ente/lib/services/object_detection/object_detection_service.dart

import "dart:isolate";
import "dart:typed_data";

import "package:logging/logging.dart";
import "package:photos/services/object_detection/models/predictions.dart";
import 'package:photos/services/object_detection/models/recognition.dart';
import 'package:photos/services/object_detection/tflite/cocossd_classifier.dart';
import "package:photos/services/object_detection/tflite/mobilenet_classifier.dart";
import "package:photos/services/object_detection/tflite/scene_classifier.dart";
import "package:photos/services/object_detection/utils/isolate_utils.dart";

class ObjectDetectionService {
  static const scoreThreshold = 0.5;

  final _logger = Logger("ObjectDetectionService");

  late CocoSSDClassifier _objectClassifier;
  late MobileNetClassifier _mobileNetClassifier;
  late SceneClassifier _sceneClassifier;

  late IsolateUtils _isolateUtils;

  ObjectDetectionService._privateConstructor();
  bool inInitiated = false;

  Future<void> init() async {
    _isolateUtils = IsolateUtils();
    await _isolateUtils.start();
    try {
      _objectClassifier = CocoSSDClassifier();
    } catch (e, s) {
      _logger.severe("Could not initialize cocossd", e, s);
    }
    try {
      _mobileNetClassifier = MobileNetClassifier();
    } catch (e, s) {
      _logger.severe("Could not initialize mobilenet", e, s);
    }
    try {
      _sceneClassifier = SceneClassifier();
    } catch (e, s) {
      _logger.severe("Could not initialize sceneclassifier", e, s);
    }
    inInitiated = true;
  }

  static ObjectDetectionService instance =
      ObjectDetectionService._privateConstructor();

  Future<List<String>> predict(Uint8List bytes) async {
    try {
      if (!inInitiated) {
        return Future.error("ObjectDetectionService init is not completed");
      }
      final results = <String>{};
      results.addAll(await _getObjects(bytes));
      results.addAll(await _getMobileNetResults(bytes));
      results.addAll(await _getSceneResults(bytes));
      return results.toList();
    } catch (e, s) {
      _logger.severe(e, s);
      rethrow;
    }
  }

  Future<List<String>> _getObjects(Uint8List bytes) async {
    try {
      final isolateData = IsolateData(
        bytes,
        _objectClassifier.interpreter.address,
        _objectClassifier.labels,
        ClassifierType.cocossd,
      );
      return _getPredictions(isolateData);
    } catch (e, s) {
      _logger.severe("Could not run cocossd", e, s);
    }
    return [];
  }

  Future<List<String>> _getMobileNetResults(Uint8List bytes) async {
    try {
      final isolateData = IsolateData(
        bytes,
        _mobileNetClassifier.interpreter.address,
        _mobileNetClassifier.labels,
        ClassifierType.mobilenet,
      );
      return _getPredictions(isolateData);
    } catch (e, s) {
      _logger.severe("Could not run mobilenet", e, s);
    }
    return [];
  }

  Future<List<String>> _getSceneResults(Uint8List bytes) async {
    try {
      final isolateData = IsolateData(
        bytes,
        _sceneClassifier.interpreter.address,
        _sceneClassifier.labels,
        ClassifierType.scenes,
      );
      return _getPredictions(isolateData);
    } catch (e, s) {
      _logger.severe("Could not run scene detection", e, s);
    }
    return [];
  }

  Future<List<String>> _getPredictions(IsolateData isolateData) async {
    final predictions = await _inference(isolateData);
    final Set<String> results = {};
    if (predictions.error == null) {
      for (final Recognition result in predictions.recognitions!) {
        if (result.score > scoreThreshold) {
          results.add(result.label);
        }
      }
      _logger.info(
        "Time taken for " +
            isolateData.type.toString() +
            ": " +
            predictions.stats!.totalElapsedTime.toString() +
            "ms",
      );
    } else {
      _logger.severe(
        "Error while fetching predictions for " + isolateData.type.toString(),
        predictions.error,
      );
    }
    return results.toList();
  }

  /// Runs inference in another isolate
  Future<Predictions> _inference(IsolateData isolateData) async {
    final responsePort = ReceivePort();
    _isolateUtils.sendPort.send(
      isolateData..responsePort = responsePort.sendPort,
    );
    return await responsePort.first;
  }
}