Visual Studio 2022新建 cmake 工程测试 opencv helloworld

1. 参考博客：

1.1. https://blog.csdn.net/yangSHU21/article/details/130237669( 利用OpenCV把一幅彩色图像转换成灰度图 )( vs2022_cmake_test.cpp 中的代码用的此博客的，就改了下图片文件路径而已 )

2. 检查 Visual Studio 2022是否支持 cmake：

打开 Visual Studio installer：

已安装--》修改：

工作负荷--》使用C++的桌面开发--》可选--》如果 "用于 windows的 C++ cmake工具" 勾选了，即表示你的 Visual Studio 2022 支持 cmake：

3. 操作步骤：

打开 Visual Studio 2022 --》创建新项目--》搜索 cmake--》选择 "cmake 项目( 生成不依赖于 .sln 或 .vcxproj 文件的新式跨平台 C++ 应用。 )"--》点击下一步--》设置项目名称、位置--》点击创建，默认生成的 vs2022_cmake_test_02.cpp 文件内容如下：

#include "vs2022_cmake_test_02.h"
using namespace std;int main()
{cout << "Hello CMake." << endl;return 0;
}

默认生成的 CMakeLists.txt内容如下：

cmake_minimum_required (VERSION 3.8)# 如果支持，请为 MSVC 编译器启用热重载。
if (POLICY CMP0141)cmake_policy(SET CMP0141 NEW)set(CMAKE_MSVC_DEBUG_INFORMATION_FORMAT "$<IF:$<AND:$<C_COMPILER_ID:MSVC>,$<CXX_COMPILER_ID:MSVC>>,$<$<CONFIG:Debug,RelWithDebInfo>:EditAndContinue>,$<$<CONFIG:Debug,RelWithDebInfo>:ProgramDatabase>>")
endif()project ("vs2022_cmake_test_02")# 将源代码添加到此项目的可执行文件。
add_executable (vs2022_cmake_test_02 "vs2022_cmake_test_02.cpp" "vs2022_cmake_test_02.h")if (CMAKE_VERSION VERSION_GREATER 3.12)set_property(TARGET vs2022_cmake_test_02 PROPERTY CXX_STANDARD 20)
endif()

将 vs2022_cmake_test.cpp 的内容修改为如下所示：

#include "vs2022_cmake_test_02.h"
#include <opencv2\opencv.hpp>using namespace cv;
using namespace std;void opencv_test();
void ConvertRGB2GRAY(const Mat& image, Mat& imageGray);void opencv_test() {Mat src = imread("D:/素材/图片/壁纸/0001.jpg");Mat src0 = imread("D:/素材/图片/壁纸/0001.jpg", 0);Mat grayImage;Mat cvt_gray_image;//读入的彩色图namedWindow("origin_image", WINDOW_NORMAL);imshow("origin_image", src);//opencv使用imread函数读入彩色图，设置第二个参数为0得到的灰度图namedWindow("opencv_image", WINDOW_NORMAL);imshow("opencv_image", src0);//使用公式GRAY=0.299*R+0.587*G+0.114*BConvertRGB2GRAY(src, grayImage);namedWindow("my_gray_image", WINDOW_NORMAL);imshow("my_gray_image", grayImage);//先读入彩色图，然后使用cvtColor函数进行灰度转化cvtColor(src, cvt_gray_image, COLOR_BGR2GRAY);namedWindow("cvt_gray_image", WINDOW_NORMAL);imshow("cvt_gray_image", cvt_gray_image);waitKey(0);
}void ConvertRGB2GRAY(const Mat& image, Mat& imageGray)
{if (!image.data || image.channels() != 3){return;}//创建一张单通道的灰度图像imageGray = Mat::zeros(image.size(), CV_8UC1);//取出存储图像像素的数组的指针uchar* pointImage = image.data;uchar* pointImageGray = imageGray.data;//取出图像每行所占的字节数size_t stepImage = image.step;size_t stepImageGray = imageGray.step;for (int i = 0; i < imageGray.rows; i++){for (int j = 0; j < imageGray.cols; j++){//opencv的通道顺序是BGR，而不是我们常说的RGB顺序pointImageGray[i * stepImageGray + j] =(uchar)(0.114 * pointImage[i * stepImage + 3 * j] +0.587 * pointImage[i * stepImage + 3 * j + 1] +0.299 * pointImage[i * stepImage + 3 * j + 2]);}}
}int main()
{cout << "Hello CMake." << endl;opencv_test();return 0;
}

此时 vs2022 报错 "找不到opencv 的头文件"：

找到 opencv2 的位置如下所示：

可以直接将 "D:\install\opencv\opencv\build\include" 加入进来，即在 CMakeLists.txt 中加入如下指令：

include_directories( "D:/install/opencv/opencv/build/include" )

但是这样不太优雅，优雅的做法是加入如下指令：

 find_package(OpenCV REQUIRED)

