Merge pull request #2943 from SixLabors/js/issue-2906

V4 Use EXIF byte order for EXIF encoded strings.

Author: JimBobSquarePants

src/ImageSharp/Formats/Tiff/Ifd/EntryReader.cs

@@ -14,7 +14,7 @@ public EntryReader(Stream stream, ByteOrder byteOrder, MemoryAllocator allocator
         : base(stream, allocator) =>
         this.IsBigEndian = byteOrder == ByteOrder.BigEndian;
 
-    public List<IExifValue> Values { get; } = new();
+    public List<IExifValue> Values { get; } = [];
 
     public ulong NextIfdOffset { get; private set; }
 
@@ -31,8 +31,6 @@ public void ReadTags(bool isBigTiff, ulong ifdOffset)
         {
             this.ReadValues64(this.Values, ifdOffset);
             this.NextIfdOffset = this.ReadUInt64();
-
-            //// this.ReadSubIfd64(this.Values);
         }
     }
 
@@ -62,9 +60,9 @@ public void ReadFileHeader()
         {
             this.IsBigTiff = true;
 
-            ushort bytesize = this.ReadUInt16();
+            ushort byteSize = this.ReadUInt16();
             ushort reserve = this.ReadUInt16();
-            if (bytesize == TiffConstants.BigTiffByteSize && reserve == 0)
+            if (byteSize == TiffConstants.BigTiffByteSize && reserve == 0)
             {
                 this.FirstIfdOffset = this.ReadUInt64();
                 return;

src/ImageSharp/Metadata/Profiles/Exif/ExifDataType.cs

@@ -4,7 +4,7 @@
 namespace SixLabors.ImageSharp.Metadata.Profiles.Exif;
 
 /// <summary>
-/// Specifies exif data types.
+/// Specifies Exif data types.
 /// </summary>
 public enum ExifDataType
 {

src/ImageSharp/Metadata/Profiles/Exif/ExifEncodedStringHelpers.cs

@@ -16,13 +16,13 @@ internal static class ExifEncodedStringHelpers
     private const ulong UnicodeCode = 0x_45_44_4F_43_49_4E_55;
     private const ulong UndefinedCode = 0x_00_00_00_00_00_00_00_00;
 
-    private static ReadOnlySpan<byte> AsciiCodeBytes => new byte[] { 0x41, 0x53, 0x43, 0x49, 0x49, 0, 0, 0 };
+    private static ReadOnlySpan<byte> AsciiCodeBytes => [0x41, 0x53, 0x43, 0x49, 0x49, 0, 0, 0];
 
-    private static ReadOnlySpan<byte> JISCodeBytes => new byte[] { 0x4A, 0x49, 0x53, 0, 0, 0, 0, 0 };
+    private static ReadOnlySpan<byte> JISCodeBytes => [0x4A, 0x49, 0x53, 0, 0, 0, 0, 0];
 
-    private static ReadOnlySpan<byte> UnicodeCodeBytes => new byte[] { 0x55, 0x4E, 0x49, 0x43, 0x4F, 0x44, 0x45, 0 };
+    private static ReadOnlySpan<byte> UnicodeCodeBytes => [0x55, 0x4E, 0x49, 0x43, 0x4F, 0x44, 0x45, 0];
 
-    private static ReadOnlySpan<byte> UndefinedCodeBytes => new byte[] { 0, 0, 0, 0, 0, 0, 0, 0 };
+    private static ReadOnlySpan<byte> UndefinedCodeBytes => [0, 0, 0, 0, 0, 0, 0, 0];
 
     // 20932 EUC-JP Japanese (JIS 0208-1990 and 0212-1990)
     // https://docs.microsoft.com/en-us/dotnet/api/system.text.encoding?view=net-6.0
@@ -50,37 +50,60 @@ private static Encoding JIS0208Encoding
         _ => UndefinedCodeBytes
     };
 
-    public static Encoding GetEncoding(CharacterCode code) => code switch
+    public static Encoding GetEncoding(CharacterCode code, ByteOrder order) => code switch
     {
         CharacterCode.ASCII => Encoding.ASCII,
         CharacterCode.JIS => JIS0208Encoding,
-        CharacterCode.Unicode => Encoding.Unicode,
+        CharacterCode.Unicode => order is ByteOrder.BigEndian ? Encoding.BigEndianUnicode : Encoding.Unicode,
         CharacterCode.Undefined => Encoding.UTF8,
         _ => Encoding.UTF8
     };
 
