https://github.com/alnitak/flutter_ffi_opencv

Test OpenCV in Flutter using dart:ffi
https://github.com/alnitak/flutter_ffi_opencv

dart ffi flutter flutter-plugin opencv

Last synced: 27 days ago
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Test OpenCV in Flutter using dart:ffi

• Host: GitHub
• URL: https://github.com/alnitak/flutter_ffi_opencv
• Owner: alnitak
• License: mit
• Created: 2020-06-27T12:18:24.000Z (over 4 years ago)
• Default Branch: master
• Last Pushed: 2020-06-27T12:33:51.000Z (over 4 years ago)
• Last Synced: 2024-10-02T10:21:16.319Z (about 1 month ago)
• Topics: dart, ffi, flutter, flutter-plugin, opencv
• Language: CMake
• Homepage:
• Size: 681 KB
• Stars: 7
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • Changelog: CHANGELOG.md
  • License: LICENSE

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README

        
# ffi_opencv

Plugin to use OpenCV with dart:ffi

## Getting Started

Download OpenCV sources for Android from

[here](https://opencv.org/releases/),

then edit **android/CMakeLists.txt** to point **OPENCV_DIR** variable to the unzipped OpenCV path.

By subclassing ImgProc to add a new image filter, you should averride *compute()* or *computeSync()* or both.

**compute()** is used by *OpenCVImageProvider* asynchronously. That means that the image is read and decompressed every time it is needed by *OpenCVImageProvider*.

**computeSync()** calls the C filter with an already loaded image cv::Mat. Use *preloadUriImage()* or *preloadBytesImage()* to store the iamge before calling *computeSync()*.

By now there are only 2 image proc filters: *blur* and *dilate*.

#

***using OpenCVImageProvider***

```

Image(

      image: OpenCVImageProvider(

        'assets/solar-system.jpg', // only assets images for now

        [ // list of filters

          Dilate(kernelSize: 9),

          Blur(kernelSize: 15),

        ]

  )),

)

```

***using computeSync()***  

define your subclassed ImgProc classes:

```

  Blur _blur;

  Dilate _dilate;

  @override

  void initState() {

    super.initState();

    _blur = Blur();

    _dilate = Dilate();

    _init();

  }  

```

the *_init()* method is used to preload asynchronously the image into the first to process ImgProc class:

```

  _init() async{

    // when using ImgProc.computeSync(), we must use Blur.preloadImage() before

    await _blur.preloadUriImage('assets/solar-system.jpg');

    setState(() {

      canBuild = true;

    });

  }

```

when done, the *build()* can be called.

The preloaded image is processed by *Blur* and the resulting image bytes are then passed to *Dilate* to be processed.

```

Widget _computeFilters() {

    Uint8List bytes = _blur.computeSync().bytes;

    if (bytes != null) {

      // feed dilate with the output of blur

      _dilate.preloadBytesImage(bytes);

      bytes = _dilate.computeSync().bytes;

    }

    if (bytes != null)

      return Image.memory(bytes);

    return Container(child: Text('Image filter error'));

  }

```

#### issues

Sometimes the 2nd *computeSync()* returns wrong image bytes.  

On my Asus Zenfone there is some kind of about freeing pointer.