opencv+Linux源码编译安装及引用

（一）下载

opencv_contrib下载地址：https://github.com/opencv/opencv_contrib/tags

opencv_contrib是opencv的扩展，主要作用是能够调用GPU进行加速计算，可下载也可不下，且当你GPU性能比较差时反而导致运算速度更慢，两个都要下载源码。

以下以opencv-4.7.0示例。

（二）安装工具及编译

1、依赖库安装

ubuntu等系统通过apt命令安装：

    apt install build-essential cmake git pkg-config libgtk-3-dev \

    libavcodec-dev libavformat-dev libswscale-dev libv4l-dev \

    libxvidcore-dev libx264-dev libjpeg-dev libpng-dev libtiff-dev \

    gfortran openexr libatlas-base-dev python3-dev python3-numpy \

    libtbb2 libtbb-dev libdc1394-22-dev libopenexr-dev \

    libgstreamer-plugins-base1.0-dev libgstreamer1.0-dev

centos、openclouds等系统通过yum命令安装：

yum install cmake gcc gcc-c++ gtk2-devel gtk3-devel gimp-devel gimp-devel-tools gimp-help-browser zlib-devel libtiff-devel libjpeg-devel libpng-devel gstreamer-devel libavc1394-devel libraw1394-devel libdc1394-devel jasper-devel jasper-utils swig python libtool nasm

2、源码安装

解压不多说，解压后将opencv_contrib放入opencv目录中。

cd opencv-4.7.0

mkdir build && cd build

## 构建

cmake -D CMAKE_BUILD_TYPE=RELEASE \

    -D CMAKE_INSTALL_PREFIX=/usr/local \

    -D INSTALL_C_EXAMPLES=ON \

    -D INSTALL_PYTHON_EXAMPLES=ON \

    -D OPENCV_GENERATE_PKGCONFIG=ON \

    -D OPENCV_EXTRA_MODULES_PATH=/usr/local/opencv-4.7.0/opencv_contrib-4.7.0/modules \

    -D BUILD_EXAMPLES=ON ..

在构建代码中CMAKE_INSTALL_PREFIX涉及到之后引用opencv的路径，OPENCV_GENERATE_PKGCONFIG影响pkgconfig的创建，建议填写。

注意：在进行编译过程中，可能会遇到构建程序卡在如下进度：

IPPICV: Downloading ippicv_2020_lnx_intel64_20191018_general.tgz from https://ghproxy.com/https://raw.githubusercontent.com/opencv/opencv_3rdparty/a56b6ac6f030c312b2dce17430eef13aed9af274/ippicv/ippicv_2020_lnx_intel64_20191018_general.tgz

此时需要找到源代码，修改上述下载路径，在路径前加上https://ghproxy.com/。

找到/usr/local/opencv-4.7.0/3rdparty/ippicv，将ippicv.cmake中的下载路径进行修改，如原地址为：

https://ghproxy.com/https://raw.githubusercontent.com/opencv/opencv_3rdparty/${IPPICV_COMMIT}/ippicv/

修改后为：

https://ghproxy.com/https://ghproxy.com/https://raw.githubusercontent.com/opencv/opencv_3rdparty/${IPPICV_COMMIT}/ippicv/

找到/usr/local/opencv-4.7.0/opencv_contrib-4.7.0/modules/wechat_qrcode，打开CMakeList.txt修改下载路径
找到/usr/local/opencv-4.7.0/opencv_contrib-4.7.0/modules/xfeatures2d/cmake，两个cmake都修改

。。。其他的类似，所以说，没GPU加速需求别瞎安装opencv_contrib，找事。

构建完后，开始编译安装

make -j2 && make install

3、环境配置

查看opencv版本信息

pkg-config opencv4 --libs --cflags

如果显示没找到，需要在/etc/profile加入下面配置：

export PKG_CONFIG_PATH=/usr/local/lib64/pkgconfig:$PKG_CONFIG_PATH

最后在/etc/profile加入用于调用的环境变量：

export LD_LIBRARY_PATH=/usr/local/lib64:$LD_LIBRARY_PATH

注意：构建时未配置OPENCV_GENERATE_PKGCONFIG会缺少opencv4.pc文件，导致pkg-config opencv4 --libs --cflags还是不能用

需要手动创建opencv4.pc文件

mkdir /usr/local/lib64/pkgconfig

vim /usr/local/lib64/pkgconfig/opencv4.pc

然后加入以下内容：

# Package Information for pkg-config

prefix=/usr/local

exec_prefix=${prefix}

libdir=${exec_prefix}/lib64

includedir=${prefix}/include/opencv4

Name: OpenCV

Description: Open Source Computer Vision Library

Version: 4.7.0

Libs: -L${exec_prefix}/lib64  -lopencv_stitching  -lopencv_aruco -lopencv_bgsegm -lopencv_bioinspired -lopencv_ccalib -lopencv_dnn_objdetect -lopencv_dnn_superres -lopencv_dpm -lopencv_face -lopencv_freetype -lopencv_fuzzy -lopencv_hfs -lopencv_img_hash -lopencv_intensity_transform -lopencv_line_descriptor -lopencv_mcc -lopencv_quality -lopencv_rapid -lopencv_reg -lopencv_rgbd -lopencv_saliency  -lopencv_stereo -lopencv_structured_light -lopencv_phase_unwrapping -lopencv_superres -lopencv_optflow -lopencv_surface_matching -lopencv_tracking -lopencv_datasets -lopencv_text -lopencv_dnn -lopencv_plot -lopencv_xfeatures2d -lopencv_shape -lopencv_video -lopencv_ml -lopencv_ximgproc -lopencv_calib3d -lopencv_features2d -lopencv_highgui -lopencv_videoio -lopencv_imgcodecs -lopencv_flann -lopencv_photo -lopencv_imgproc -lopencv_core

Libs.private: -ldl -lm -lpthread -lrt

Cflags: -I${includedir}

（三）引用

1.对于Cmake项目，需要在CmakeList.txt中添加以下配置：

# 查找opencv包

find_package(OpenCV REQUIRED)

# 添加头文件目录

include_directories(${OpenCV_INCLUDE_DIRS})

# 链接opencv库，your_executable_or_library表示可执行文件名

target_link_libraries(your_executable_or_library ${OpenCV_LIBS})

2.对于g++、gcc项目，在编译时加上pkg-config opencv4 --libs --cflags，如下：

g++ xxx.cpp -o xxx xxx.cpp  `pkg-config opencv4 --libs --cflags`

3.代码中使用时需要在include中加入如下：

#include<opencv2//opencv.hpp>