记一次非常捉鸡的OpenCV安装过程

由于换电脑、重装系统、系统奔溃、换固态，不到一年已经重装OpenCV不下十次了，本以为装了这么多次应该没什么问题了，可最奔溃的是几乎每次都会出错，而且出的错每次都不一样，心疼自己。。。把这次出现的问题记录一下。

0. 环境

ubuntu14.04
opencv3.3.1
opencv_contrib-3.3.1

---

1. 第一次出错

1.1 make提示

Failed to download tiny-dnn sources
> -- Looking for tiny_dnn.h
> -- Looking for tiny_dnn.h - not found
> -- Module opencv_dnn_modern disabled because tiny-dnn was not found
> -- checking for one of the modules 'freetype2'
> -- checking for one of the modules 'harfbuzz'
> -- freetype2:   NO
> -- harfbuzz:    NO
> -- Could NOT find HDF5 (missing:  HDF5_LIBRARIES HDF5_INCLUDE_DIRS) 
> -- No preference for use of exported gflags CMake configuration set, and no hints for include/library directories provided. Defaulting to preferring an installed/exported gflags CMake configuration if available.
> -- Failed to find installed gflags CMake configuration, searching for gflags build directories exported with CMake.
> -- Failed to find gflags - Failed to find an installed/exported CMake configuration for gflags, will perform search for installed gflags components.
> -- Failed to find gflags - Could not find gflags include directory, set GFLAGS_INCLUDE_DIR to directory containing gflags/gflags.h
> -- Failed to find glog - Could not find glog include directory, set GLOG_INCLUDE_DIR to directory containing glog/logging.h
> -- Module opencv_sfm disabled because the following dependencies are not found: Eigen Glog/Gflags
> -- checking for modules 'tesseract;lept'
> --   package 'tesseract' not found
> --   package 'lept' not found
> -- Tesseract:   NO
> -- xfeatures2d/boostdesc: Download: boostdesc_bgm.i
> CMake Warning at  ~/workspace/opencv/opencv-master/cmake/OpenCVDownload.cmake:170 (message):
>   xfeatures2d/boostdesc: Download failed: 1;"Unsupported protocol"
> Call Stack (most recent call first):
>    ~/workspace/opencv_contrib-master/modules/xfeatures2d/cmake/download_boostdesc.cmake:22 (ocv_download)
>   ~/workspace/opencv_contrib-master/modules/xfeatures2d/CMakeLists.txt:8 (download_boost_descriptors)

1.2 make报错

In file included from ~/workspace/opencv/opencv-master/modules/stitching/include/opencv2/stitching.hpp:49:0,
                 from ~/workspace/opencv/opencv-master/modules/stitching/src/precomp.hpp:59,
                 from ~/workspace/build/modules/stitching/opencv_stitching_pch_dephelp.cxx:1:
~/workspace/opencv/opencv-master/modules/stitching/include/opencv2/stitching/detail/matchers.hpp:52:42: fatal error: opencv2/xfeatures2d/cuda.hpp: No such file or directory
 #  include "opencv2/xfeatures2d/cuda.hpp"
                                          ^

1.3 尝试

①看了cmake时的提示，估计是opencv_contrib-3.3.1/modules/dnn_modern 中文件下载出错，于是参考网上的方法离线下载放入对应的路径中，但还是没有解决。又怀疑是网络问题更换了国外的源，并启用了代理，也是没有下载成功。

②又根据make时报错的提示，想可能时cuda的因素，尝试不启用也没有解决。

1.4 解决1

cmake过程中会下载很多需要的文件，没有下载成功也不会报错，所以没注意的话一般就直接执行下一步了，然后make时报错，通常根据make时的提示寻找问题，但其实根源是在cmake时出现的，所以先解决cmake的问题。

参考github上的issue：https://github.com/opencv/opencv_contrib/issues/1131
有网友根据提示Download failed: 1;"unsupported protocol"认为是因为下载出错引起的，所用的cmake版本没有支持HTTPS，于是重新安装了cmake（之前用的时3.11版本，然后卸载按下面的方式安装了3.9.0）

wget --no-check-certificate https://cmake.org/files/v3.9/cmake-3.9.0.tar.gz
tar -zxvf cmake-3.9.0.tar.gz
cd cmake-3.9.0
sudo apt-get install libcurl4-gnutls-dev
sudo apt-get install zlib1g-dev
./bootstrap --system-curl
sudo make && sudo make install

安装完之后然后重新cmake，cmake两遍看出现的问题2（第一遍出错时信息太多，没显示出错的地方，cmake第二遍）
（安装支持HTTPS的cmake不是直接解决问题，而是可以更清楚地看问题的根源）

---

2. 第二次出错

2.1 cmake报错

Invalid escape sequence \,
Call Stack (most recent call first):
  /home/tank/Programming/opencv/cmake/OpenCVDownload.cmake:162 (ocv_download_log)
  /home/tank/Programming/opencv_contrib/modules/xfeatures2d/cmake/download_boostdesc.cmake:22 (ocv_download)
  /home/tank/Programming/opencv_contrib/modules/xfeatures2d/CMakeLists.txt:8 (download_boost_descriptors)


-- Configuring incomplete, errors occurred!
See also "/home/tank/Programming/opencv/build/CMakeFiles/CMakeOutput.log".
See also "/home/tank/Programming/opencv/build/CMakeFiles/CMakeError.log".

2.2 解决

Github上有网友指出是因为OpenCVDownload.cmake在日志记录功能中出现问题，找到文件～/opencv-3.3.1/cmake/OpenCVDownload.cmake
将以下代码

  macro(ocv_download_log)
    file(APPEND "${OPENCV_DOWNLOAD_LOG}" "${ARGN}\n")
  endmacro()

修改成

  function(ocv_download_log)
    file(APPEND "${OPENCV_DOWNLOAD_LOG}" "${ARGN}\n")
  endfunction()

然后重新cmake，make，make install 成功。