64 lines
2.8 KiB
Markdown
64 lines
2.8 KiB
Markdown
# flutter_native_opencv
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Using OpenCV natively in C++ in a Flutter app with Dart FFI. Tested with Flutter 2.5.2.
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Read the full article here: https://medium.com/flutter-community/integrating-c-library-in-a-flutter-app-using-dart-ffi-38a15e16bc14
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# How to build & run
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## Android and iOS
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Run `init.sh` script from a `scripts` folder or do the following steps manually:
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1. Download OpenCV for Android and iOS: https://opencv.org/releases/
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2. Copy or create symlinks:
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- `opencv2.framework` to `native_opencv/ios`
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- `OpenCV-android-sdk/sdk/native/jni/include` to `native_opencv`
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- Contents of `OpenCV-android-sdk/sdk/native/libs/**` to `native_opencv/android/src/main/jniLibs/**`
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## Windows
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Run `init_windows.ps1` PowerShell script from a `scripts` folder or do the following steps manually:
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1. Download OpenCV for Windows: https://opencv.org/releases/
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2. Unpack it. Set env. variable `OpenCV_DIR` to unpacked `...\opencv\build` folder
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3. Create a hard link from `native_opencv\ios\Classes\native_opencv.cpp` to `native_opencv_windows\windows\native_opencv.cpp`
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4. Make sure `native_opencv_windows\windows\CMakeLists.txt` contains correct .dll names (OpenCV_DEBUG_DLL_NAME,OpenCV_RELEASE_DLL_NAME)
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## macOS
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Before doing anything else, you need to download OpenCV source code and
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build a framework by running `opencv/platforms/apple/build_xcframework.py` script.
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Run `init_macos.sh` script from a `scripts` folder or do the following steps manually:
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1. Create a hard link from `native_opencv/ios/Classes/native_opencv.cpp` to `native_opencv_macos/macos/Classes/native_opencv.cpp`
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2. Copy `opencv2.xcframework` to `native_opencv/macos`
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## Linux
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Before doing anything else, you need to download OpenCV source code and
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build libraries by following [the official tutorial](https://docs.opencv.org/master/d7/d9f/tutorial_linux_install.html).
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After making a build, set up an environmental variable `OpenCV_DIR` to the build's folder.
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Run `init_linux.sh` script from a `scripts` folder or do the following steps manually:
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1. Create a hard link from `native_opencv/ios/Classes/native_opencv.cpp` to `native_opencv_linux/linux/native_opencv.cpp`
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# Troubleshooting
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```
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/snap/flutter/current/usr/include/x86_64-linux-gnu/gnu/stubs.h:7:11: fatal error: 'gnu/stubs-32.h' file not found
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# include <gnu/stubs-32.h>
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^~~~~~~~~~~~~~~~
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1 error generated.
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ninja: build stopped: subcommand failed.
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```
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or
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```
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/snap/flutter/current/usr/bin/ld: warning: /usr/lib/gcc/x86_64-linux-gnu/11/../../../x86_64-linux-gnu/crt1.o: unsupported GNU_PROPERTY_TYPE (5) type: 0xc0008002
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clang: error: linker command failed with exit code 1 (use -v to see invocation)
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Exception: Build process failed
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```
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Install flutter manually instead of from snap, see: https://flutter.dev/docs/get-started/install/linux#install-flutter-manually |