Merge pull request #2641 from RobertMut/main

Add JPEG COM marker support

Author: JimBobSquarePants

ImageSharp.sln

@@ -238,6 +238,7 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "issues", "issues", "{5C9B68
 		tests\Images\Input\Jpg\issues\issue750-exif-tranform.jpg = tests\Images\Input\Jpg\issues\issue750-exif-tranform.jpg
 		tests\Images\Input\Jpg\issues\Issue845-Incorrect-Quality99.jpg = tests\Images\Input\Jpg\issues\Issue845-Incorrect-Quality99.jpg
 		tests\Images\Input\Jpg\issues\issue855-incorrect-colorspace.jpg = tests\Images\Input\Jpg\issues\issue855-incorrect-colorspace.jpg
+		tests\Images\Input\Jpg\issues\issue-2067-comment.jpg = tests\Images\Input\Jpg\issues\issue-2067-comment.jpg
 	EndProjectSection
 EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "fuzz", "fuzz", "{516A3532-6AC2-417B-AD79-9BD5D0D378A0}"

src/ImageSharp/Formats/Jpeg/JpegComData.cs

@@ -0,0 +1,32 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+namespace SixLabors.ImageSharp.Formats.Jpeg;
+
+/// <summary>
+/// Represents a JPEG comment
+/// </summary>
+public readonly struct JpegComData
+{
+    /// <summary>
+    /// Initializes a new instance of the <see cref="JpegComData"/> struct.
+    /// </summary>
+    /// <param name="value">The comment buffer.</param>
+    public JpegComData(ReadOnlyMemory<char> value)
+        => this.Value = value;
+
+    /// <summary>
+    /// Gets the value.
+    /// </summary>
+    public ReadOnlyMemory<char> Value { get; }
+
+    /// <summary>
+    /// Converts string to <see cref="JpegComData"/>
+    /// </summary>
+    /// <param name="value">The comment string.</param>
+    /// <returns>The <see cref="JpegComData"/></returns>
+    public static JpegComData FromString(string value) => new(value.AsMemory());
+
+    /// <inheritdoc/>
+    public override string ToString() => this.Value.ToString();
+}

src/ImageSharp/Formats/Jpeg/JpegDecoderCore.cs

@@ -480,9 +480,11 @@ internal void ParseStream(BufferedReadStream stream, SpectralConverter spectralC
                         break;
 
                     case JpegConstants.Markers.APP15:
-                    case JpegConstants.Markers.COM:
                         stream.Skip(markerContentByteSize);
                         break;
+                    case JpegConstants.Markers.COM:
+                        this.ProcessComMarker(stream, markerContentByteSize);
+                        break;
 
                     case JpegConstants.Markers.DAC:
                         if (metadataOnly)
@@ -515,6 +517,25 @@ public void Dispose()
         this.scanDecoder = null;
     }
 
+    /// <summary>
+    /// Assigns COM marker bytes to comment property
+    /// </summary>
+    /// <param name="stream">The input stream.</param>
+    /// <param name="markerContentByteSize">The remaining bytes in the segment block.</param>
+    private void ProcessComMarker(BufferedReadStream stream, int markerContentByteSize)
+    {
+        char[] chars = new char[markerContentByteSize];
+        JpegMetadata metadata = this.Metadata.GetFormatMetadata(JpegFormat.Instance);
+
+        for (int i = 0; i < markerContentByteSize; i++)
+        {
+            int read = stream.ReadByte();
+            chars[i] = (char)read;
+        }
+
+        metadata.Comments.Add(new JpegComData(chars));
+    }
+
     /// <summary>
     /// Returns encoded colorspace based on the adobe APP14 marker.
     /// </summary>

src/ImageSharp/Formats/Jpeg/JpegEncoderCore.cs

@@ -2,6 +2,7 @@
 // Licensed under the Six Labors Split License.
 #nullable disable
 
+using System.Buffers;
 using System.Buffers.Binary;
 using SixLabors.ImageSharp.Common.Helpers;
 using SixLabors.ImageSharp.Formats.Jpeg.Components;
@@ -25,6 +26,9 @@ internal sealed unsafe partial class JpegEncoderCore : IImageEncoderInternals
     /// </summary>
     private static readonly JpegFrameConfig[] FrameConfigs = CreateFrameConfigs();
 
+    /// <summary>
+    /// The current calling encoder.
+    /// </summary>
     private readonly JpegEncoder encoder;
 
     /// <summary>
@@ -89,6 +93,9 @@ public void Encode<TPixel>(Image<TPixel> image, Stream stream, CancellationToken
         // Write Exif, XMP, ICC and IPTC profiles
         this.WriteProfiles(metadata, buffer);
 
