Image Cropping plugin for Flutter #

A flutter plugin to crop image on iOS and Android.

Note: This plugin is still under development, some billing features are not available yet and testing has been limited.

Installation #

Add image_crop as a dependency in pubspec.yaml.

Using #

Create a widget to load and edit an image:

final cropKey = GlobalKey<CropState>();

Widget _buildCropImage() {
  return Container(
      color: Colors.black,
      padding: const EdgeInsets.all(20.0),
      child: Crop(
        key: cropKey,
        image: Image.file(imageFile),
        aspectRatio: 4.0 / 3.0,
      ),
  );
}

Access cropping values:

• scale is a factor to proportionally scale image's width and height when cropped. 1.0 is no scale needed.
• area is a rectangle indicating fractional positions on the image to crop from.

final crop = cropKey.currentState;
// or
// final crop = Crop.of(context);
final scale = crop.scale;
final area = crop.area;

if (area == null) {
    // cannot crop, widget is not setup
    // ...
}

Accessing and workign with images. As a convenience function to request permissions to access photos.

final permissionsGranted = await ImageCrop.requestPermissions();

Read image options, such as: width and height. This is efficent implementation that does not decode nor load actual image into a memory.

final options = await getImageOptions(file: file);
debugPrint('image width: ${options.width}, height: ${options.height}');

If image is large to be loaded into the memory, there is a sampling function that relies on a native platform to proportionally scale down the image befor loading it to the memory. e.g. resample image to get down to 1024x4096 dimension as close as possible. If it is a square preferredSize can be used to specify both width and height.

final sampleFile = await ImageCrop.sampleImage(
    file: originalFile,
    preferredWidth: 1024,
    preferredHeight: 4096,
);

Once Crop widget is ready, there is a native support of croping and scaling an image.

final croppedFile = await ImageCrop.cropImage(
    file: originalFile,
    scale: crop.scale,
    area: crop.area,
);

All of the computation intensive work is done off a main thread via dispatch queues on iOS and cache thread pool on Android.