在一个只有ubuntu20.04的docker环境中配置opencv4.0.0,
什么库都没有，都要重新安装，
其他的问题在网上都找到了解决方案，唯独这个问题比较棘手：
86%\] Linking CXX executable .../.../bin/opencv_annotation /usr/bin/ld: /usr/local/lib/libgflags.a(gflags.cc.o): relocation R_X86_64_PC32 against symbol \`stderr@@GLIBC_2.2.5' can not be used when making a shared object; recompile with -fPIC /usr/bin/ld: final link failed: bad value collect2: error: ld returned 1 exit status make\[2\]: \[modules/sfm/CMakeFiles/opencv_sfm.dir/build.make:243: lib/libopencv_sfm.so.4.0.0\] Error 1 make\[1\]: \[CMakeFiles/Makefile2:12239: modules/sfm/CMakeFiles/opencv_sfm.dir/all\] Error 2 我看出是编译libopencv_sfm.so时出的问题，也看出需要用-fPIC重新编译gflags ```bash # 1. 首先清理之前的安装 sudo apt remove libgflags-dev cd ~/gflags rm -rf build cmake -DCMAKE_BUILD_TYPE=Release \ -DBUILD_SHARED_LIBS=ON \ -DCMAKE_CXX_FLAGS="-fPIC" \ -DCMAKE_C_FLAGS="-fPIC" \ -DCMAKE_INSTALL_PREFIX=/usr/local \ .. # 3. 编译和安装 make -j$(nproc) sudo make install sudo ldconfig ``` 编译好之后再重新build opencv, 注意我是在root权限下，不是root的前面都加上sudo ```bash cd ~/opencv/build cmake -D CMAKE_BUILD_TYPE=Release -D CMAKE_INSTALL_PREFIX=/usr/local/opencv4.0.0 -D OPENCV_EXTRA_MODULES_PATH=~/opencv_contrib-4.0.0/modules -D BLAS_LIBRARIES=/usr/lib/x86_64-linux-gnu/libblas.so -D LAPACK_LIBRARIES=/usr/lib/x86_64-linux-gnu/liblapack.so .. make -j8 make install #更新系统的动态链接库缓存 ldconfig sudo nano ~/.bashrc # 在文件末尾添加以下内容 # 根据自己的安装路径来，我是cmake时指定了安装在/usr/local/opencv4.0.0 export OpenCV_DIR=/usr/local/opencv4.0.0 export PATH=$PATH:$OpenCV_DIR/bin export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$OpenCV_DIR/lib export PKG_CONFIG_PATH=$PKG_CONFIG_PATH:$OpenCV_DIR/lib/pkgconfig export CPATH=$CPATH:$OpenCV_DIR/include/opencv4 # 保存并退出（在nano中按Ctrl+X，然后按Y确认，最后按Enter） #用vi也行 # 使环境变量生效 source ~/.bashrc ``` 为了确保pkg-config能正确找到OpenCV，还需要创建或修改pkg-config文件： ```bash # 如果pkg-config文件夹不存在，创建它 sudo mkdir -p /usr/local/opencv4.0.0/lib/pkgconfig # 创建opencv4.pc文件 sudo nano /usr/local/opencv4.0.0/lib/pkgconfig/opencv4.pc #添加以下内容 prefix=/usr/local/opencv4.0.0 exec_prefix=${prefix} includedir=${prefix}/include libdir=${prefix}/lib Name: OpenCV Description: Open Source Computer Vision Library Version: 4.0.0 Cflags: -I${includedir} Libs: -L${libdir} -lopencv_core -lopencv_imgproc -lopencv_highgui -lopencv_ml -lopencv_video -lopencv_features2d -lopencv_calib3d -lopencv_objdetect -lopencv_flann ``` 最后验证安装： ```bash # 检查环境变量是否设置成功 echo $LD_LIBRARY_PATH echo $PKG_CONFIG_PATH # 检查OpenCV是否能被找到 pkg-config --modversion opencv4 ```