-    public static bool TryParse(ReadOnlySpan<byte> buffer, out EncodedString encodedString)
+    public static bool TryParse(ReadOnlySpan<byte> buffer, ByteOrder order, out EncodedString encodedString)
     {
         if (TryDetect(buffer, out CharacterCode code))
         {
-            string text = GetEncoding(code).GetString(buffer[CharacterCodeBytesLength..]);
-            encodedString = new EncodedString(code, text);
-            return true;
+            ReadOnlySpan<byte> textBuffer = buffer[CharacterCodeBytesLength..];
+            if (code == CharacterCode.Unicode && textBuffer.Length >= 2)
+            {
+                // Check BOM
+                if (textBuffer.StartsWith((ReadOnlySpan<byte>)[0xFF, 0xFE]))
+                {
+                    // Little-endian BOM
+                    string text = Encoding.Unicode.GetString(textBuffer[2..]);
+                    encodedString = new EncodedString(code, text);
+                    return true;
+                }
+
+                if (textBuffer.StartsWith((ReadOnlySpan<byte>)[0xFE, 0xFF]))
+                {
+                    // Big-endian BOM
+                    string text = Encoding.BigEndianUnicode.GetString(textBuffer[2..]);
+                    encodedString = new EncodedString(code, text);
+                    return true;
+                }
+            }
+
+            {
+                string text = GetEncoding(code, order).GetString(textBuffer);
+                encodedString = new EncodedString(code, text);
+                return true;
+            }
         }
 
         encodedString = default;
         return false;
     }
 
     public static uint GetDataLength(EncodedString encodedString) =>
-        (uint)GetEncoding(encodedString.Code).GetByteCount(encodedString.Text) + CharacterCodeBytesLength;
+        (uint)GetEncoding(encodedString.Code, ByteOrder.LittleEndian).GetByteCount(encodedString.Text) + CharacterCodeBytesLength;
 
     public static int Write(EncodedString encodedString, Span<byte> destination)
     {
         GetCodeBytes(encodedString.Code).CopyTo(destination);
 
         string text = encodedString.Text;
-        int count = Write(GetEncoding(encodedString.Code), text, destination[CharacterCodeBytesLength..]);
+        int count = Write(GetEncoding(encodedString.Code, ByteOrder.LittleEndian), text, destination[CharacterCodeBytesLength..]);
 
         return CharacterCodeBytesLength + count;
     }
@@ -92,8 +115,7 @@ private static bool TryDetect(ReadOnlySpan<byte> buffer, out CharacterCode code)
     {
         if (buffer.Length >= CharacterCodeBytesLength)
         {
-            ulong test = BinaryPrimitives.ReadUInt64LittleEndian(buffer);
-            switch (test)
+            switch (BinaryPrimitives.ReadUInt64LittleEndian(buffer))
             {
                 case AsciiCode:
                     code = CharacterCode.ASCII;
@@ -108,7 +130,8 @@ private static bool TryDetect(ReadOnlySpan<byte> buffer, out CharacterCode code)
                     code = CharacterCode.Undefined;
                     return true;
                 default:
-                    break;
+                    code = default;
+                    return false;
             }
         }
 

src/ImageSharp/Metadata/Profiles/Exif/ExifProfile.cs

@@ -3,7 +3,6 @@
 
 using System.Diagnostics.CodeAnalysis;
 using SixLabors.ImageSharp.PixelFormats;
-using static System.Runtime.InteropServices.JavaScript.JSType;
 
 namespace SixLabors.ImageSharp.Metadata.Profiles.Exif;
 
@@ -48,7 +47,7 @@ public ExifProfile(byte[]? data)
     {
         this.Parts = ExifParts.All;
         this.data = data;
-        this.InvalidTags = Array.Empty<ExifTag>();
+        this.InvalidTags = [];
     }
 
     /// <summary>
@@ -171,7 +170,7 @@ public bool TryCreateThumbnail<TPixel>([NotNullWhen(true)] out Image<TPixel>? im
     /// <summary>
     /// Returns the value with the specified tag.
     /// </summary>
-    /// <param name="tag">The tag of the exif value.</param>
+    /// <param name="tag">The tag of the Exif value.</param>
     /// <param name="exifValue">The value with the specified tag.</param>
     /// <returns>True when found, otherwise false</returns>
     /// <typeparam name="TValueType">The data type of the tag.</typeparam>
@@ -215,7 +214,7 @@ public bool RemoveValue(ExifTag tag)
     /// <summary>
     /// Sets the value of the specified tag.
     /// </summary>
-    /// <param name="tag">The tag of the exif value.</param>
+    /// <param name="tag">The tag of the Exif value.</param>
     /// <param name="value">The value.</param>
     /// <typeparam name="TValueType">The data type of the tag.</typeparam>
     public void SetValue<TValueType>(ExifTag<TValueType> tag, TValueType value)
@@ -234,7 +233,7 @@ public void SetValue<TValueType>(ExifTag<TValueType> tag, TValueType value)
 
         if (this.values.Count == 0)
         {
-            return Array.Empty<byte>();
+            return [];
         }
 
