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 install2 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 has
asked CMake to find a package configuration file provided by "OpenCV", but
CMake did not find one.
Could not find a package configuration file provided by "OpenCV" with any
of the following names:
OpenCVConfig.cmake
opencv-config.cmake
Add 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 been
installed.- 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::Iconv
but 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)