其作用是查找 OpenCV 包，找到以后就可以直接使用内置变量 OpenCV_INCLUDE_DIRS 和 OpenCV_LIBS 了( 分别表示 opencv 的头文件的目录位置和链接库的目录位置 )，但是 cmake 是从哪里去找 opencv 呢？可能它内置的有一些策略吧，不放心的话或者电脑装了多个版本的 opencv，其实可以手动指定查找位置，即使用如下指令：

set(OpenCV_DIR "D:/install/opencv/opencv/build")

这里指定 "D:/install/opencv/opencv/build" 的依据是什么呢？到底是 opencv 的根目录还是头文件目录还是链接库目录呢？其实应该写 opencv 编译目录中

OpenCVConfig.cmake

文件所在的目录，例如我电脑中 OpenCVConfig.cmake 所在位置如下所示：

所以我指定的是 D:/install/opencv/opencv/build( ps：windows中 CMakeLists.txt 中的路径最好写正斜线，不能写反斜线！！！不知道双反斜线可不可以？没试过 )

修改后的最终完整的 CMakeLists.txt 如下所示：

cmake_minimum_required (VERSION 3.8)# 如果支持，请为 MSVC 编译器启用热重载。
if (POLICY CMP0141)cmake_policy(SET CMP0141 NEW)set(CMAKE_MSVC_DEBUG_INFORMATION_FORMAT "$<IF:$<AND:$<C_COMPILER_ID:MSVC>,$<CXX_COMPILER_ID:MSVC>>,$<$<CONFIG:Debug,RelWithDebInfo>:EditAndContinue>,$<$<CONFIG:Debug,RelWithDebInfo>:ProgramDatabase>>")
endif()project ("vs2022_cmake_test_02")set(OpenCV_DIR "D:/install/opencv/opencv/build")
# 查找OpenCV包
find_package(OpenCV REQUIRED)# include_directories( "D:/install/opencv/opencv/build/include" )
# set(CMAKE_LIBRARY_PATH "D:/install/opencv/opencv/build/x64/vc16/bin"  "D:/install/opencv/opencv/build/x64/vc16/lib" )# 如果OpenCV被找到，包含其头文件目录和库
message( "--------------------------------------------------" )
message( "--------------------------------------------------" )
message( "--------------------------------------------------" )
message( "OpenCV_INCLUDE_DIRS = ${OpenCV_INCLUDE_DIRS}"  )
message( "OpenCV_LIBS = ${OpenCV_LIBS}" )
message( "OpenCV_FOUND = ${OpenCV_FOUND}" )if(OpenCV_FOUND)message( "OpenCV founded" )include_directories(${OpenCV_INCLUDE_DIRS})
endif()# 将源代码添加到此项目的可执行文件。
add_executable (vs2022_cmake_test_02 "vs2022_cmake_test_02.cpp" "vs2022_cmake_test_02.h")if(OpenCV_FOUND)message( "OpenCV founded" )target_link_libraries(vs2022_cmake_test_02 ${OpenCV_LIBS})
endif()message( "------------------------------------------------" )
message( "-----------------------------------------------" )
message( "--------------------------------------------------" )if (CMAKE_VERSION VERSION_GREATER 3.12)set_property(TARGET vs2022_cmake_test_02 PROPERTY CXX_STANDARD 20)
endif()

这时候编译就成功了，部分输出信息如下：

1> 工作目录: D:/code/c_code/cpp_study_demo/vs2022/vs2022_cmake_test_02/out/build/x64-debug
1> [CMake] -- OpenCV ARCH: x64
1> [CMake] -- OpenCV RUNTIME: vc16
1> [CMake] -- OpenCV STATIC: OFF
1> [CMake] -- Found OpenCV 4.10.0 in D:/install/opencv/opencv/build/x64/vc16/lib
1> [CMake] -- You might need to add D:\install\opencv\opencv\build\x64\vc16\bin to your PATH to be able to run your applications.
1> [CMake] --------------------------------------------------
1> [CMake] --------------------------------------------------
1> [CMake] --------------------------------------------------
1> [CMake] OpenCV_INCLUDE_DIRS = D:/install/opencv/opencv/build/include
1> [CMake] OpenCV_LIBS = opencv_calib3d;opencv_core;opencv_dnn;opencv_features2d;opencv_flann;opencv_gapi;opencv_highgui;opencv_imgcodecs;opencv_imgproc;opencv_ml;opencv_objdetect;opencv_photo;opencv_stitching;opencv_video;opencv_videoio;opencv_world
1> [CMake] OpenCV_FOUND = 1
1> [CMake] OpenCV founded
1> [CMake] OpenCV founded
1> [CMake] ------------------------------------------------
1> [CMake] -----------------------------------------------
1> [CMake] --------------------------------------------------
1> [CMake] -- Configuring done (0.0s)
1> [CMake] -- Generating done (0.0s)
1> [CMake] -- Build files have been written to: D:/code/c_code/cpp_study_demo/vs2022/vs2022_cmake_test_02/out/build/x64-debug
1> 已提取 CMake 变量。
1> 已提取源文件和标头。
1> 已提取代码模型。
1> 已提取工具链配置。
1> 已提取包含路径。
1> CMake 生成完毕。

