使用open cv在python中处理图像

Question

import cv2 
fc=cv2.CascadeClassifier("haarcascade_fontalface_default.xml")

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

faces= fc.detectMultiScale(gray,1.1,4)

for (x,y,w,h) in faces:
    cv2.rectangle(img, (x,y), (x+w,y+h),(0,255,0),2)
    
cv2.imshow('img',img)
cv2.waitkey()

---------------------------------------------------------------------------
error                                     Traceback (most recent call last)
<ipython-input-3-9ba3354eb85a> in <module>
      3 
      4 img=cv2.imread('dp.jpg')
----> 5 gray=cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)
      6 
      7 faces= fc.detectMultiScale(gray,1.1,4)

error: OpenCV(4.4.0) C:\Users\appveyor\AppData\Local\Temp\1\pip-req-build-rwld3ghi\opencv\modules\imgproc\src\color.cpp:182: error: (-215:Assertion failed) !_src.empty() in function 'cv::cvtColor'

Answer 1

Below are the possible reasons for the error

• Give full path for your haar cascade file

• Give the full path for your image . Check whether cv2 as correctly read your image by using print(img) , if it returns None then the path specified by you is incorrect . Correct your path and try printing the image, if an array shows up then you are well to go as your image is now read successfully