OpenCV shape_example

I know the ShapeContextDistanceExtractorImpl::computeDistance(InputArray contour1, in sc_dis.cpp, and I have tried the exmaple of “OpenCV shape_example”, But I does not know the algorithm。Can anyone give me an annotation of the function. Or specify document of the function. thanks!

May be this

Implementation of the Shape Context descriptor and matching algorithm.

proposed by Belongie et al. in “Shape Matching and Object Recognition Using Shape Contexts” (PAMI 2002). This implementation is packaged in a generic scheme, in order to allow you the implementation of the common variations of the original pipeline.