m3_lightmeter/lib/data/ev_source/camera/bloc_camera.dart

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import 'dart:async';
import 'dart:io';
import 'dart:math';
import 'dart:typed_data';
import 'package:camera/camera.dart';
import 'package:exif/exif.dart';
import 'package:flutter/widgets.dart';
import 'package:flutter_bloc/flutter_bloc.dart';
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import 'package:lightmeter/data/ev_source/ev_source_bloc.dart';
import 'package:lightmeter/screens/metering/communication/bloc_communication_metering.dart';
import 'package:lightmeter/screens/metering/communication/event_communication_metering.dart' as communication_event;
import 'package:lightmeter/screens/metering/communication/state_communication_metering.dart' as communication_states;
import 'package:lightmeter/utils/log_2.dart';
import 'event_camera.dart';
import 'state_camera.dart';
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class CameraBloc extends EvSourceBloc<CameraEvent, CameraState> {
late final _WidgetsBindingObserver _observer;
CameraController? _cameraController;
CameraController? get cameraController => _cameraController;
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CameraBloc(MeteringCommunicationBloc communicationBloc)
: super(
communicationBloc,
const CameraInitState(),
) {
_observer = _WidgetsBindingObserver(_appLifecycleStateObserver);
WidgetsBinding.instance.addObserver(_observer);
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on<InitializeEvent>(_onInitialize);
add(const InitializeEvent());
}
@override
Future<void> close() async {
WidgetsBinding.instance.removeObserver(_observer);
_cameraController?.dispose();
super.close();
}
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@override
void onCommunicationState(communication_states.SourceState communicationState) {
if (communicationState is communication_states.MeasureState) {
_takePhoto().then((ev100) {
if (ev100 != null) {
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communicationBloc.add(communication_event.MeasuredEvent(ev100));
}
});
}
}
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Future<void> _onInitialize(_, Emitter emit) async {
emit(const CameraLoadingState());
try {
final cameras = await availableCameras();
_cameraController = CameraController(
cameras.firstWhere(
(camera) => camera.lensDirection == CameraLensDirection.back,
orElse: () => cameras.last,
),
ResolutionPreset.medium,
enableAudio: false,
);
await _cameraController!.initialize();
await _cameraController!.setFlashMode(FlashMode.off);
emit(CameraReadyState(_cameraController!));
_takePhoto().then((ev100) {
if (ev100 != null) {
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communicationBloc.add(communication_event.MeasuredEvent(ev100));
}
});
} catch (e) {
emit(const CameraErrorState());
}
}
Future<double?> _takePhoto() async {
if (_cameraController == null ||
!_cameraController!.value.isInitialized ||
_cameraController!.value.isTakingPicture) {
return null;
}
try {
final file = await _cameraController!.takePicture();
final Uint8List bytes = await file.readAsBytes();
Directory(file.path).deleteSync(recursive: true);
final tags = await readExifFromBytes(bytes);
final iso = double.parse("${tags["EXIF ISOSpeedRatings"]}");
final apertureValueRatio = (tags["EXIF FNumber"]!.values as IfdRatios).ratios.first;
final aperture = apertureValueRatio.numerator / apertureValueRatio.denominator;
final speedValueRatio = (tags["EXIF ExposureTime"]!.values as IfdRatios).ratios.first;
final speed = speedValueRatio.numerator / speedValueRatio.denominator;
return log2(pow(aperture, 2)) - log2(speed) - log2(iso / 100);
} on CameraException catch (e) {
debugPrint('Error: ${e.code}\nError Message: ${e.description}');
return null;
}
}
Future<void> _appLifecycleStateObserver(AppLifecycleState state) async {
switch (state) {
case AppLifecycleState.resumed:
add(const InitializeEvent());
break;
case AppLifecycleState.paused:
case AppLifecycleState.inactive:
_cameraController?.dispose();
_cameraController = null;
break;
default:
}
}
}
/// This is needed only because we cannot use `with` with mixins
class _WidgetsBindingObserver with WidgetsBindingObserver {
final ValueChanged<AppLifecycleState> onLifecycleStateChanged;
_WidgetsBindingObserver(this.onLifecycleStateChanged);
@override
void didChangeAppLifecycleState(AppLifecycleState state) {
onLifecycleStateChanged(state);
}
}