),1)


    cv2.imshow('frame2',img)

    if cv2.waitKey(5) & 0xFF == ord('q'):
        break


cap.release()
cv2.destroyAllWindows()

结果报错：

faces = face_cascade.detectMultiScale(frame, 1.3, 5)
cv2.error: OpenCV(4.4.0) C:\Users\appveyor\AppData\Local\Temp\1\pip-req-build-h4wtvo23\opencv\modules\objdetect\src\cascadedetect.cpp:1689: error: (-215:Assertion failed) !empty() in function 'cv::CascadeClassifier::detectMultiScale'

[ WARN:0] global C:\Users\appveyor\AppData\Local\Temp\1\pip-req-build-h4wtvo23\opencv\modules\videoio\src\cap_m喵f.cpp (435) `anonymous-namespace'::SourceReaderCB::~SourceReaderCB terminating async callback

 

路径全英文，要用的文件也都放在一个文件夹里，怎么回事