其实，我们使用的opencv中要用的contrib/modules 是需要额外下载并在cmakelists.txt中指定的
git clone https://github.com/opencv/opencv_contrib.git 然后，就有opencv_contrib 的path啦
CMake Error at cmake/OpenCVModule.cmake:295 (message): No extra modules found in folder:Please provide path to 'opencv_contrib/modules' folder
原文：http://www.cnblogs.com/YouXiangLiThon/p/7199241.html
