mirror of
https://github.com/vodemn/m3_lightmeter.git
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20 lines
892 B
Dart
20 lines
892 B
Dart
import 'dart:math' as math;
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import 'package:exif/exif.dart';
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import 'package:flutter/foundation.dart';
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import 'package:m3_lightmeter_resources/m3_lightmeter_resources.dart';
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Future<double> evFromImage(Uint8List bytes) async {
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final tags = await readExifFromBytes(bytes);
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final iso = double.tryParse("${tags["EXIF ISOSpeedRatings"]}");
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final apertureValueRatio = (tags["EXIF FNumber"]?.values as IfdRatios?)?.ratios.first;
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final speedValueRatio = (tags["EXIF ExposureTime"]?.values as IfdRatios?)?.ratios.first;
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if (iso == null || apertureValueRatio == null || speedValueRatio == null) {
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throw FlutterError('Error parsing EXIF: ${tags.keys}');
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}
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final aperture = apertureValueRatio.numerator / apertureValueRatio.denominator;
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final speed = speedValueRatio.numerator / speedValueRatio.denominator;
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return log2(math.pow(aperture, 2)) - log2(speed) - log2(iso / 100);
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}
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