ubuntu在编译opencv及opencv_contrib时有时候会报这样的错误：fatal error: opencv2/xfeatures2d/cuda.hpp: No such file or directory，或者opencv2/xfeatures2d.hpp: No such file or directory

        只需要将opencv_contrib-xxx(xxx表示版本号)/modules/xfeatures2d/include/opencv2文件夹下xfeatures2d文件夹和xfeatures2d.hpp文件复制到build/opencv2文件夹中，重新make即可。