Fix #2992

JimBobSquarePants · JimBobSquarePants · commit 9443543ae8a1 · 2025-10-23T23:17:07.000+10:00
diff --git a/src/ImageSharp/Formats/Webp/WebpAnimationDecoder.cs b/src/ImageSharp/Formats/Webp/WebpAnimationDecoder.cs
@@ -32,6 +32,11 @@ internal class WebpAnimationDecoder : IDisposable
     /// </summary>
     private readonly uint maxFrames;
 
+    /// <summary>
+    /// Whether to skip metadata.
+    /// </summary>
+    private readonly bool skipMetadata;
+
     /// <summary>
     /// The area to restore.
     /// </summary>
@@ -63,15 +68,85 @@ internal class WebpAnimationDecoder : IDisposable
     /// <param name="memoryAllocator">The memory allocator.</param>
     /// <param name="configuration">The global configuration.</param>
     /// <param name="maxFrames">The maximum number of frames to decode. Inclusive.</param>
+    /// <param name="skipMetadata">Whether to skip metadata.</param>
     /// <param name="backgroundColorHandling">The flag to decide how to handle the background color in the Animation Chunk.</param>
-    public WebpAnimationDecoder(MemoryAllocator memoryAllocator, Configuration configuration, uint maxFrames, BackgroundColorHandling backgroundColorHandling)
+    public WebpAnimationDecoder(
+        MemoryAllocator memoryAllocator,
+        Configuration configuration,
+        uint maxFrames,
+        bool skipMetadata,
+        BackgroundColorHandling backgroundColorHandling)
     {
         this.memoryAllocator = memoryAllocator;
         this.configuration = configuration;
         this.maxFrames = maxFrames;
+        this.skipMetadata = skipMetadata;
         this.backgroundColorHandling = backgroundColorHandling;
     }
 
+    /// <summary>
+    /// Reads the animated webp image information from the specified stream.
+    /// </summary>
+    /// <param name="stream">The stream, where the image should be decoded from. Cannot be null.</param>
+    /// <param name="bitsPerPixel">The bits per pixel.</param>
+    /// <param name="features">The webp features.</param>
+    /// <param name="width">The width of the image.</param>
+    /// <param name="height">The height of the image.</param>
+    /// <param name="completeDataSize">The size of the image data in bytes.</param>
+    public ImageInfo Identify(
+        BufferedReadStream stream,
+        int bitsPerPixel,
+        WebpFeatures features,
+        uint width,
+        uint height,
+        uint completeDataSize)
+    {
+        List<ImageFrameMetadata> framesMetadata = new();
+        this.metadata = new ImageMetadata();
+        this.webpMetadata = this.metadata.GetWebpMetadata();
+        this.webpMetadata.RepeatCount = features.AnimationLoopCount;
+
+        this.webpMetadata.BackgroundColor = this.backgroundColorHandling == BackgroundColorHandling.Ignore
+            ? Color.Transparent
+            : features.AnimationBackgroundColor!.Value;
+
+        Span<byte> buffer = stackalloc byte[4];
+        uint frameCount = 0;
+        int remainingBytes = (int)completeDataSize;
+        while (remainingBytes > 0)
+        {
+            WebpChunkType chunkType = WebpChunkParsingUtils.ReadChunkType(stream, buffer);
+            remainingBytes -= 4;
+            switch (chunkType)
+            {
+                case WebpChunkType.FrameData:
+
+                    ImageFrameMetadata frameMetadata = new();
+                    uint dataSize = ReadFrameInfo(stream, ref frameMetadata);
+                    framesMetadata.Add(frameMetadata);
+
+                    remainingBytes -= (int)dataSize;
+                    break;
+                case WebpChunkType.Xmp:
+                case WebpChunkType.Exif:
+                    WebpChunkParsingUtils.ParseOptionalChunks(stream, chunkType, this.metadata, this.skipMetadata, buffer);
+                    break;
+                default:
+
+                    // Specification explicitly states to ignore unknown chunks.
+                    // We do not support writing these chunks at present.
+                    break;
+            }
+
+            if (stream.Position == stream.Length || ++frameCount == this.maxFrames)
+            {
+                break;
+            }
+        }
+
+        return new ImageInfo(new PixelTypeInfo(bitsPerPixel), new Size((int)width, (int)height), this.metadata, framesMetadata);
+    }
+
     /// <summary>
     /// Decodes the animated webp image from the specified stream.
     /// </summary>
@@ -127,10 +202,12 @@ public Image<TPixel> Decode<TPixel>(
                     break;
                 case WebpChunkType.Xmp:
                 case WebpChunkType.Exif:
-                    WebpChunkParsingUtils.ParseOptionalChunks(stream, chunkType, image!.Metadata, false, buffer);
+                    WebpChunkParsingUtils.ParseOptionalChunks(stream, chunkType, image!.Metadata, this.skipMetadata, buffer);
                     break;
                 default:
-                    WebpThrowHelper.ThrowImageFormatException("Read unexpected webp chunk data");
+
+                    // Specification explicitly states to ignore unknown chunks.
+                    // We do not support writing these chunks at present.
                     break;
             }
 
