native_opencv

• 开发flutter 桌面版本

  • 创建项目

    • flutter config --enable-macos-desktop
    • flutter config --enable-windows-desktop
    • flutter config --enable-linux-desktop
    • flutter devices
    • flutter create desktopapp // 创建项目

• dart::ffi 实现具有原生 OpenCV 支持的 Flutter 插件

  • 需要安装homebrew 、 python2、cmake(3.21 或更新版本)
  • 下载继承opencv
    • 参考文档 [Integrating C library in a Flutter app using Dart FFI] 和 [Integrating C library in a desktop Flutter app using Dart FFI]
    • ios：
      • https://opencv.org/releases 下点击平台下载
      • 将下载下来的opencv2.framework放到插件的ios下，同级native_opencv.podspec下写上：

      • 			    # 告诉 CocoaPods 不要删除框架
        			    s.preserve_paths = 'opencv2.framework'
        			    # 告诉链接器包含 opencv2 框架
        			    s.xcconfig = { 'OTHER_LDFLAGS' => '-framework opencv2' }
        			    # 包括 OpenCV 框架
        			    s.vendored_frameworks = 'opencv2.framework'
        			    # 包括原生框架
        			    s.frameworks = 'AVFoundation'
        			    # 包括 C++ 库
        			    s.library = 'c++'
        

      • 执行pod install刷新
    • macos：
      • git clone https://github.com/opencv/opencv
      • python3 ~/dev/lib/opencv/platforms/apple/build_xcframework.py --macos_archs=x86_64,arm64 --build_only_specified_archs --out ./build_xcframework
      • 生成如下：
      • 
      • 将opencv2.xcframework放到macos文件夹下，同级native_opencv.podspec下写上：

      • 			  #   告诉 CocoaPods 不要删除框架
        			     s.preserve_paths = 'opencv2.xcframework'
        			  #   告诉链接器包含 opencv2 框架
        			     s.xcconfig = { 'OTHER_LDFLAGS' => '-framework opencv2' }
        			  #   包括 OpenCV 框架
        			     s.vendored_frameworks = 'opencv2.xcframework'
        			    # 包括原生框架
        			    s.frameworks = 'AVFoundation', 'Accelerate', 'OpenCL'
        			    # 包括 C++ 库
        			    s.library = 'c++'
        

      • 在example的macos下执行pod install，刷新podspec依赖

    • Android：

    • Window：
      • https://opencv.org/releases 下点击平台下载，
    • Linux：
      • Linux下的flutter记得用[手动安装方式]，不要使用snap，不然会clang link fail
        • 下载flutter_linux_x.x.x-stable.tar.xz

        • 解压

          ```
          					  tar xf ~/Downloads/flutter_linux_3.3.0-stable.tar.xz
          ```
          

        • 设置flutter环境变量

          ```
          					  echo 'export PATH="$PATH:~/Downloads/flutter/bin"' >> ~/.bashrc
          ```
          

      • 根据网站执行official OpenCV website.

        ```
        				  # Install minimal prerequisites (Ubuntu 18.04 as reference)
        				  sudo apt update && sudo apt install -y cmake g++ wget unzip
        
        				  # Download and unpack sources
        				  wget -O opencv.zip https://github.com/opencv/opencv/archive/4.x.zip
        				  unzip opencv.zip
        
        				  # Create build directory
        				  mkdir -p build && cd build
        
        				  # Configure
        				  cmake  ../opencv-4.x
        
        				  # Build
        				  cmake --build .
        ```
        

      • 将OpenCV_DIR写进环境变量

        • 				  # 将OpenCV_DIR写进环境变量
          				  echo 'export OpenCV_DIR=/home/west/dev/lib/opencv/build' >> ~/.bashrc
          

        • 这里虽然写了，但是后续使用还是报错找不到OpenCVConifg.cmake，所以在插件linux下的cmakelist.text里写的还是

          ```
          					  # set("OpenCV_DIR" $ENV{OpenCV_DIR})
          					  set("OpenCV_DIR" /home/west/dev/lib/opencv/build)
          ```