ffi_opencv

Plugin to use OpenCV with dart:ffi

Getting Started

Download OpenCV sources for Android from here, 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.