一次搞定！如何用VSCode编写OpenCV

首先，需要安装MinGW编译器，支持编译C++代码。

安装MinGW编译器

1. 下载MinGW，下载链接为：
   https://nchc.dl.sourceforge.net/project/mingw-w64/Toolchains%20targetting%20Win64/Personal%20Builds/mingw-builds/8.1.0/threads-posix/sjlj/x86_64-8.1.0-release-posix-sjlj-rt_v6-rev0.7z

2. 将MinGW解压缩在某个文件夹中。例如：C:\software\mingw64
   

3. 配置环境变量。

   3.1 右键桌面此电脑，选择属性。
   
   3.2 选择高级系统设置。
   
   3.3 打开环境变量。
   
   3.4 设置path，添加一条路径，为刚刚mingw的下bin文件夹的路径。C:\software\mingw64\bin。
   
   

4. 测试环境变量。win+r打开运行界面，输入cmd进入命令行，输入gcc -v，敲回车，查看gcc是否正常工作。
   

配置Vscode环境，支持编译C++

不用怎么配置，新建一个.cpp文件，用vscode打开，右下角提示是否安装推荐的C++扩展，安装之后就可以编译cpp文件了。
安装完成后，发现新增了如下的VSCode扩展。

下载opencv3

进入官网，https://opencv.org/releases/，下载opencv3，选择Windows进行下载。
安装到指定目录下即可。

下载Cmake

下载路径是：https://cmake.org/download/

将其解压到自定义目录下，我的路径为：C:\software\cmake\bin

点开cmake-gui.exe。
where is source code，选择C:\software\opencv3\opencv\sources
where is to build the binaries，是自己设置的文件夹，选择C:\software\opencv3\opencv\build\x64\mingw。

点击左下角的Configure，选择MinGW Makefiles，Specify native compiler。

Compiler，选择Mingw文件夹bin下的gcc.exe和g++.exe。路径是C:\software\mingw64\bin。

显示configure done。

一定注意这一步，如果不执行这一步，后面依赖的world等dll会缺失。

在执行完后，把关于python的都给取消勾选。勾选BUILD_opencv_world，WITH_OPENGL和BUILD_EXAMPLES，不勾选WITH_IPP、WITH_MSMF和ENABLE_PRECOMPILED_HEADERS（如果有的话），CPU_DISPATCH选空。

这里有一个巨大的坑等着我去踩，解决下面的问题耗费了我两天的时间。如果有后面的人发现自己的opencv C++程序无法正常读取.mp4等视频文件，显示mp4视频文件为零帧、VideoCapture 的isOpened显示为false，是因为在camke的时候没有成功安装ffmpeg。

也就是，执行完configure之后，显示

  Video I/O:
    DC1394:                      NO
    FFMPEG:                      NO
      avcodec:                   NO
      avformat:                  NO
      avutil:                    NO
      swscale:                   NO
      avresample:                NO
    GStreamer:                   NO
    DirectShow:                  YES

此时，按照下面的步骤进行。

1. Ctrl+A，复制指示区的显示内容。
   
2. 复制到一个笔记本里面，搜索其中的failed关键词，找到关于ffmpeg的下载失败内容。内容显示，opencv_ffmpeg.dll, opencv_ffmpeg_64.dll, ffmpeg_version.cmake三个文件下载失败，无法正常运行。

FFMPEG: Download: opencv_ffmpeg.dll
Try 1 failed

=======================================================================
  Couldn't download files from the Internet.
  Please check the Internet access on this host.
=======================================================================

CMake Warning at cmake/OpenCVDownload.cmake:202 (message):
  FFMPEG: Download failed: 6;"Couldn't resolve host name"

  For details please refer to the download log file:

  C:/software/opencv3/opencv/build/x64/mingw/CMakeDownloadLog.txt

Call Stack (most recent call first):
  3rdparty/ffmpeg/ffmpeg.cmake:20 (ocv_download)
  cmake/OpenCVFindLibsVideo.cmake:227 (download_win_ffmpeg)
  CMakeLists.txt:701 (include)


