包含带有 fetchcontent 的 opencv 不起作用答案

【问题标题】：Including opencv with fetchcontent does not work包含带有 fetchcontent 的 opencv 不起作用
【发布时间】：2020-10-01 13:50:22
【问题描述】：

我正在尝试在我的 c++ 项目中包含 opencv。我希望 CMake 为我处理这个问题。

目前我需要在标签中包含 opencv：#include <opencv2/opencv.hpp>

_deps/opencv-src 目录中的文件虽然会抛出以下错误：

Scanning dependencies of target VisionC
Building CXX object CMakeFiles/VisionC.dir/main.cpp.o
In file included from /Users/koen/Vakken/MotionVision/VisionC/main.cpp:2:
/Users/koen/Vakken/MotionVision/VisionC/cmake-build-debug/_deps/opencv-src/include/opencv2/opencv.hpp:48:10: fatal error: 'opencv2/opencv_modules.hpp' file not found
#include "opencv2/opencv_modules.hpp"
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.

似乎文件不能包含自己的标题

我的 CMakeLists 文件仍然很简单：

cmake_minimum_required(VERSION 3.17)
project(VisionC)

set(CMAKE_CXX_STANDARD 20)

include(FetchContent)

FetchContent_Declare(
        opencv
        GIT_REPOSITORY https://github.com/opencv/opencv.git
        GIT_TAG        4.4.0
)

FetchContent_GetProperties(opencv)
if (NOT opencv_POPULATED)
    FetchContent_Populate(opencv)
    add_subdirectory(${opencv_SOURCE_DIR} ${opencv_BINARY_DIR})
    include_directories(${opencv_SOURCE_DIR}/include) # "/include" should be deleted somehow...
endif ()

FetchContent_MakeAvailable(opencv)

add_executable(VisionC main.cpp)

target_link_libraries(VisionC opencv_lib)

我认为 include_directories 行中的“/include”暗示该库包含在“高”目录中……我不知道应该如何更改它。如果我删除这一行，我必须包含 opencv，如 #include <include/opencv2/opencv.hpp>

【问题讨论】：

标签： c++ opencv cmake

【解决方案1】：

我找到了解决方案，这是我现在的 cmakelists：

cmake_minimum_required(VERSION 3.17)
project(VisionC)

set(CMAKE_CXX_STANDARD 20)

# Fetch from git
include(FetchContent)

FetchContent_Declare(
        opencv
        GIT_REPOSITORY https://github.com/opencv/opencv.git
        GIT_TAG        4.4.0
)
FetchContent_GetProperties(opencv)
if (NOT opencv_POPULATED)
    FetchContent_Populate(opencv)
endif ()
FetchContent_MakeAvailable(opencv)

# Find on pc
set(OpenCV_DIR ${CMAKE_CURRENT_BINARY_DIR})
include_directories(${OpenCV_INCLUDE_DIRS})
find_package(OpenCV REQUIRED)

# Link
add_executable(VisionC main.cpp)
target_link_libraries(VisionC ${OpenCV_LIBS})

【讨论】：

由于FetchContent_MakeAvailable(opencv)遵循规范模式，您可以删除FetchContent_GetProperties/FetchContent_Populate，即一切都由FetchContent_MakeAvailable完成...参考：cmake.org/cmake/help/latest/module/…
你说得对，我也觉得include_directories(${OpenCV_INCLUDE_DIRS})
我尝试和你做同样的事情，但我有如下错误列表：Target "opencv_core" INTERFACE_INCLUDE_DIRECTORIES property contains path: "~/CLionProjects/vision/cmake-build-debug" which is prefixed in the build directory.你知道为什么吗？
老实说，这是一个学校项目。我只是带着它跑。对不起。也许您可以简单地更改 INTERFACE_INCLUDE_DIRECTORIES 的值以排除该路径并查看会发生什么。老实说，如果你能解决这个问题，我想很多人将来会很开心！