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@drewnoakes
drewnoakes committed Apr 12, 2020
1 parent 9f2f25c commit f15124b
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Showing 7 changed files with 781 additions and 1,251 deletions.
92 changes: 74 additions & 18 deletions MetadataExtractor/ExifTags.cs
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Original file line number Diff line number Diff line change
@@ -1,3 +1,5 @@
// Copyright (c) Drew Noakes and contributors. All Rights Reserved. Licensed under the Apache License, Version 2.0. See LICENSE in the project root for license information.

using System;
using System.Collections.Generic;
using System.Text;
Expand Down Expand Up @@ -160,7 +162,7 @@ public static class ExifTags

public static readonly TiffUInt16Tag MaxSampleValue = new TiffUInt16Tag(0x0119, "Maximum Sample Value");

// TODO the descriptor function for these two tags attempts to read units from the directory, which is not yet available via this new API
// TODO the descriptor function for these two tags attempts to read ResolutionUnit from the directory, which is not yet available via this new API
public static readonly TiffUInt16Tag XResolution = new TiffUInt16Tag(0x011A, "X Resolution");
public static readonly TiffUInt16Tag YResolution = new TiffUInt16Tag(0x011B, "Y Resolution");

Expand Down Expand Up @@ -263,6 +265,7 @@ public static class ExifTags
public static readonly TiffUInt16Tag CfaRepeatPatternDim = new TiffUInt16Tag(0x828D, "CFA Repeat Pattern Dim");

/// <summary>There are two definitions for CFA pattern, I don't know the difference...</summary>
// TODO interpreting this tag requires the value of CfaRepeatPatternDim too
public static readonly TiffUInt16Tag CfaPattern2 = new TiffUInt16Tag(0x828E, "CFA Pattern 2");

public static readonly TiffUInt16Tag BatteryLevel = new TiffUInt16Tag(0x828F, "Battery Level");
Expand All @@ -274,7 +277,8 @@ public static class ExifTags
public static readonly TiffURationalTag ExposureTime = new TiffURationalTag(0x829A, "Exposure Time", (value, format) => $"{value.ToSimpleString()} sec");

/// <summary>The actual F-number(F-stop) of lens when the image was taken.</summary>
public static readonly TiffURationalTag FNumber = new TiffURationalTag(0x829D, "F-Number", DescribeFStop);
public static readonly TiffURationalTag FNumber = new TiffURationalTag(0x829D, "F-Number",
(value, format) => DescribeFStop(PhotographicConversions.ApertureToFStop(value.ToDouble()), format));

// TODO what type is this?
public static readonly TiffUInt16Tag IptcNaa = new TiffUInt16Tag(0x83BB, "Iptc Naa");
Expand Down Expand Up @@ -365,7 +369,7 @@ public static class ExifTags

// TODO is this URational
/// <summary>Average (rough estimate) compression level in JPEG bits per pixel.</summary>
public static readonly RationalTag CompressedAverageBitsPerPixel = new RationalTag(0x9102, "Compressed Average Bits Per Pixel",
public static readonly TiffRationalTag CompressedAverageBitsPerPixel = new TiffRationalTag(0x9102, "Compressed Average Bits Per Pixel",
(r, p) => $"{r.ToSimpleString(provider: p)} bit{(r.IsInteger && r.ToInt32() == 1 ? "" : "s")}/pixel");

/// <summary>Shutter speed by APEX value.</summary>
Expand Down Expand Up @@ -397,18 +401,18 @@ public static class ExifTags

/// <summary>Lens aperture used in an image.</summary>
public static readonly TiffURationalTag Aperture = new TiffURationalTag(0x9202, "Aperture",
(r, p) => DescribeFStop(PhotographicConversions.ApertureToFStop(r)));
(value, p) => DescribeFStop(PhotographicConversions.ApertureToFStop(value.ToDouble()), p));

public static readonly RationalTag BrightnessValue = new RationalTag(0x9203, "Brightness");
public static readonly TiffRationalTag BrightnessValue = new TiffRationalTag(0x9203, "Brightness");

public static readonly RationalTag ExposureBias = new RationalTag(0x9204, "Exposure Bias", (value, format) => string.Format(format, "{0} EV", value.ToSimpleString()));
public static readonly TiffRationalTag ExposureBias = new TiffRationalTag(0x9204, "Exposure Bias", (value, format) => string.Format(format, "{0} EV", value.ToSimpleString()));

/// <summary>Maximum aperture of lens.</summary>
public static readonly RationalTag MaxAperture = new RationalTag(0x9205, "Max Aperture", (value, format) => DescribeFStop(PhotographicConversions.ApertureToFStop(value.ToDouble()), format));
public static readonly TiffRationalTag MaxAperture = new TiffRationalTag(0x9205, "Max Aperture", (value, format) => DescribeFStop(PhotographicConversions.ApertureToFStop(value.ToDouble()), format));

/// <summary>The distance autofocus focused to.</summary>
/// <remarks>Tends to be less accurate as distance increases.</remarks>
public static readonly RationalTag SubjectDistance = new RationalTag(0x9206, "Subject Distance", (value, format) => $"{value.ToDouble():0.0##} metres");
public static readonly TiffRationalTag SubjectDistance = new TiffRationalTag(0x9206, "Subject Distance", (value, format) => $"{value.ToDouble():0.0##} metres");

