1 编译

        opencv的编译总体来说比较简单，但必须记住一点：opencv的版本必须和opencv_contrib的版本保持一致。例如opencv使用4.8.0，opencv_contrib也必须使用4.8.0。

        进入opencv和opencv_contrib的github页面后，默认看到的是git分支，如4.x。

        如果想要下载具体的版本，需要通过tag进行查找。

        注意，一定要下载具体的tag进行编译，不要选择branch，否则编译会报错。如opencv选择4.8.0，opencv_contrib选择4.x，编译会报下面的错误：

/Users/Github/opencv-4.8.0/modules/core/include/opencv2/core/hal/intrin_sse.hpp:1437:1: note: candidate function template not viable: requires single argument 'a', but 2 arguments were provided
OPENCV_HAL_IMPL_SSE_SHIFT_OP(v_uint16x8, v_int16x8, epi16, _mm_srai_epi16)
^
/Users/Github/opencv-4.8.0/modules/core/include/opencv2/core/hal/intrin_sse.hpp:1427:16: note: expanded from macro 'OPENCV_HAL_IMPL_SSE_SHIFT_OP'
inline _Tpuvec v_shr(const _Tpuvec& a) \^
/Users/Github/opencv-4.8.0/modules/core/include/opencv2/core/hal/intrin_sse.hpp:1437:1: note: candidate function template not viable: requires single argument 'a', but 2 arguments were provided
/Users/Github/opencv-4.8.0/modules/core/include/opencv2/core/hal/intrin_sse.hpp:1432:16: note: expanded from macro 'OPENCV_HAL_IMPL_SSE_SHIFT_OP'
inline _Tpsvec v_shr(const _Tpsvec& a) \^
/Users/Github/opencv-4.8.0/modules/core/include/opencv2/core/hal/intrin_sse.hpp:1438:1: note: candidate function template not viable: requires single argument 'a', but 2 arguments were provided
OPENCV_HAL_IMPL_SSE_SHIFT_OP(v_uint32x4, v_int32x4, epi32, _mm_srai_epi32)
^
/Users/Github/opencv-4.8.0/modules/core/include/opencv2/core/hal/intrin_sse.hpp:1427:16: note: expanded from macro 'OPENCV_HAL_IMPL_SSE_SHIFT_OP'
inline _Tpuvec v_shr(const _Tpuvec& a) \^
/Users/Github/opencv-4.8.0/modules/core/include/opencv2/core/hal/intrin_sse.hpp:1438:1: note: candidate function template not viable: requires single argument 'a', but 2 arguments were provided
/Users/Github/opencv-4.8.0/modules/core/include/opencv2/core/hal/intrin_sse.hpp:1432:16: note: expanded from macro 'OPENCV_HAL_IMPL_SSE_SHIFT_OP'
inline _Tpsvec v_shr(const _Tpsvec& a) \^
/Users/Github/opencv-4.8.0/modules/core/include/opencv2/core/hal/intrin_sse.hpp:1439:1: note: candidate function template not viable: requires single argument 'a', but 2 arguments were provided
OPENCV_HAL_IMPL_SSE_SHIFT_OP(v_uint64x2, v_int64x2, epi64, v_srai_epi64)
^
/Users/Github/opencv-4.8.0/modules/core/include/opencv2/core/hal/intrin_sse.hpp:1427:16: note: expanded from macro 'OPENCV_HAL_IMPL_SSE_SHIFT_OP'
inline _Tpuvec v_shr(const _Tpuvec& a) \^
/Users/Github/opencv-4.8.0/modules/core/include/opencv2/core/hal/intrin_sse.hpp:1439:1: note: candidate function template not viable: requires single argument 'a', but 2 arguments were provided
/Users/Github/opencv-4.8.0/modules/core/include/opencv2/core/hal/intrin_sse.hpp:1432:16: note: expanded from macro 'OPENCV_HAL_IMPL_SSE_SHIFT_OP'
inline _Tpsvec v_shr(const _Tpsvec& a) \^
/Users/Github/opencv_contrib-4.x/modules/xphoto/src/grayworld_white_balance.cpp:290:21: error: no matching function for call to 'v_shr'v_sR2 = v_shr(v_mul_wrap(v_sR2, v_gainR), 8);^~~~~
/Users/Github/opencv-4.8.0/modules/core/include/opencv2/core/hal/intrin_sse.hpp:1437:1: note: candidate function template not viable: requires single argument 'a', but 2 arguments were provided
OPENCV_HAL_IMPL_SSE_SHIFT_OP(v_uint16x8, v_int16x8, epi16, _mm_srai_epi16)
^
/Users/Github/opencv-4.8.0/modules/core/include/opencv2/core/hal/intrin_sse.hpp:1427:16: note: expanded from macro 'OPENCV_HAL_IMPL_SSE_SHIFT_OP'
inline _Tpuvec v_shr(const _Tpuvec& a) \^
/Users/Github/opencv-4.8.0/modules/core/include/opencv2/core/hal/intrin_sse.hpp:1437:1: note: candidate function template not viable: requires single argument 'a', but 2 arguments were provided
/Users/Github/opencv-4.8.0/modules/core/include/opencv2/core/hal/intrin_sse.hpp:1432:16: note: expanded from macro 'OPENCV_HAL_IMPL_SSE_SHIFT_OP'
inline _Tpsvec v_shr(const _Tpsvec& a) \^
/Users/Github/opencv-4.8.0/modules/core/include/opencv2/core/hal/intrin_sse.hpp:1438:1: note: candidate function template not viable: requires single argument 'a', but 2 arguments were provided
OPENCV_HAL_IMPL_SSE_SHIFT_OP(v_uint32x4, v_int32x4, epi32, _mm_srai_epi32)
^
/Users/Github/opencv-4.8.0/modules/core/include/opencv2/core/hal/intrin_sse.hpp:1427:16: note: expanded from macro 'OPENCV_HAL_IMPL_SSE_SHIFT_OP'
inline _Tpuvec v_shr(const _Tpuvec& a) \^
/Users/Github/opencv-4.8.0/modules/core/include/opencv2/core/hal/intrin_sse.hpp:1438:1: note: candidate function template not viable: requires single argument 'a', but 2 arguments were provided
/Users/Github/opencv-4.8.0/modules/core/include/opencv2/core/hal/intrin_sse.hpp:1432:16: note: expanded from macro 'OPENCV_HAL_IMPL_SSE_SHIFT_OP'
inline _Tpsvec v_shr(const _Tpsvec& a) \^
/Users/Github/opencv-4.8.0/modules/core/include/opencv2/core/hal/intrin_sse.hpp:1439:1: note: candidate function template not viable: requires single argument 'a', but 2 arguments were provided
OPENCV_HAL_IMPL_SSE_SHIFT_OP(v_uint64x2, v_int64x2, epi64, v_srai_epi64)
^
/Users/Github/opencv-4.8.0/modules/core/include/opencv2/core/hal/intrin_sse.hpp:1427:16: note: expanded from macro 'OPENCV_HAL_IMPL_SSE_SHIFT_OP'
inline _Tpuvec v_shr(const _Tpuvec& a) \^
/Users/Github/opencv-4.8.0/modules/core/include/opencv2/core/hal/intrin_sse.hpp:1439:1: note: candidate function template not viable: requires single argument 'a', but 2 arguments were provided
/Users/Github/opencv-4.8.0/modules/core/include/opencv2/core/hal/intrin_sse.hpp:1432:16: note: expanded from macro 'OPENCV_HAL_IMPL_SSE_SHIFT_OP'
inline _Tpsvec v_shr(const _Tpsvec& a) \^
/Users/Github/opencv_contrib-4.x/modules/xphoto/src/grayworld_white_balance.cpp:328:21: error: no matching function for call to 'v_shr'v_sB1 = v_shr(v_mul(v_sB1, v_gainB), 16);

