crop image to square in Dart

main.dart

import 'dart:io';
import 'dart:math';
import 'dart:isolate';
import 'package:image/image.dart';
import 'package:http/http.dart' as http;
import 'package:flutter/foundation.dart';
import 'package:safe_local_storage/safe_local_storage.dart';

/// This method crops passed given [image] into square & returns it
/// as [Uint8List] in JPEG format.
/// The passed [image] may be:
/// * [Uri] or [String] - URL to the image.
/// * [File] - local file.
/// * [Uint8List] or [List<int>] - encoded image data.
///
/// The method is asynchronous & works on separate isolate & thus, performant.
///
/// This is specifically used in the native notifications i.e. System Media Transport Controls, MPRIS & Android Media Session.
///
Future<Uint8List?> imageCropSquare(dynamic image) async {
  final receivePort = ReceivePort();
  await Isolate.spawn(
    _cropSquareIsolate,
    _DecodeParam(
      image,
      receivePort.sendPort,
    ),
  );
  final result = await receivePort.first;
  receivePort.close();
  assert(result is Uint8List || result == null);
  return result;
}

/// Used for packing parameters for [_cropSquareIsolate] method.
class _DecodeParam {
  final dynamic image;
  final SendPort sendPort;
  _DecodeParam(
    this.image,
    this.sendPort,
  );
}

/// Method spawned on another isolate for [imageCropSquare].
///
/// Returns `null` if passed [data.image] is in unknown format or
/// original image if some other error is received.
///
void _cropSquareIsolate(_DecodeParam data) async {
  Uint8List? buffer;
  if (data.image is Uint8List || data.image is List<int>) {
    buffer = data.image;
  } else if (data.image is Uri || data.image is String) {
    try {
      final response = await http.get(
        data.image is Uri ? data.image : Uri.parse(data.image),
      );
      buffer = response.bodyBytes;
    } catch (exception, stacktrace) {
      debugPrint(exception.toString());
      debugPrint(stacktrace.toString());
    }
  } else if (data.image is File) {
    try {
      buffer = await (data.image as File).readAsBytes_();
    } catch (exception, stacktrace) {
      debugPrint(exception.toString());
      debugPrint(stacktrace.toString());
    }
  }
  if (buffer != null) {
    try {
      final image = decodeImage(buffer);
      if (image != null && image.width != 0 && image.height != 0) {
        final dimension = min(image.width, image.height);
        final result = copyResizeCropSquare(image, dimension);
        data.sendPort.send(encodeJpg(result));
      }
      return data.sendPort.send(buffer);
    } catch (exception, stacktrace) {
      debugPrint(exception.toString());
      debugPrint(stacktrace.toString());
    }
  }
  data.sendPort.send(null);
}