+        // Write comments
+        this.WriteComments(image.Configuration, jpegMetadata);
+
         // Write the image dimensions.
         this.WriteStartOfFrame(image.Width, image.Height, frameConfig, buffer);
 
@@ -167,6 +174,51 @@ private void WriteJfifApplicationHeader(ImageMetadata meta, Span<byte> buffer)
         this.outputStream.Write(buffer, 0, 18);
     }
 
+    /// <summary>
+    /// Writes the COM tags.
+    /// </summary>
+    /// <param name="configuration">The configuration.</param>
+    /// <param name="metadata">The image metadata.</param>
+    private void WriteComments(Configuration configuration, JpegMetadata metadata)
+    {
+        if (metadata.Comments.Count == 0)
+        {
+            return;
+        }
+
+        const int maxCommentLength = 65533;
+        using IMemoryOwner<byte> bufferOwner = configuration.MemoryAllocator.Allocate<byte>(maxCommentLength);
+        Span<byte> buffer = bufferOwner.Memory.Span;
+        foreach (JpegComData comment in metadata.Comments)
+        {
+            int totalLength = comment.Value.Length;
+            if (totalLength == 0)
+            {
+                continue;
+            }
+
+            // Loop through and split the comment into multiple comments if the comment length
+            // is greater than the maximum allowed length.
+            while (totalLength > 0)
+            {
+                int currentLength = Math.Min(totalLength, maxCommentLength);
+
+                // Write the marker header.
+                this.WriteMarkerHeader(JpegConstants.Markers.COM, currentLength + 2, buffer);
+
+                ReadOnlySpan<char> commentValue = comment.Value.Span.Slice(comment.Value.Length - totalLength, currentLength);
+                for (int i = 0; i < commentValue.Length; i++)
+                {
+                    buffer[i] = (byte)commentValue[i];
+                }
+
+                // Write the comment.
+                this.outputStream.Write(buffer, 0, currentLength);
+                totalLength -= currentLength;
+            }
+        }
+    }
+
     /// <summary>
     /// Writes the Define Huffman Table marker and tables.
     /// </summary>

src/ImageSharp/Formats/Jpeg/JpegMetadata.cs

@@ -15,6 +15,7 @@ public class JpegMetadata : IDeepCloneable
     /// </summary>
     public JpegMetadata()
     {
+        this.Comments = new List<JpegComData>();
     }
 
     /// <summary>
@@ -25,6 +26,7 @@ private JpegMetadata(JpegMetadata other)
     {
         this.ColorType = other.ColorType;
 
+        this.Comments = other.Comments;
         this.LuminanceQuality = other.LuminanceQuality;
         this.ChrominanceQuality = other.ChrominanceQuality;
     }
@@ -101,6 +103,11 @@ public int Quality
     /// </remarks>
     public bool? Progressive { get; internal set; }
 
+    /// <summary>
+    /// Gets the comments.
+    /// </summary>
+    public IList<JpegComData> Comments { get; }
+
     /// <inheritdoc/>
     public IDeepCloneable DeepClone() => new JpegMetadata(this);
 }

src/ImageSharp/Formats/Jpeg/MetadataExtensions.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
 
+using System.Text;
 using SixLabors.ImageSharp.Formats.Jpeg;
 using SixLabors.ImageSharp.Metadata;
 

tests/ImageSharp.Tests/Formats/Jpg/JpegDecoderTests.Metadata.cs

@@ -425,6 +425,21 @@ public void EncodedStringTags_Read()
         VerifyEncodedStrings(exif);
     }
 
+    [Theory]
+    [WithFile(TestImages.Jpeg.Issues.Issue2067_CommentMarker, PixelTypes.Rgba32)]
+    public void JpegDecoder_DecodeMetadataComment<TPixel>(TestImageProvider<TPixel> provider)
+        where TPixel : unmanaged, IPixel<TPixel>
+    {
+        string expectedComment = "TEST COMMENT";
+        using Image<TPixel> image = provider.GetImage(JpegDecoder.Instance);
+        JpegMetadata metadata = image.Metadata.GetJpegMetadata();
+
+        Assert.Equal(1, metadata.Comments.Count);
+        Assert.Equal(expectedComment, metadata.Comments.ElementAtOrDefault(0).ToString());
+        image.DebugSave(provider);
+        image.CompareToOriginal(provider);
+    }
+
     private static void VerifyEncodedStrings(ExifProfile exif)
     {
         Assert.NotNull(exif);