What is InputArray?

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This is the proxy class for passing read-only input arrays into OpenCV functions.

Inside a function you should use _InputArray::getMat() method to construct a matrix header for the array (without copying data). _InputArray::kind() can be used to distinguish Mat from vector<> etc., but normally it is not needed.

More information you can find here: http://docs.opencv.org/modules/core/doc/basic_structures.html?highlight=inputarray#InputArray