Wraps a Dart image so that it can be passed as a parameter to synchronous methods while loading asynchronously

async_image.dart

/*
 * Based on: https://gist.github.com/jonathanduke/b3385b350b7fa02019ba9927c5fa3f5a
 * Public domain: http://unlicense.org/
 * Modify as you wish, but you are encouraged to leave this comment for future reference in case the original is updated.
 */

import 'dart:async';
import 'dart:convert';
import 'dart:typed_data';
import 'dart:ui';

class AsyncImage {
  late final Future<Image> future;
  late Image? _image;
  late Uint8List? _bytes;

  AsyncImage._();

  bool get isLoaded => _image != null;
  Image get image => _image!;
  bool get hasBytes => _bytes != null;
  Uint8List get bytes => _bytes!;

  static Future<Image> _loadImageFromBytes(Uint8List bytes) async {
    final completer = Completer<Image>();
    runZonedGuarded(() {
      decodeImageFromList(bytes, (img) {
        completer.complete(img);
      });
    }, (ex, st) {
      completer.completeError(ex, st);
    });
    return await completer.future;
  }

  static Future<Uint8List> _getBytesFromImage(Image image) async => await image
      .toByteData(format: ImageByteFormat.rawUnmodified)
      .then((data) => data!.buffer.asUint8List());

  factory AsyncImage.fromImage(Image image) {
    final instance = AsyncImage._().._image = image;
    instance.future = Future.value(image).then((image) async {
      instance._bytes = await _getBytesFromImage(image);
      return image;
    });
    return instance;
  }

  factory AsyncImage.fromUint8List(Uint8List bytes) {
    final instance = AsyncImage._().._bytes = bytes;
    instance.future = _loadImageFromBytes(bytes).then((image) {
      instance._image = image;
      return image;
    });
    return instance;
  }

  static AsyncImage fromByteData(ByteData byteData) =>
      AsyncImage.fromUint8List(byteData.buffer.asUint8List());

  static AsyncImage fromBase64(String source) =>
      AsyncImage.fromUint8List(base64Decode(source));

  String toBase64() => base64Encode(_bytes!);
}