FFMPEG: Download: opencv_ffmpeg_64.dll
Try 1 failed

=======================================================================
  Couldn't download files from the Internet.
  Please check the Internet access on this host.
=======================================================================

CMake Warning at cmake/OpenCVDownload.cmake:202 (message):
  FFMPEG: Download failed: 6;"Couldn't resolve host name"

  For details please refer to the download log file:

  C:/software/opencv3/opencv/build/x64/mingw/CMakeDownloadLog.txt

Call Stack (most recent call first):
  3rdparty/ffmpeg/ffmpeg.cmake:20 (ocv_download)
  cmake/OpenCVFindLibsVideo.cmake:227 (download_win_ffmpeg)
  CMakeLists.txt:701 (include)


FFMPEG: Download: ffmpeg_version.cmake
Try 1 failed

=======================================================================
  Couldn't download files from the Internet.
  Please check the Internet access on this host.
=======================================================================

CMake Warning at cmake/OpenCVDownload.cmake:202 (message):
  FFMPEG: Download failed: 6;"Couldn't resolve host name"

  For details please refer to the download log file:

  C:/software/opencv3/opencv/build/x64/mingw/CMakeDownloadLog.txt

Call Stack (most recent call first):
  3rdparty/ffmpeg/ffmpeg.cmake:20 (ocv_download)
  cmake/OpenCVFindLibsVideo.cmake:227 (download_win_ffmpeg)
  CMakeLists.txt:701 (include)

3. 按照上面的提示报错路径，打开C:/software/opencv3/opencv/build/x64/mingw/CMakeDownloadLog.txt，该文件包含了下载错误的提示信息。

#use_cache "C:/software/opencv3/opencv/sources/.cache"
#do_copy "opencv_ffmpeg.dll" "55c25bbc13e4a12d4339b70d3b76987f" "https://raw.githubusercontent.com/opencv/opencv_3rdparty/0bf6c0753d435d2c82c03c48db0c6e18ac79976c/ffmpeg/opencv_ffmpeg.dll" "C:/software/opencv3/opencv/build/x64/mingw/3rdparty/ffmpeg"
#missing "C:/software/opencv3/opencv/build/x64/mingw/3rdparty/ffmpeg/opencv_ffmpeg.dll"
#cmake_download "C:/software/opencv3/opencv/sources/.cache/ffmpeg/55c25bbc13e4a12d4339b70d3b76987f-opencv_ffmpeg.dll" "https://raw.githubusercontent.com/opencv/opencv_3rdparty/0bf6c0753d435d2c82c03c48db0c6e18ac79976c/ffmpeg/opencv_ffmpeg.dll"
#try 1
# timeout on name lookup is not supported
# getaddrinfo(3) failed for raw.githubusercontent.com:443
# Could not resolve host: raw.githubusercontent.com
# Closing connection 0
# 

#do_copy "opencv_ffmpeg_64.dll" "67caee9231c6843483b4de9815d6526e" "https://raw.githubusercontent.com/opencv/opencv_3rdparty/0bf6c0753d435d2c82c03c48db0c6e18ac79976c/ffmpeg/opencv_ffmpeg_64.dll" "C:/software/opencv3/opencv/build/x64/mingw/3rdparty/ffmpeg"
#missing "C:/software/opencv3/opencv/build/x64/mingw/3rdparty/ffmpeg/opencv_ffmpeg_64.dll"
#cmake_download "C:/software/opencv3/opencv/sources/.cache/ffmpeg/67caee9231c6843483b4de9815d6526e-opencv_ffmpeg_64.dll" "https://raw.githubusercontent.com/opencv/opencv_3rdparty/0bf6c0753d435d2c82c03c48db0c6e18ac79976c/ffmpeg/opencv_ffmpeg_64.dll"
#try 1
# timeout on name lookup is not supported
# getaddrinfo(3) failed for raw.githubusercontent.com:443
# Could not resolve host: raw.githubusercontent.com
# Closing connection 0
# 

