opencv4.4.0下载地址：https://sourceforge.net/projects/opencvlibrary/files/
问题描述
安装完opencv4.4.0后编译C++代码显示找不到lib库文件

/usr/bin/ld: cannot find -lopencv_shape
/usr/bin/ld: cannot find -lopencv_stitching
/usr/bin/ld: cannot find -lopencv_objdetect
/usr/bin/ld: cannot find -lopencv_superres
/usr/bin/ld: cannot find -lopencv_videostab
/usr/bin/ld: cannot find -lopencv_calib3d
/usr/bin/ld: cannot find -lopencv_features2d
/usr/bin/ld: cannot find -lopencv_highgui
/usr/bin/ld: cannot find -lopencv_videoio
/usr/bin/ld: cannot find -lopencv_imgcodecs
/usr/bin/ld: cannot find -lopencv_video
/usr/bin/ld: cannot find -lopencv_photo
/usr/bin/ld: cannot find -lopencv_ml
/usr/bin/ld: cannot find -lopencv_imgproc
/usr/bin/ld: cannot find -lopencv_flann
/usr/bin/ld: cannot find -lopencv_core
collect2: error: ld returned 1 exit status

查看后台运行程序
ps

一、安装opencv依赖库

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-is-python2 python-numpy libtbb2 libtbb-dev libjpeg-dev libpng-dev libtiff-dev libdc1394-22-dev libjasper-dev（libjasper-dev依赖包可能找不到，参考博客）
sudo apt-get install libavcodec-dev libavformat-dev libswscale-dev libv4l-dev liblapacke-dev
sudo apt-get install libxvidcore-dev libx264-dev
sudo apt-get install libatlas-base-dev gfortran
sudo apt-get install ffmpeg

二、opencv编译安装

2.1 sudo cmake-gui
设置路径如下，点击configure，编译器使用默认即可

之后，修改两处地方，再点击generate

1. 勾选上BUILD_opencv_world
2. 在CMAKE_BUILD_TYPE后填上：RELEASE

如果有需要用到OpenCV contrib组件的，需要在OPENCV_EXTRA_MODULES_PATH后填上opencv-contrib/modules的路径

2.2编译
进入build文件夹，可以发现Makefile文件，输入sudo make开始编译

2.3安装
输入指令 sudo make install
2.4路径配置

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

打开文件输入/usr/local/lib

执行生效指令sudo ldconfig
编辑sudo gedit /etc/bash.bashrc
输入export PKG_CONFIG_PATH=$PKG_CONFIG_PATH:/usr/local/lib/pkgconfig
使环境变量生效source /etc/bash.bashrc
opencv4.4.0到此安装完成，但由于opencv4.4.0默认不生成opencv.pc，所以此时查看opencv版本会报错
查看opencv版本 指令：pkg-config opencv --modversion

解决方法：

cd /usr/local/lib
sudo mkdir pkgconfig
cd pkgconfig
sudo gedit opencv.pc

输入

prefix=/usr/local
exec_prefix=${prefix}
includedir=${prefix}/include
libdir=${exec_prefix}/lib

Name: opencv
Description: The opencv library
Version:4.4.0
Cflags: -I${includedir}/opencv4
Libs: -L${libdir} -lopencv_shape -lopencv_stitching -lopencv_objdetect -lopencv_superres -lopencv_videostab -lopencv_calib3d -lopencv_features2d -lopencv_highgui -lopencv_videoio -lopencv_imgcodecs -lopencv_video -lopencv_photo -lopencv_ml -lopencv_imgproc -lopencv_flann  -lopencv_core
~                                               

可能遇到的问题

用上文安装方法一直很顺利，可在测试程序时，还是出了点问题，如下，显示找不到lib库

这种问题的原因我也不太清楚，但我感觉应该是因为opencv4.4.0编译生成opencv4而不叫opencv，所以导致找不到
解决方法：
进入build文件夹，重新编译了一遍opencv，指令如下

sudo make uninstall
sudo cmake -DCMAKE_BUILD_TYPE=Release -DOPENCV_GENERATE_PKGCONFIG=ON -DCMAKE_INSTALL_PREFIX=/usr/local ..
sudo make
sudo make install

注：opencv4默认不生成opencv4.pc，指令-DOPENCV_GENERATE_PKGCONFIG=ON
可以生成opencv4.pc

把上文在/usr/local/lib/pkgconfig底下建的opencv.pc先删除，输入pkg-config opencv4 --modversion，可以看到版本信息，而输入pkg-config opencv --modversion却报错，这时候编译测试代码，却发现找不到opencv

因此，我在底下复制了一份opencv4.pc，改名为opencv.pc，此时运行代码就不报错了。

所以我感觉还是opencv的名称有问题，如果按上文方法安装完成后，直接在/usr/local/lib/pkgconfig底下建一个opencv4.pc应该就不报错的（我猜的，没试过）

附：测试代码

sudo g++ -std=c++11 `pkg-config opencv --cflags` opencvtest.cpp -o opencv `pkg-config opencv --libs` 

opencvtest.cpp

#include <iostream>
#include <opencv2/opencv.hpp>
 
using namespace std;
using namespace cv;
 
int main()
{
    Mat srcImage = imread("lena.jpg");
    imshow("源图像",srcImage);
 
    waitKey(0);
 
    return 0;
}

参考博客
在Linux下用正确的姿势安装OpenCV
Package opencv was not found in the pkg-config search path