OpenCV Background subtraction 3.2 version example (for MOG, MOG2, GMG, KNN)

This is example for background subtraction on opencv 3.2 version

previously, I post 2.7 version example on here.
http://study.marearts.com/2014/04/opencv-study-background-subtractor-mog.html

But some usage is changed, and knn subtraction method is added.

Many people ask that example based on opencv 3.2

refer to below source code

Thank you.

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