         ExifWriter writer = new(this.values, this.Parts);
@@ -247,7 +246,7 @@ public void SetValue<TValueType>(ExifTag<TValueType> tag, TValueType value)
     /// <summary>
     /// Returns the value with the specified tag.
     /// </summary>
-    /// <param name="tag">The tag of the exif value.</param>
+    /// <param name="tag">The tag of the Exif value.</param>
     /// <returns>The value with the specified tag.</returns>
     internal IExifValue? GetValueInternal(ExifTag tag)
     {
@@ -265,7 +264,7 @@ public void SetValue<TValueType>(ExifTag<TValueType> tag, TValueType value)
     /// <summary>
     /// Sets the value of the specified tag.
     /// </summary>
-    /// <param name="tag">The tag of the exif value.</param>
+    /// <param name="tag">The tag of the Exif value.</param>
     /// <param name="value">The value.</param>
     /// <exception cref="NotSupportedException">Newly created value is null.</exception>
     internal void SetValueInternal(ExifTag tag, object? value)
@@ -279,11 +278,7 @@ internal void SetValueInternal(ExifTag tag, object? value)
             }
         }
 
-        ExifValue? newExifValue = ExifValues.Create(tag);
-        if (newExifValue is null)
-        {
-            throw new NotSupportedException($"Newly created value for tag {tag} is null.");
-        }
+        ExifValue? newExifValue = ExifValues.Create(tag) ?? throw new NotSupportedException($"Newly created value for tag {tag} is null.");
 
         newExifValue.TrySetValue(value);
         this.values.Add(newExifValue);
@@ -349,7 +344,7 @@ private void InitializeValues()
 
         if (this.data is null)
         {
-            this.values = new List<IExifValue>();
+            this.values = [];
             return;
         }
 

src/ImageSharp/Metadata/Profiles/Exif/ExifReader.cs

@@ -34,7 +34,7 @@ public ExifReader(byte[] exifData, MemoryAllocator? allocator)
     /// </returns>
     public List<IExifValue> ReadValues()
     {
-        List<IExifValue> values = new();
+        List<IExifValue> values = [];
 
         // II == 0x4949
         this.IsBigEndian = this.ReadUInt16() != 0x4949;
@@ -64,7 +64,7 @@ private void GetThumbnail(uint offset)
             return;
         }
 
-        List<IExifValue> values = new();
+        List<IExifValue> values = [];
         this.ReadValues(values, offset);
 
         for (int i = 0; i < values.Count; i++)
@@ -90,8 +90,8 @@ internal abstract class BaseExifReader
     private readonly MemoryAllocator? allocator;
     private readonly Stream data;
     private List<ExifTag>? invalidTags;
-
     private List<ulong>? subIfds;
+    private bool isBigEndian;
 
     protected BaseExifReader(Stream stream, MemoryAllocator? allocator)
     {
@@ -104,7 +104,7 @@ protected BaseExifReader(Stream stream, MemoryAllocator? allocator)
     /// <summary>
     /// Gets the invalid tags.
     /// </summary>
-    public IReadOnlyList<ExifTag> InvalidTags => this.invalidTags ?? (IReadOnlyList<ExifTag>)Array.Empty<ExifTag>();
+    public IReadOnlyList<ExifTag> InvalidTags => this.invalidTags ?? (IReadOnlyList<ExifTag>)[];
 
     /// <summary>
     /// Gets or sets the thumbnail length in the byte stream.
@@ -116,9 +116,19 @@ protected BaseExifReader(Stream stream, MemoryAllocator? allocator)
     /// </summary>
     public uint ThumbnailOffset { get; protected set; }
 
-    public bool IsBigEndian { get; protected set; }
+    public bool IsBigEndian
+    {
+        get => this.isBigEndian;
+        protected set
+        {
+            this.isBigEndian = value;
+            this.ByteOrder = value ? ByteOrder.BigEndian : ByteOrder.LittleEndian;
+        }
+    }
+
+    protected ByteOrder ByteOrder { get; private set; }
 
