前言
本文旨在在ubuntu18.04下安装opencv3.4.1及opencv4.3.0两个版本，进行多版本配置切换，卸载，给出简单的make构造的demo验证安装及qt下对opencv的引入示例。
OpenCV安装
1. OpenCV源码下载
2. 安装命令
cd opencv-3.4.1;
mkdir -p build/installed; cd build;
cmake -DCMAKE_BUILD_TYPE=RELEASE \
-DCMAKE_INSTALL_PREFIX=/home/city945/software/opencv-3.4.1/build/installed \
-DBUILD_TESTS=OFF \
-DOPENCV_GENERATE_PKGCONFIG=ON \
..;
make -j8;
sudo make install;
3. 参数解释
-D CMAKE_INSTALL_PREFIX 指定sudo make install 的安装目录，默认在/usr/local下，如果不改，安装多个版本时，后一版本会覆盖前面版本
-D BUILD_TESTS=OFF 加快编译速度 详细了解 -> https://docs.opencv.org/4.3.0/d7/d9f/tutorial_linux_install.html
-D OPENCV_GENERATE_PKGCONFIG=ON 针对opencv4，使其支持pkg-config
4. 验证安装
查询opencv版本
pkg-config --modversion opencv
pkg-config --cflags opencv
pkg-config --libs opencv
# 注意对opencv4 是 pkg-config --modversion opencv4，可cd /home/city945/software/opencv4.3.0/build/installed/lib/pkgconfig/ 查看
demo 验证 demo源码
多版本配置及切换
.bashrc中控制
# 多版本opencv
# export PKG_CONFIG_PATH="/home/city945/software/opencv-3.4.1/build/installed/lib/pkgconfig"
# export LD_LIBRARY_PATH="/home/city945/software/opencv-3.4.1/build/installed/lib"
export PKG_CONFIG_PATH="/home/city945/software/opencv-4.3.0/build/installed/lib/pkgconfig"
export LD_LIBRARY_PATH="/home/city945/software/opencv-4.3.0/build/installed/lib"
卸载
cd build;
sudo make uninstall;
cd ..; rm -rf build;
# 安装在/usr/local下的手动再把/usr/local/lib下的软连接删了
QT中引入opencv
.pro
INCLUDEPATH += /home/city945/software/opencv-3.4.1/build/installed/include \
/home/city945/software/opencv-3.4.1/build/installed/include/opencv \
/home/city945/software/opencv-3.4.1/build/installed/include/opencv2
LIBS += /home/city945/software/opencv-3.4.1/build/installed/lib/libopencv*.so
参考
opencv-doc Ubuntu下多版本OpenCV共存和切换
2020-07-05
error while loading shared libraries: libopencv_core.so.3.4: cannot open shared object file: No such file or directory
sudo vim /etc/ld.so.conf.d/opencv.conf
# 文件中添加install/lib
/home/city945/software/opencv-3.4.1/build/installed/lib
sudo ldconfig
2020-07-11
CMake Error: The source directory “/home/ssj/opencv-4.3.0/build/OPENCV_GENERATE_PKGCONFIG=ON” does not exist.
-D OPENCV_GENERATE_PKGCONFIG=ON 等参数选项中-D那里不加空格
