opencv - 带有opencv addexternal的cmake c++库

Question

我想使用cmake构建一个C++库。
该库需要即时下载 opencv并生成，然后该库将在另一个cmake项目中用作库。
项目结构如下:

template_matching_project
    |
    |-- build
    |-- template_matching_project
    |              |
    |              |-- template_matching_library
    |                              |
    |                              | -- src
    |                              | -- include
    |                              | -- CMakeLists.txt
    |-- main.cpp
    |-- CMakeLists.txt

template_matching_library使用opencv执行一些图像处理，template_matching_project / template_matching_library / CMakeLists.txt中包含其cmake文件的内容:

cmake_minimum_required(VERSION 3.0)
set(CMAKE_CXX_STANDARD 11)
project(template_matching)

# third party
include(ExternalProject)
set(EXTERNAL_INSTALL_LOCATION ${CMAKE_BINARY_DIR}/3rdparty)
set(EXTERNAL_DOWNLOAD_LOCATION ${CMAKE_BINARY_DIR}/Download)

# OpenCV
ExternalProject_Add(opencv-contrib
  GIT_REPOSITORY https://github.com/opencv/opencv_contrib.git
  GIT_TAG e6f32c6
  SOURCE_DIR "${EXTERNAL_DOWNLOAD_LOCATION}/opencv-contrib"
  CONFIGURE_COMMAND ""
  BUILD_COMMAND ""
  INSTALL_COMMAND ""
)

ExternalProject_Add(opencv
  GIT_REPOSITORY https://github.com/opencv/opencv.git
  GIT_TAG 01b2c5a
  SOURCE_DIR "${EXTERNAL_DOWNLOAD_LOCATION}/opencv"
  CMAKE_ARGS
    -DBUILD_DOCS:BOOL=OFF
     ...
)
add_dependencies(opencv opencv-contrib)

# set source directories
set(PROJECT_SOURCE_DIR source)
set(INCLUDE_DIR include)

# set source files
file(GLOB_RECURSE SRCS ${PROJECT_SOURCE_DIR}/*)
file(GLOB_RECURSE HEADERS ${INCLUDE_DIR}/*)

# build library
link_directories(${EXTERNAL_INSTALL_LOCATION}/opencv/lib)

include_directories(${EXTERNAL_INSTALL_LOCATION}/opencv/include/opencv4)
include_directories(${INCLUDE_DIR})

add_library(${PROJECT_NAME} SHARED ${SRCS} ${HEADERS})
add_dependencies(${PROJECT_NAME} opencv)

target_link_libraries(${PROJECT_NAME} opencv_core opencv_highgui opencv_imgproc)

target_include_directories(${PROJECT_NAME} PUBLIC ${INCLUDE_DIR})

使用此cmake可以正确构建template_matching_library，但是 main.cpp可执行文件的构建失败
这是template_matching_project / CMakeLists.txt:

cmake_minimum_required(VERSION 3.0)

set(CMAKE_CXX_STANDARD 11)

project(markers)

# include library
add_subdirectory(template_matching_library)
set(EXTERNAL_INSTALL_LOCATION ${CMAKE_BINARY_DIR}/3rdparty)
include_directories(${EXTERNAL_INSTALL_LOCATION}/opencv/include/opencv4)

# add file to compile
set(SRCS main.cpp)

# add executable
add_executable(${PROJECT_NAME} ${SRCS})

# add dependencies
target_link_libraries(${PROJECT_NAME} template_matching)

然后尝试对流构建

cd build
cmake .. -G "Unix Makefiles" -DCMAKE_BUILD_TYPE=Debug
make

我有以下错误

[ 95%] Building CXX object CMakeFiles/markers.dir/main.cpp.o
[100%] Linking CXX executable markers
/usr/bin/ld: cannot find -lopencv_core
/usr/bin/ld: cannot find -lopencv_highgui
/usr/bin/ld: cannot find -lopencv_imgproc
collect2: error: ld returned 1 exit status

有什么建议可以解决我的问题吗？我应该更改那些CMakeLists.txt中的一个还是两个。
谢谢。

Answer 1

如果有人有任何建议或更好的解决方案，我已经将其与这两个CMakeLists.txt一起使用。
template_matching_project / CMakeLists.txt:

cmake_minimum_required(VERSION 3.0)
set(CMAKE_CXX_STANDARD 11)
project(markers)

add_subdirectory(template_matching_library)
set(SRCS main.cpp)
add_executable(${PROJECT_NAME} ${SRCS})
target_link_libraries(${PROJECT_NAME} template_matching ${OpenCV_LIBS})

template_matching_project / template_matching_library / CMakeLists.txt:

cmake_minimum_required(VERSION 3.0)
set(CMAKE_CXX_STANDARD 11)
project(template_matching)

# third party
include(ExternalProject)
set(EXTERNAL_INSTALL_LOCATION ${CMAKE_BINARY_DIR}/3rdparty)
set(EXTERNAL_DOWNLOAD_LOCATION ${CMAKE_BINARY_DIR}/Download)

# OpenCV
ExternalProject_Add(opencv-contrib
  GIT_REPOSITORY https://github.com/opencv/opencv_contrib.git
  GIT_TAG e6f32c6
  SOURCE_DIR "${EXTERNAL_DOWNLOAD_LOCATION}/opencv-contrib"
  ...
)

ExternalProject_Add(opencv
  GIT_REPOSITORY https://github.com/opencv/opencv.git
  GIT_TAG 01b2c5a
  SOURCE_DIR "${EXTERNAL_DOWNLOAD_LOCATION}/opencv"
  CMAKE_ARGS
    -DBUILD_DOCS:BOOL=OFF
    ...
    -DOPENCV_EXTRA_MODULES_PATH:PATH=${EXTERNAL_DOWNLOAD_LOCATION}/opencv-contrib/modules
)
add_dependencies(opencv opencv-contrib)
set(OpenCV_DIR ${EXTERNAL_INSTALL_LOCATION}/opencv/lib/cmake/opencv4)
find_package(OpenCV REQUIRED PATHS ${EXTERNAL_INSTALL_LOCATION}/opencv)

# set source directories
set(PROJECT_SOURCE_DIR source)
set(INCLUDE_DIR include)

# set source files
file(GLOB_RECURSE SRCS ${PROJECT_SOURCE_DIR}/*)
file(GLOB_RECURSE HEADERS ${INCLUDE_DIR}/*)

# build library
include_directories(${EXTERNAL_INSTALL_LOCATION}/opencv/include/opencv4)
include_directories(${INCLUDE_DIR})

add_library(${PROJECT_NAME} SHARED ${SRCS} ${HEADERS})
add_dependencies(${PROJECT_NAME} opencv)

target_link_libraries(${PROJECT_NAME} ${OpenCV_LIBS})

target_include_directories(${PROJECT_NAME} PUBLIC ${INCLUDE_DIR})

不过，除非使用opencv出现链接错误，否则我确实必须使用两次CMakeLists.txt运行两次cmake并执行命令，如下所示:

cd build
cmake .. -G "Unix Makefiles
make 
cmake .. -G "Unix Makefiles
make

有没有办法进行一次单次cmake / make处理？
我尝试了一些 FetchContent，但无法使其正常工作。我的cmake版本是3.5.1