-    public List<(ulong Offset, ExifDataType DataType, ulong NumberOfComponents, ExifValue Exif)> BigValues { get; } = new();
+    public List<(ulong Offset, ExifDataType DataType, ulong NumberOfComponents, ExifValue Exif)> BigValues { get; } = [];
 
     protected void ReadBigValues(List<IExifValue> values)
     {
@@ -486,14 +496,21 @@ private void ReadValue64(List<IExifValue> values, Span<byte> offsetBuffer)
 
     private void Add(IList<IExifValue> values, ExifValue exif, object? value)
     {
-        if (!exif.TrySetValue(value))
+        if (exif is ExifEncodedString encodedString)
+        {
+            if (!encodedString.TrySetValue(value, this.ByteOrder))
+            {
+                return;
+            }
+        }
+        else if (!exif.TrySetValue(value))
         {
             return;
         }
 
         foreach (IExifValue val in values)
         {
-            // to skip duplicates must be used Equals method,
+            // To skip duplicates must be used Equals method,
             // == operator not defined for ExifValue and IExifValue
             if (exif.Equals(val))
             {
@@ -517,10 +534,10 @@ private void Add(IList<IExifValue> values, ExifValue exif, object? value)
     }
 
     private void AddInvalidTag(ExifTag tag)
-        => (this.invalidTags ??= new List<ExifTag>()).Add(tag);
+        => (this.invalidTags ??= []).Add(tag);
 
     private void AddSubIfd(object? val)
-        => (this.subIfds ??= new List<ulong>()).Add(Convert.ToUInt64(val, CultureInfo.InvariantCulture));
+        => (this.subIfds ??= []).Add(Convert.ToUInt64(val, CultureInfo.InvariantCulture));
 
     private void Seek(ulong pos)
         => this.data.Seek((long)pos, SeekOrigin.Begin);

src/ImageSharp/Metadata/Profiles/Exif/ExifWriter.cs

@@ -55,7 +55,7 @@ public byte[] GetData()
 
         if (length == 0)
         {
-            return Array.Empty<byte>();
+            return [];
         }
 
         // two bytes for the byte Order marker 'II' or 'MM', followed by the number 42 (0x2A) and a 0, making 4 bytes total
@@ -197,7 +197,7 @@ private static int WriteInt32(int value, Span<byte> destination, int offset)
 
     private List<IExifValue> GetPartValues(ExifParts part)
     {
-        List<IExifValue> result = new();
+        List<IExifValue> result = [];
 
         if (!EnumUtils.HasFlag(this.allowedParts, part))
         {
@@ -332,7 +332,7 @@ private int WriteData(uint startIndex, List<IExifValue> values, Span<byte> desti
 
     private int WriteHeaders(List<IExifValue> values, Span<byte> destination, int offset)
     {
-        this.dataOffsets = new List<int>();
+        this.dataOffsets = [];
 
         int newOffset = WriteUInt16((ushort)values.Count, destination, offset);
 

src/ImageSharp/Metadata/Profiles/Exif/Tags/ExifTag.cs

@@ -4,7 +4,7 @@
 namespace SixLabors.ImageSharp.Metadata.Profiles.Exif;
 
 /// <summary>
-/// Class that represents an exif tag from the Exif standard 2.31.
+/// Class that represents an Exif tag from the Exif standard 2.31.
 /// </summary>
 public abstract partial class ExifTag : IEquatable<ExifTag>
 {
@@ -16,21 +16,21 @@ public abstract partial class ExifTag : IEquatable<ExifTag>
     /// Converts the specified <see cref="ExifTag"/> to a <see cref="ushort"/>.
     /// </summary>
     /// <param name="tag">The <see cref="ExifTag"/> to convert.</param>
-    public static explicit operator ushort(ExifTag tag) => tag?.value ?? (ushort)ExifTagValue.Unknown;
+    public static explicit operator ushort(ExifTag? tag) => tag?.value ?? (ushort)ExifTagValue.Unknown;
 
     /// <summary>
     /// Determines whether the specified <see cref="ExifTag"/> instances are considered equal.
     /// </summary>
     /// <param name="left">The first <see cref="ExifTag"/> to compare.</param>
     /// <param name="right"> The second <see cref="ExifTag"/> to compare.</param>
-    public static bool operator ==(ExifTag left, ExifTag right) => Equals(left, right);
+    public static bool operator ==(ExifTag? left, ExifTag? right) => left?.Equals(right) == true;
 
     /// <summary>
     /// Determines whether the specified <see cref="ExifTag"/> instances are not considered equal.
     /// </summary>
     /// <param name="left">The first <see cref="ExifTag"/> to compare.</param>
     /// <param name="right"> The second <see cref="ExifTag"/> to compare.</param>
-    public static bool operator !=(ExifTag left, ExifTag right) => !Equals(left, right);
+    public static bool operator !=(ExifTag? left, ExifTag? right) => !(left == right);
 
     /// <inheritdoc/>
     public override bool Equals(object? obj)

src/ImageSharp/Metadata/Profiles/Exif/Values/ExifArrayValue{TValueType}.cs

@@ -43,7 +43,7 @@ public override bool TrySetValue(object? value)
 
         if (type == typeof(TValueType))
         {
-            this.Value = new TValueType[] { (TValueType)value };
+            this.Value = [(TValueType)value];
             return true;
         }