Flutter Image Editor

image_editor.dart

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

const _BYTES_PER_PIXEL = 4;

class ImageEditor {
  final int imageWidth;
  final int imageHeight;
  final ByteData _byteData;

  ImageEditor._(
    this.imageWidth,
    this.imageHeight,
    this._byteData,
  );

  ImageEditor(this.imageWidth, this.imageHeight)
      : _byteData = ByteData(imageWidth * imageHeight * _BYTES_PER_PIXEL);

  static Future<ImageEditor?> load(Image image) async {
    final byteData = await image.toByteData();
    if (byteData == null) return null;
    return ImageEditor._(image.width, image.height, byteData);
  }

  Future<Image> render() async {
    final bytes = _byteData.buffer.asUint8List(
      _byteData.offsetInBytes,
      _byteData.lengthInBytes,
    );
    final completer = Completer<Image>();
    decodeImageFromPixels(
      bytes,
      imageWidth,
      imageHeight,
      PixelFormat.rgba8888,
      completer.complete,
    );
    return completer.future;
  }

  Color getColor(int x, int y) {
    final byteOffset = (y * imageWidth + x) * _BYTES_PER_PIXEL;
    final bytes = _byteData.getUint32(byteOffset);
    final r = (bytes & 0xFF << 24) >> 24;
    final g = (bytes & 0xFF << 16) >> 16;
    final b = (bytes & 0xFF << 08) >> 08;
    final a = (bytes & 0xFF << 00) >> 00;
    return Color.fromARGB(a, r, g, b);
  }

  void setColor(Color color, int x, int y) {
    final byteOffset = (y * imageWidth + x) * _BYTES_PER_PIXEL;
    final a = color.alpha;
    final r = color.red;
    final g = color.green;
    final b = color.blue;
    _byteData.setUint8(byteOffset + 0, r);
    _byteData.setUint8(byteOffset + 1, g);
    _byteData.setUint8(byteOffset + 2, b);
    _byteData.setUint8(byteOffset + 3, a);
  }
}