[人工智能]ubuntu18安装opencv3.4.0+opencv_contrib3.4.0

1.下载opencv3.4.0及opencv3.4.0_contrib

opencv和opencv_contrib下载地址：

https://github.com/opencv/opencv/releases
https://github.com/opencv/opencv_contrib/releases

将opencv3.4.0及opencv3.4.0_contrib解压，将opencv3.4.0_contrib的文件夹放到opencv3.4.0的文件夹中.

2.编译安装opencv

(1).安装依赖

sudo apt-get install build-essential 
sudo apt-get install cmake git libgtk2.0-dev pkg-config libavcodec-dev libavformat-dev libswscale-dev
sudo apt-get install python-dev python-numpy libtbb2 libtbb-dev libjpeg-dev libpng-dev libtiff-dev libjasper-dev libdc1394-22-dev

如果有报错说libjaster-dev无法安装，解决办法如下：

sudo add-apt-repository "deb http://security.ubuntu.com/ubuntu xenial-security main"
sudo apt update
sudo apt install libjasper1 libjasper-dev

(2).新建build文件夹进行编译

先设置路径文件：

sudo mkdir /usr/local/opencv3.4.0

在解压的opencv3.4.0文件下新建build文件夹并打开执行：

cmake -DOPENCV_EXTRA_MODULES_PATH=/home/xxx/opencv-3.4.0/opencv_contrib-3.4.0/modules -DBUILD_opencv_legacy=OFF /home/xxx/opencv-3.4.0 -D ENABLE_PRECOMPILED_HEADERS=OFF -D CMAKE_BUILD_TYPE=RELEASE -D CMAKE_INSTALL_PREFIX=/usr/local/opencv3.4.0 -D WITH_TBB=ON -D BUILD_NEW_PYTHON_SUPPORT=ON -D WITH_V4L=ON -D WITH_QT=ON -D WITH_OPENGL=ON ..

注意： 上面-D OPENCV_EXTRA_MODULES_PATH路径需要改成自己opencv_contrib下modules 的路径

其实，可以认真阅读opencv_contrib下README.md的解释：

$ cd <opencv_build_directory>
$ cmake -DOPENCV_EXTRA_MODULES_PATH=<opencv_contrib>/modules <opencv_source_directory>
$ make -j5

在执行make时会有以下报错和解决方法：

报错1：

Could not find a package configuration file provided by "Qt5Concurrent"with any of the following names:
    Qt5ConcurrentConfig.cmake
    qt5concurrent-config.cmake

解决：sudo apt-get install libqglviewer-dev-qt5

报错2：

ICV: Failed to download ICV package: ippicv_linux_20151201.tgz.

解决：网速不行，自行下载ippicv_linux_20151201.tgz(博客上一大堆下载地址)并替换./opencv-3.4.0/3rdparty/ippicv/downloads/linux-808b791a6eac9ed78d32a7666804320e下的文件.

报错3：

fatal error: boostdesc_bgm.i: 没有那个文件或目录
           #include "boostdesc_bgm.i"

解决：https://blog.csdn.net/u011736771/article/details/85960300，下载你缺失的文件，并放到~/opencv_contrib/modules/xfeatures2d/src/下.

报错4：

fatal error: opencv-3.4.0/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
 #  include "opencv2/xfeatures2d/cuda.hpp

解决：找到matchers.hpp文件，将对应的头文件地址修改为绝对路径：
/home/xxx/opencv-3.4.0/opencv_contrib-3.4.0/modules/xfeatures2d/include/opencv2/xfeatures2d/cuda.hpp
以及在opencv-3.4.0/modules/stitching的cmakelists添加绝对路径：
INCLUDE_DIRECTORIES("/home/xxx/opencv-3.4.0/opencv_contrib-3.4.0/modules/xfeatures2d/include")

最后：

make -j4
sudo make install

3.配置OpenCV的编译环境

目的是让系统找到OpenCV的库的路径，打开编写一个空白的文件opencv.conf:

sudo gedit /etc/ld.so.conf.d/opencv.conf 

在opencv.conf中添加如下内容:

/usr/local/opencv3.4.0/lib 

保存并关闭文件，使刚配置路径生效：

sudo ldconfig  

打开bash文件，配置bash：

sudo gedit /etc/bash.bashrc  

在打开的bash.bashrc的最末尾添加如下代码：

export PKG_CONFIG_PATH=$PKG_CONFIG_PATH:/usr/local/opencv3.4.0/lib/pkgconfig  
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/local/opencv3.4.0/lib

保存关闭文件，使刚才的配置生效：

source /etc/bash.bashrc 

用一个小程序测试一下
到opencv-3.4.0/samples/cpp/example_cmake目录下
我们可以看到这个目录里官方已经给出了一个cmake的example我们可以拿来测试下

cmake .
make
./opencv_example

如果成功运行了电脑摄像头则安装成功.