Unable to display image after applying LBPH (elbp()) operator in opencv

问题

I am trying to display my input image after applying LBP operator defined in FaceRecognizer class of opencv on it but it only displays pure black image. Does anyone know what I may be doing wrong with my input? I am displaying the image via imshow(). I have also tried to apply elbp() after normalizing my input image but still the same answer. I am using C++.

Input Image (greyscale):

dims = 92x112; depth = CV_8U (I am reading the image via imread())

LBP operator used:

elbp(InputArray _src, OutputArray _dst, int radius, int neighbors) - defined in FaceRecognizer::LBPH class in opencv.

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The other doubt that I have is why the output matrix of function elbp() has lesser no. of rows and columns (strictly: new_rows=rows-2*radius ; new_cols=cols-2*radius). Given radius=1, LBP matrix is of 90x110 dims. Why is that so?

Thanks in advance.

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EDIT This is how image looks like after applying elbp()

And this is how image looks like if I apply olbp(). This is strange.

来源：https://stackoverflow.com/questions/19184358/unable-to-display-image-after-applying-lbph-elbp-operator-in-opencv