python_openCV例程遇到empty() in function cv::CascadeClassifier::detectMultiScale的解决方法

import numpy as np
import cv2

face_cascade=cv2.CascadeClassifier('haarcascade_frontalface_default.xml')
eye_cascade = cv2.CascadeClassifier('haarcascade_eye.xml')
img = cv2.imread('5.jpg')
grey=cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)

faces = face_cascade.detectMultiScale(grey, 1.3, 5)
for (x,y,w,h) in faces:
    cv2.rectangle(img,(x,y),(x+w,y+h),(255,0,0),2)
    roi_gray = grey[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()

注意点有：

1.haarcascade_frontalface_default.xml  haarcascade_eye.xml 这两个文件必须要引入 文件地址https://github.com/opencv/opencv/blob/master/data/haarcascades/haarcascade_eye.xml

2.图片路径和文件路径一定要正确，报错一般都是文件名或者路径不正确