可以看到：

OpenCV_INCLUDE_DIRS = D:/install/opencv/opencv/build/include
OpenCV_LIBS = opencv_calib3d;opencv_core;opencv_dnn;opencv_features2d;opencv_flann;opencv_gapi;opencv_highgui;opencv_imgcodecs;opencv_imgproc;opencv_ml;opencv_objdetect;opencv_photo;opencv_stitching;opencv_video;opencv_videoio;opencv_world

格式化一下：

OpenCV_INCLUDE_DIRS = D:/install/opencv/opencv/build/include
OpenCV_LIBS = opencv_calib3d;opencv_core;opencv_dnn;opencv_features2d;opencv_flann;opencv_gapi;opencv_highgui;opencv_imgcodecs;opencv_imgproc;opencv_ml;opencv_objdetect;opencv_photo;opencv_stitching;opencv_video;opencv_videoio;opencv_world

这时候运行 vs2022_cmake_test_02.exe报错：

使用 Everything 搜索下 opencv_world4100.dll：

应该把 D:\install\opencv\opencv\build\x64\vc16\bin 加入环境变量，其实刚才 cmake 的输入信息中已经建议这样做了：

1> [CMake] -- Found OpenCV 4.10.0 in D:/install/opencv/opencv/build/x64/vc16/lib
1> [CMake] -- You might need to add D:\install\opencv\opencv\build\x64\vc16\bin to your PATH to be able to run your applications.
1> [CMake] --------------------------------------------------
1> [CMake] --------------------------------------------

加入环境变量：

这时候就运行成功了：

记得打开新的 cmd 测试，如果是在 vs2022中测试也需要关闭工程重新打开进行测试。

4. CMakeLists.txt 中直接使用的变量 OpenCV_INCLUDE_DIRS、OpenCV_LIBS、OpenCV_FOUND 是在哪里定义的？

打开 D:\install\opencv\opencv\build 下面的 OpenCVConfig.cmake，找到如下内容：

#    This file will define the following variables:
#      - OpenCV_LIBS                     : The list of libraries to link against.
#      - OpenCV_INCLUDE_DIRS             : The OpenCV include directories.
#      - OpenCV_COMPUTE_CAPABILITIES     : The version of compute capability
#      - OpenCV_VERSION                  : The version of this OpenCV build: "4.10.0"
#      - OpenCV_VERSION_MAJOR            : Major version part of OpenCV_VERSION: "4"
#      - OpenCV_VERSION_MINOR            : Minor version part of OpenCV_VERSION: "10"
#      - OpenCV_VERSION_PATCH            : Patch version part of OpenCV_VERSION: "0"
#      - OpenCV_VERSION_STATUS           : Development status of this build: ""

说此文件定义了这几个变量，但是这只是注释，此文件并没有直接有声明比如 set( OpenCV_INCLUDE_DIRS ... ) 的地方，可能是该文件引用的其他文件声明了，在该文件中找到了如下内容：


function(check_one_config RES)set(${RES} "" PARENT_SCOPE)if(NOT OpenCV_RUNTIME OR NOT OpenCV_ARCH)return()endif()set(candidates)if(OpenCV_STATIC)list(APPEND candidates "${OpenCV_ARCH}/${OpenCV_RUNTIME}/staticlib")endif()if(OpenCV_CUDA)list(APPEND candidates "gpu/${OpenCV_ARCH}/${OpenCV_RUNTIME}/lib")endif()if(OpenCV_CUDA AND OpenCV_STATIC)list(APPEND candidates "gpu/${OpenCV_ARCH}/${OpenCV_RUNTIME}/staticlib")endif()list(APPEND candidates "${OpenCV_ARCH}/${OpenCV_RUNTIME}/lib")foreach(c ${candidates})set(p "${OpenCV_CONFIG_PATH}/${c}")if(EXISTS "${p}/OpenCVConfig.cmake")set(${RES} "${p}" PARENT_SCOPE)return()endif()endforeach()
endfunction()

定义了一个集合变量 candidates，如下一行：

 list(APPEND candidates "${OpenCV_ARCH}/${OpenCV_RUNTIME}/lib")

应该是往集合 candidates 中追加一个路径类型的元素，其中路径中的 OpenCV_ARCH 应该对应我电脑环境的 x64，OpenCV_RUNTIME 应该对应 vc16，果然在 D:\install\opencv\opencv\build\x64\vc16\lib 下面找到了 OpenCVConfig.cmake：

打开此文件，发现了定了定义变量 OpenCV_INCLUDE_DIRS 的地方：

Visual Studio 2022新建 cmake 工程测试 opencv helloworld

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