Where can I download the mingw libraries for opencv
i.e. the libraries that should be in folder: c:\opencv\build\x64\mingw\lib. Only the VC12 and VC14 libraries are available in OpenCV3.1.0
Is there an alternative to compiling them (i.e. https://zahidhasan.wordpress.com/2013...)
you will have to build from src, there is absolutely no alternative.