#do_copy "ffmpeg_version.cmake" "3b90f67f4b429e77d3da36698cef700c" "https://raw.githubusercontent.com/opencv/opencv_3rdparty/0bf6c0753d435d2c82c03c48db0c6e18ac79976c/ffmpeg/ffmpeg_version.cmake" "C:/software/opencv3/opencv/build/x64/mingw/3rdparty/ffmpeg"
#missing "C:/software/opencv3/opencv/build/x64/mingw/3rdparty/ffmpeg/ffmpeg_version.cmake"
#cmake_download "C:/software/opencv3/opencv/sources/.cache/ffmpeg/3b90f67f4b429e77d3da36698cef700c-ffmpeg_version.cmake" "https://raw.githubusercontent.com/opencv/opencv_3rdparty/0bf6c0753d435d2c82c03c48db0c6e18ac79976c/ffmpeg/ffmpeg_version.cmake"
#try 1
# timeout on name lookup is not supported
# getaddrinfo(3) failed for raw.githubusercontent.com:443
# Could not resolve host: raw.githubusercontent.com
# Closing connection 0
# 

该文件内容很长，但是不要慌，最终的目的是手动下载三个没能下载成功的文件，将它们放到.cache文件夹中。

4. 按照CMakeDownloadLog.txt该文件夹中的内容，我们打开C:/software/opencv3/opencv/sources/.cache文件夹，下面有ffmpeg文件夹，继续打开，发现里面放着三个下载失败的0KB文件。
   
5. 按照CMakeDownloadLog.txt文件中的提示，我们要下载三个对应的文件，分别复制到该文件夹下，并且要求修改文件名和.cache/ffmpeg文件夹下的名称相同。
   .dll文件的下载链接，就是CMakeDownloadLog.txt文件中的对应链接。

"https://raw.githubusercontent.com/opencv/opencv_3rdparty/0bf6c0753d435d2c82c03c48db0c6e18ac79976c/ffmpeg/opencv_ffmpeg.dll" 

"https://raw.githubusercontent.com/opencv/opencv_3rdparty/0bf6c0753d435d2c82c03c48db0c6e18ac79976c/ffmpeg/opencv_ffmpeg_64.dll"

"https://raw.githubusercontent.com/opencv/opencv_3rdparty/0bf6c0753d435d2c82c03c48db0c6e18ac79976c/ffmpeg/ffmpeg_version.cmake" 

修改后的前缀名要保证是与自己的Log文件夹中对应的字符串，这串字符是.md5加密串，后续编译过程，编译器会检查该串与文件的.md5是否相同。

 "55c25bbc13e4a12d4339b70d3b76987f" 

"67caee9231c6843483b4de9815d6526e" 

"3b90f67f4b429e77d3da36698cef700c" 

特别注意的是，.cmake文件从浏览器打开之后，是一个类似文本文档被浏览器打开的内容。

但是，不要将该段文字复制、粘贴到.cache文件夹下的.cmake文件中，因为该下载失败的文件的md5与目标md5是不同的，后续检查会报错。正确做法是Ctrl+S，保存该页面，文件名存为3b90f67f4b429e77d3da36698cef700c-ffmpeg_version.cmake。

6. 将上述三个文件，放到.cache文件夹中，如下。

至此，就把ffmpeg的隐患解决了。

第二次点击Configure。

再点击Generate，最后Generate Done，就完成了。

  Video I/O:
    DC1394:                      NO
    FFMPEG:                      YES (prebuilt binaries)
      avcodec:                   YES (ver 57.107.100)
      avformat:                  YES (ver 57.83.100)
      avutil:                    YES (ver 55.78.100)
      swscale:                   YES (ver 4.8.100)
      avresample:                YES (ver 3.7.0)
    GStreamer:                   NO
    DirectShow:                  YES

make

cmd进入刚刚设置的文件夹C:\software\opencv3\opencv\build\x64\mingw，执行命令: minGW32-make -j 4。

make成功

继续执行minGW32-make install

配置OpenCV的环境变量。

配置Vscode环境，支持OpenCV3

任意创建一个文件夹，放置自己的代码。
最后的文件结构如下：

自己创建.vscode文件夹，自己创建c_cpp_properties.json、launch.json、tasks.json文件。自己创建Debugger文件夹。