        编译脚本如下（make -j8，使用并发编译，编译速度会快些）：

make build
cd build
cmake ../ -DCMAKE_INSTALL_PREFIX=/Users/opencv-4.8.0 -DBUILD_SHARED_LIBS=OFF -DOPENCV_EXTRA_MODULES_PATH=/Users/Github/opencv_contrib-4.8.0/modules
make -j8
make install

2 使用

        编写cmake时，强烈建议使用find_package引用头文件和lib库，尤其是lib库，千万不要手动逐个引入lib库。opencv的lib库引用关系表复杂，手动引用会出现各种符号未定义。大量的符号未定义会让人忙到怀疑人生。

        完整的cmake如下所示：

#
#cmake for first_opencv
#
cmake_minimum_required(VERSION 3.28)
set(target "first_opencv")
project(${target})
set(CMAKE_CXX_STANDARD 17)
set(project_path "${CMAKE_CURRENT_SOURCE_DIR}")
file(GLOB srcs "${project_path}/src/*.cpp" "${project_path}/src/*.c")
file(GLOB incs "${project_path}/src/*.hpp" "${project_path}/src/*.h")
source_group(source ${srcs})
source_group(include ${incs})find_package(Iconv)
set(OpenCV_DIR "/Users/libs/opencv-4.8.0/lib/cmake/opencv4")
find_package(OpenCV REQUIRED)
include_directories(${incs} ${OpenCV_INCLUDE_DIRS})add_executable(${target} ${srcs} ${incs})target_link_libraries(${target} ${OpenCV_LIBS})

         注意：

• set(OpenCV_DIR "/Users/libs/opencv-4.8.0/lib/cmake/opencv4")中/Users/libs/opencv-4.8.0/lib/cmake/opencv4为OpenCVConfig.cmake所在的目录，如果不设置OpenCV_DIR，会报下面错误：

CMake Error at CMakeLists.txt:16 (find_package):By not providing "FindOpenCV.cmake" in CMAKE_MODULE_PATH this project hasasked CMake to find a package configuration file provided by "OpenCV", butCMake did not find one.Could not find a package configuration file provided by "OpenCV" with anyof the following names:OpenCVConfig.cmakeopencv-config.cmakeAdd the installation prefix of "OpenCV" to CMAKE_PREFIX_PATH or set"OpenCV_DIR" to a directory containing one of the above files.  If "OpenCV"provides a separate development package or SDK, be sure it has beeninstalled.

• find_package(Iconv)必须添加，否则会报下面的错误：

CMake Error at /Users/libs/opencv-4.8.0/lib/cmake/opencv4/OpenCVModules.cmake:371 (set_target_properties):The link interface of target "opencv_wechat_qrcode" contains:Iconv::Iconvbut the target was not found.  Possible reasons include:* There is a typo in the target name.* A find_package call is missing for an IMPORTED target.* An ALIAS target is missing.Call Stack (most recent call first):/Users/libs/opencv-4.8.0/lib/cmake/opencv4/OpenCVConfig.cmake:133 (include)CMakeLists.txt:16 (find_package)