open cv error

openCV Error: Assertion failed (!empty()) in detectwultiScale,file /build /opencv-L2vuRj/opencv-3.2.0+dfsg/modules/objdetect/src/cascadedetect.cpp，line 1681[ ERROR][1688269828.941986]: bad callback: <bound nethod faceDetector.inage_callback of ~_main__.faceDetector instance at ox7f02b815a5f0>>Traceback(nost recent call last) :File " /opt/ros/nelodic/lib/python2.7/dist-packages/rospy/topics.py"， line 750，in _invoke_callbackcb(msg)File " /hone/pingan/catkin_ws/src/test1/scripts/face_detector.py" , line 50，in inage_callbackfaces_result = self.detect_face(grey_inage)File "/hone/pingan/catkin_ws/src/test1/scripts/face_detector.py"，line 68,in detect_face( self.haar_minsize, self.haar_naxsize))error: /build/opencv-L2vuNj/opencv-3.2.0+dfsg/nodules/objdetect/src/cascadedetect.cpp:1681: error: (-215) !enpty() in function detectMultiscale

问题点: Cascadedetect错误.
解决方案：

cv::CascadeClassifier face_cascade = cv::CascadeClassifier("/home/opencv/opencv-3.4.4/data/haarcascades/haarcascade_frontalface_default.xml");

参考如下:

https://blog.csdn.net/JIEJINQUANIL/article/details/103037508