c_cpp_properties.json

{
    "configurations": [
        {
            "name": "win",
            "includePath": [
                "${workspaceFolder}/**",
                "C:/software/opencv3/opencv/build/x64/mingw/include",
                "C:/software/opencv3/opencv/build/x64/mingw/install/include/opencv2",
                "C:/software/opencv3/opencv/build/x64/mingw/install/include"
            ],
            "defines": [],
            "compilerPath": "C:/software/mingw64/bin/g++.exe",
            "cStandard": "c11",
            "cppStandard": "c++17",
            "intelliSenseMode": "${default}"
        }
    ],
    "version": 4
}

launch.json

{

    "version": "0.2.0",
    "configurations": [
        {
            "name": "opencv debuge",
            "type": "cppdbg",
            "request": "launch",
            "program": "${workspaceFolder}//Debugger//${fileBasenameNoExtension}.exe",
            //上面这个Debugger是我自己定义的，为了方便放置生成的exe文件
            "args": [],
            "stopAtEntry": false, //这里如果为 false，则说明调试直接运行。（反之则停止）
            "cwd": "${workspaceFolder}",
            "environment": [],
            "externalConsole": true,//是否调用外部cmd
            "MIMode": "gdb",
            "miDebuggerPath": "C:/software/mingw64/bin/gdb.exe",//自己进行设置
            "setupCommands": [
                {
                    "description": "为 gdb 启用整齐打印",
                    "text": "-enable-pretty-printing",
                    "ignoreFailures": false
                }
            ],
            "preLaunchTask": "opencv3.5.2"
        }
    ]
}

tasks.json

{
    "version": "2.0.0",
    "tasks": [
        {
            "type": "shell",
            "label": "opencv3.5.2",
            "command": "C:/software/mingw64/bin/g++.exe",
            "args": [
                "-g",
                "${file}",
                "-o",
                "${workspaceFolder}//Debugger//${fileBasenameNoExtension}.exe",
                //上面这个Debugger是我自己定义的，为了方便放置生成的exe文件
                "C:/software/opencv3/opencv/build/x64/mingw/bin/libopencv_world3416.dll",
                "-I",
                "C:/software/opencv3/opencv/build/x64/mingw/install/include",
                "-I",
                "C:/software/opencv3/opencv/build/x64/mingw/install/include/opencv2",
            ],
            "options": {
                "cwd": "C:/software/mingw64/bin"
            },
            "problemMatcher": [
                "$gcc"
            ],
            "group": {
                "kind": "build",
                "isDefault": true
            }
        }
    ]
}

在C:\software\opencv3\opencv\build\x64\mingw\bin下找到libopencv_world3416.dll，和opencv_ffmpeg3416_64.dll复制到Debugger文件夹下。注意这个后缀3416是OpenCV的版本号，与自己安装的版本有关系。

生成test.cpp文件，输入测试代码。

#include 
#include 
#include 
using namespace cv;
int main()
{
    Mat img=imread("man.jpg");
    imshow("image",img);
    waitKey();
    return 0;
}

能正常运行，就表示图片可以正常运行了。

#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include 
using namespace std;

int main(int argc, char** argv){
    cv::namedWindow("Example3", cv::WINDOW_AUTOSIZE);
    cv::VideoCapture cap;
    cap.open("test.mp4");
    cout<<cap.isOpened()<<endl;
    cv::Mat img; 
    cap >> img;
    std::cout << "image read: " << (img.empty()==true) << std::endl;
    cv::Mat frame;
    for(;;){
        cap >> frame;
        if(frame.empty()) break; // Ran out of film
        cv::imshow("Example3", frame);
        if(cv::waitKey(10) >= 0) break;
    }
    return 0;
}

视频可以正常读取，就表示视频也OK了！
wow！至此，一切成功！