/// <summary>Exposure metering method.</summary>
public static readonly TiffMappedUInt16Tag MeteringMode = new TiffMappedUInt16Tag(0x9207, "Metering Mode", new Dictionary<int, string>
Expand Down Expand Up @@ -522,10 +526,10 @@ public static class ExifTags
/// <para />
/// The component count for this tag includes all of the bytes needed for the makernote.
/// </remarks>
// TODO should this be public?
// TODO should this be public? probably shouldn't be storing the byte array for makernotes, unless it's unknown (in which case it's in a makernote directory)
public static readonly TiffByteArrayTag Makernote = new TiffByteArrayTag(0x927C, "Makernote");

public static readonly TiffStringTag UserComment = new TiffStringTag(0x9286, "User Comment");
public static readonly TiffStringTag UserComment = new TiffStringTag(0x9286, "User Comment", DescribeUserComment);

public static readonly TiffUInt16Tag SubsecondTime = new TiffUInt16Tag(0x9290, "Subsecond Time");

Expand Down Expand Up @@ -652,7 +656,7 @@ public static class ExifTags

/// <remarks>The digital zoom ratio, or zero if digital zoom was not used.</remarks>
public static readonly TiffURationalTag DigitalZoomRatio = new TiffURationalTag(0xA404, "Digital Zoom Ratio",
(ratio, format) => ratio.Numerator == 0 ? "Digital zoom not used" : ratio.ToSimpleString(format));
(ratio, format) => ratio.Numerator == 0 ? "Digital zoom not used" : ratio.ToSimpleString(provider: format));

/// <summary>
/// The equivalent focal length assuming a 35mm film camera, in millimetres.
Expand Down Expand Up @@ -763,18 +767,18 @@ public static class ExifTags
/// </remarks>
public static readonly TiffURationalArrayTag LensSpecification = new TiffURationalArrayTag(0xA432, "Lens Specification", 4, (values, format) =>
{
if (values.Length != 4 || (values[0] == 0 && values[2] == 0))
if (values.Length != 4 || (values[0].IsZero && values[2].IsZero))
return null;

var sb = new StringBuilder();

sb.AppendFormat(
format,
values[0] == values[1] ? "{0}mm" : "{0}-{1}mm",
values[0].ToSimpleString(format),
values[1].ToSimpleString(format));
values[0].ToSimpleString(provider: format),
values[1].ToSimpleString(provider: format));

if (values[2] != 0)
if (!values[2].IsZero)
{
sb.Append(' ');
sb.AppendFormat(
Expand Down Expand Up @@ -810,11 +814,11 @@ public static class ExifTags
// TODO what type is this?
public static readonly TiffUInt16Tag Lens = new TiffUInt16Tag(0xFDEA, "Lens");

private static string DescribeFStop(double fStop, IFormatProvider p) => string.Format(p, "f/{0:0.0}", fStop);
private static string DescribeFStop(double fStop, IFormatProvider format) => string.Format(format, "f/{0:0.0}", fStop);

private static string DescribeFocalLength(double mm, IFormatProvider p) => string.Format(p, "{0:0.#} mm", mm);
private static string DescribeFocalLength(double mm, IFormatProvider format) => string.Format(format, "{0:0.#} mm", mm);

private static string DescribePixels(int i, IFormatProvider p) => string.Format(p, "{0} pixel{1}", i, i == 1 ? "" : "s");
private static string DescribePixels(int i, IFormatProvider format) => string.Format(format, "{0} pixel{1}", i, i == 1 ? "" : "s");

private static string DescribeVersion(IReadOnlyList<int> components, int majorDigits)
{
Expand All @@ -835,5 +839,57 @@ private static string DescribeVersion(IReadOnlyList<int> components, int majorDi
}
return version.ToString();
}

private static string DescribeUserComment(byte[] bytes, IFormatProvider provider)
{
if (bytes.Length == 0)
return string.Empty;

// TODO use ByteTrie here
// Someone suggested "ISO-8859-1".
var encodingMap = new Dictionary<string, Encoding>
{
["ASCII"] = Encoding.ASCII,
["UTF8"] = Encoding.UTF8,
["UTF7"] = Encoding.UTF7,
["UTF32"] = Encoding.UTF32,
["UNICODE"] = Encoding.Unicode,
["JIS"] = Encoding.GetEncoding("Shift-JIS")
};

try
{
if (bytes.Length >= 10)
{
// TODO no guarantee bytes after the UTF8 name are valid UTF8 -- only read as many as needed
var firstTenBytesString = Encoding.UTF8.GetString(bytes, 0, 10);
// try each encoding name
foreach (var pair in encodingMap)
{
var encodingName = pair.Key;
var encoding = pair.Value;
if (firstTenBytesString.StartsWith(encodingName))
{
// skip any null or blank characters commonly present after the encoding name, up to a limit of 10 from the start
for (var j = encodingName.Length; j < 10; j++)
{
var b = bytes[j];
if (b != '\0' && b != ' ')
{
return encoding.GetString(bytes, j, bytes.Length - j).Trim('\0', ' ');
}
}
return encoding.GetString(bytes, 10, bytes.Length - 10).Trim('\0', ' ');
}
}
}
// special handling fell through, return a plain string representation
return Encoding.UTF8.GetString(bytes, 0, bytes.Length).Trim('\0', ' ');
}
catch
{
return null;
}
}
}
}
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