![]() ![]() We will not dive into the details of using OpenCV, so you can just use the final code already present in our demo app’s src/umbrella folder. This class processes image frames using OpenCV, then returns all circles found on it. Note: All C++ code should be placed in the directory src/umbrella, as it’s not platform-specific.įirst, we will implement a ShapeDetectorclass. We will then create a dart::ffi native layer that wraps C++ logic. Now that we have successfully built the OpenCV binaries, let's write some C++ code that uses them. The builds of our actual plugin project will run much faster. This will take quite a while, but you only have to do it once. The script prebuild.sh will launch them both: cd src/ 3) Build OpenCVĪfter we have prepared the build scripts for both platforms, we can run them from the terminal. Those scripts will download the OpenCV sources from GitHub and build them. You can find our build scripts for OpenCV in the corresponding platform directories: Therefore, we have put together the following GitHub repository, which contains all the build scripts and other project files for this tutorial: Ĭopy the whole src directory from this repository into your Flutter project directory flutter_ffi_demo. It's not easy to build OpenCV for all architectures. export ANDROID_HOME=/$HOME/Library/Android/sdkĮxport ANDROID_NDK_HOME=$ANDROID_HOME/ndk-bundle Make sure your NDK version is newer than 23.0.75. Typically, you add them to your shell config file, e.g., ~/.bashrc or ~/.zshrc. If you don’t, use the following HomeBrew commands to install and link it: $ brew install cmake $ brew unlink cmake & brew link cmakeįor the Android SDK and NDK, define the following paths as environment variables. Make sure you have CMake version 3.21 or newer installed ( $ cmake -version). Next we need to prepare the OpenCV sources for iOS and Android as well as the build scripts. platforms=android,ios -a kotlin flutter_ffi_demo This will contain a template for a Flutter plugin as well as an example app: $ flutter create -org com.example -template=plugin ![]() ![]() Use the following Flutter command to create the project flutter_ffi_demo. Let's go! Preparations 1) Create a template project for a Flutter plugin Once you’ve set all that up, we can start our project. For Android: latest Android Studio with Android NDK (v23.0.75+) installed.The following tools must be installed on macOS:.Windows or Linux can also be used with corresponding adjustments. We are assuming that you are already familiar with the Flutter framework.Everything else can be only represented as a NativeType type. There is a limited number of data types you can map between dart::ffi and C: pointer, int, float, Uint8, Uint16, and function.The C++ code has to be wrapped with an extern C interface, so we need to write quite a lot of boilerplate code.Using a C++ library requires writing a lot of wrapper code. ![]()
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