import 'dart:math'; import 'package:flutter_bloc/flutter_bloc.dart'; import 'package:lightmeter/models/aperture_value.dart'; import 'package:lightmeter/models/exposure_pair.dart'; import 'package:lightmeter/models/iso_value.dart'; import 'package:lightmeter/models/nd_value.dart'; import 'package:lightmeter/models/photography_value.dart'; import 'package:lightmeter/models/shutter_speed_value.dart'; import 'package:lightmeter/utils/log_2.dart'; import 'metering_event.dart'; import 'metering_state.dart'; class MeteringBloc extends Bloc { final StopType stopType; late final _apertureValues = apertureValues.whereStopType(stopType); late final _shutterSpeedValues = shutterSpeedValues.whereStopType(stopType); late final _isoValues = isoValues.whereStopType(stopType); final _random = Random(); MeteringBloc(this.stopType) : super( MeteringState( iso: isoValues.where((element) => element.value == 100).first, ev: 21.3, evCompensation: 0.0, nd: ndValues.first, exposurePairs: [], ), ) { on(_onIsoChanged); on(_onNdChanged); on(_onMeasure); add(const MeasureEvent()); } void _onIsoChanged(IsoChangedEvent event, Emitter emit) { final ev = state.ev + log2(event.isoValue.value / state.iso.value); emit(MeteringState( iso: event.isoValue, ev: ev, evCompensation: state.evCompensation, nd: state.nd, exposurePairs: _buildExposureValues(ev), )); } void _onNdChanged(NdChangedEvent event, Emitter emit) { final ev = state.ev - event.ndValue.stopReduction + state.nd.stopReduction; emit(MeteringState( iso: state.iso, ev: ev, evCompensation: state.evCompensation, nd: event.ndValue, exposurePairs: _buildExposureValues(ev), )); } /// https://www.scantips.com/lights/exposurecalc.html void _onMeasure(_, Emitter emit) { final aperture = _apertureValues[_random.nextInt(_apertureValues.length)]; final shutterSpeed = _shutterSpeedValues[_random.nextInt(_shutterSpeedValues.thirdStops().length)]; final iso = _isoValues[_random.nextInt(_isoValues.thirdStops().length)]; final evAtSystemIso = log2(pow(aperture.value, 2).toDouble() / shutterSpeed.value); final ev = evAtSystemIso - log2(iso.value / state.iso.value); emit(MeteringState( iso: state.iso, ev: ev, evCompensation: state.evCompensation, nd: state.nd, exposurePairs: _buildExposureValues(ev), )); } List _buildExposureValues(double ev) { late final int evSteps; switch (stopType) { case StopType.full: evSteps = ev.floor(); break; case StopType.half: evSteps = (ev / 0.5).floor(); break; case StopType.third: evSteps = (ev / 0.3).floor(); break; } final evOffset = _shutterSpeedValues.indexOf(const ShutterSpeedValue(1, false, StopType.full)) - evSteps; late final int apertureOffset; late final int shutterSpeedOffset; if (evOffset >= 0) { apertureOffset = 0; shutterSpeedOffset = evOffset; } else { apertureOffset = -evOffset; shutterSpeedOffset = 0; } int itemsCount = min(_apertureValues.length + shutterSpeedOffset, _shutterSpeedValues.length + apertureOffset) - max(apertureOffset, shutterSpeedOffset); if (itemsCount < 0) { return List.empty(growable: false); } return List.generate( itemsCount, (index) => ExposurePair( _apertureValues[index + apertureOffset], _shutterSpeedValues[index + shutterSpeedOffset], ), growable: false, ); } }