最近在Ubuntu20.04下安装OpenCV3.4.5以及OpenCV_contrib3.4.5时，在生成makefile的时候出现几个错误
1. fatal error: opencv2/xfeatures2d/cuda.hpp: 没有那个文件或目录
In file included from /home/zixuanma/devkits/opencv-3.4.5 /modules /stitching /include /opencv2/stitching.hpp:49,
from /home/zixuanma/devkits/opencv-3.4.5/modules/stitching/src/precomp.hpp:59,
from /home/zixuanma/devkits/opencv-3.4.5/build/modules/stitching/opencv_stitching_ pch_dephelp.cxx:1:
/home/zixuanma/devkits/opencv-3.4.5/modules/stitching/include/opencv2/stitching/detail /matchers.hpp:52:12: fatal error: opencv2/xfeatures2d/cuda.hpp: 没有那个文件或目录
52 | # include "opencv2/xfeatures2d/cuda.hpp"
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
compilation terminated.
解决方法：把路径改为绝对路径就行
（1）根据报错信息中的路径，找到matchers.hpp
/home/zixuanma/devkits/opencv-3.4.5/modules/stitching/include/opencv2/stitching/detail /matchers.hpp:52:12
（2） 定位到52行:
（3）在文件夹搜索栏中搜索cuda.hpp会出现几个结果，根据报错信息选择正确的文件
（4）右键选择打开项目位置
（5）在文件夹中点击在终端打开，可以得到cuda.hpp的上层文件夹路径：
（5）复制下来，补充完成，填写到matchers.hpp的第52行
我的路径是：/home/zixuanma/devkits/opencv-3.4.5/opencv_contrib-3.4.5/modules/xfeatures2d/include/opencv2/xfeatures2d/cuda.hpp
（6）点击保存，重新make，这个问题解决
（7）重新编译，我这里又出现了差不多的错误，方法一样，根据报错信息继续修改就行。
2. fatal error: boostdesc_bgm.i: 没有那个文件或目录
/home/zixuanma/devkits/opencv-3.4.5/opencv_contrib-3.4.5/modules/xfeatures2d/src/boostdesc.cpp:653:20: fatal error: boostdesc_bgm.i: 没有那个文件或目录
653 | #include "boostdesc_bgm.i"
| ^~~~~~~~~~~~~~~~~
compilation terminated.
参考：安装OpenCV时提示缺少boostdesc_bgm.i文件的问题解决方案
虽然我很讨厌在网盘下载这些资源，但是确实解决问题了
主要是也找不到官网
3. fatal error: opencv2/xfeatures2d.hpp: 没有那个文件或目录
/home/zixuanma/devkits/opencv-3.4.5/modules/stitching/src/matchers.cpp:52:10: fatal error: opencv2/xfeatures2d.hpp: 没有那个文件或目录
52 | #include "opencv2/xfeatures2d.hpp"
| ^~~~~~~~~~~~~~~~~~~~~~~~~
compilation terminated.
方法和第一个一样
4. fatal error: opencv2/xfeatures2d/nonfree.hpp: 没有那个文件或目录
In file included from /home/zixuanma/devkits/opencv-3.4.5/modules/stitching/src/matchers.cpp:52:
/home/zixuanma/devkits/opencv-3.4.5/opencv_contrib-3.4.5/modules/xfeatures2d/include/opencv2/xfeatures2d.hpp:43:10: fatal error: opencv2/xfeatures2d/nonfree.hpp: 没有那个文件或目录
43 | #include "opencv2/xfeatures2d/nonfree.hpp"
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
compilation terminated.
方法仍然和第一个相同