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Unable to use lbpcascade for facial detection in python

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I have been trying to use the lbpcascade approach to detecting faces using the JeVois camera. I have been following the tutorial from the link below, but I can't seem to transfer the code over to the camera without it crashing. The main error it gives me is "(-215) !empty() in function detectmultiscale", and I have been told that this means you don't have the correct file path in the calling of "detectmultiscale". However I feel that my file paths are sound.

        face_cascade = cv2.CascadeClassifier('jevois/share/facedetector/lbpcascade_frontalface.xml')
        gray = cv2.imread("jevois/share/facedetector/rooster.jpg")
        faces = face_cascade.detectMultiScale(gray, 1.2, 5);
 

These are the lines of code in question, and I have added the "lbpcascade_frontalface.xml" in correct directory, as well as the "rooster.jpg". Any help for how to accomplish facial detection in python with the JeVois camera specifically would be much appreciated. I say specifically because my problem lies in the altering of the code from online tutorials, to make it compatible with the JeVois camera. So I don't feel that links to tutorials that teach you how to do facial detection with other hardware will be of much use to me. Thank you for your time!

asked Mar 20, 2018 in Programmer Questions by hamac2003 (400 points)

1 Answer

+1 vote
 
Best answer
Can you confirm that your paths are ok, for example by first writing a python module that does the cv2.imread() as you do it and then writes a string on the output image with the dimensions of the resulting image? You would just modify the PythonSandbox module to add that imread command. It seems that maybe you should add a leading / to all your paths to make them absolute:

/jevois/share/...

Looking for your error message on google leads to this:

https://stackoverflow.com/questions/30508922/error-215-empty-in-function-detectmultiscale

which also suggests a path issue.
answered Mar 20, 2018 by JeVois (39,960 points)
selected Mar 21, 2018 by hamac2003
Thank you for your help! I changed the file paths from "jevois/share" to "/jevois/share", and that fixed my problem.
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