File "C:/Users/zzx/PycharmProjects/pythonProject1/face-recognize.py", line 17, in
gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
cv2.error: OpenCV(4.5.3) C:\Users\runneradmin\AppData\Local\Temp\pip-req-build-u4kjpz2z\opencv\modules\imgproc\src\color.cpp:182: error: (-215:Assertion failed) !_src.empty() in function 'cv::cvtColor'
[ WARN:1] global C:\Users\runneradmin\AppData\Local\Temp\pip-req-build-u4kjpz2z\opencv\modules\videoio\src\cap_msmf.cpp (438) `anonymous-namespace'::SourceReaderCB::~SourceReaderCB terminating async callback
看一下 原始图像img是不是 3通道图像
print(img.shape)
!_src.empty()看到这个报错就检查一下图片，一般这个报错都是路径问题导致你的图片是空的，检查一下图片路径吧