@@ -143,6 +220,26 @@ public Image<TPixel> Decode<TPixel>(
         return image!;
     }
 
+    /// <summary>
+    /// Reads frame information from the specified stream and updates the provided frame metadata.
+    /// </summary>
+    /// <param name="stream">The stream from which to read the frame information. Must support reading and seeking.</param>
+    /// <param name="frameMetadata">A reference to the structure that will be updated with the parsed frame metadata.</param>
+    /// <returns>The number of bytes read from the stream while parsing the frame information.</returns>
+    private static uint ReadFrameInfo(BufferedReadStream stream, ref ImageFrameMetadata frameMetadata)
+    {
+        WebpFrameData frameData = WebpFrameData.Parse(stream);
+        SetFrameMetadata(frameMetadata, frameData);
+
+        // Size of the frame header chunk.
+        const int chunkHeaderSize = 16;
+
+        uint remaining = frameData.DataSize - chunkHeaderSize;
+        stream.Skip((int)remaining);
+
+        return remaining;
+    }
+
     /// <summary>
     /// Reads an individual webp frame.
     /// </summary>
diff --git a/src/ImageSharp/Formats/Webp/WebpChunkParsingUtils.cs b/src/ImageSharp/Formats/Webp/WebpChunkParsingUtils.cs
@@ -2,6 +2,7 @@
 // Licensed under the Six Labors Split License.
 
 using System.Buffers.Binary;
+using SixLabors.ImageSharp.Common.Helpers;
 using SixLabors.ImageSharp.Formats.Webp.BitReader;
 using SixLabors.ImageSharp.Formats.Webp.Lossy;
 using SixLabors.ImageSharp.IO;
@@ -345,7 +346,20 @@ public static void ParseOptionalChunks(BufferedReadStream stream, WebpChunkType
 
                     if (metadata.ExifProfile != null)
                     {
-                        metadata.ExifProfile = new ExifProfile(exifData);
+                        ExifProfile exifProfile = new(exifData);
+
+                        // Set the resolution from the metadata.
+                        double horizontalValue = GetExifResolutionValue(exifProfile, ExifTag.XResolution);
+                        double verticalValue = GetExifResolutionValue(exifProfile, ExifTag.YResolution);
+
+                        if (horizontalValue > 0 && verticalValue > 0)
+                        {
+                            metadata.HorizontalResolution = horizontalValue;
+                            metadata.VerticalResolution = verticalValue;
+                            metadata.ResolutionUnits = UnitConverter.ExifProfileToResolutionUnit(exifProfile);
+                        }
+
+                        metadata.ExifProfile = exifProfile;
                     }
 
                     break;
@@ -370,6 +384,16 @@ public static void ParseOptionalChunks(BufferedReadStream stream, WebpChunkType
         }
     }
 
+    private static double GetExifResolutionValue(ExifProfile exifProfile, ExifTag<Rational> tag)
+    {
+        if (exifProfile.TryGetValue(tag, out IExifValue<Rational>? resolution))
+        {
+            return resolution.Value.ToDouble();
+        }
+
+        return 0;
+    }
+
     /// <summary>
     /// Determines if the chunk type is an optional VP8X chunk.
     /// </summary>
diff --git a/src/ImageSharp/Formats/Webp/WebpDecoderCore.cs b/src/ImageSharp/Formats/Webp/WebpDecoderCore.cs
@@ -89,7 +89,9 @@ protected override Image<TPixel> Decode<TPixel>(BufferedReadStream stream, Cance
                         this.memoryAllocator,
                         this.configuration,
                         this.maxFrames,
+                        this.skipMetadata,
                         this.backgroundColorHandling);
+
                     return animationDecoder.Decode<TPixel>(stream, this.webImageInfo.Features, this.webImageInfo.Width, this.webImageInfo.Height, fileSize);
                 }
 
@@ -101,6 +103,7 @@ protected override Image<TPixel> Decode<TPixel>(BufferedReadStream stream, Cance
                         this.webImageInfo.Vp8LBitReader,
                         this.memoryAllocator,
                         this.configuration);
+
                     losslessDecoder.Decode(pixels, image.Width, image.Height);
                 }
                 else
@@ -109,6 +112,7 @@ protected override Image<TPixel> Decode<TPixel>(BufferedReadStream stream, Cance
                         this.webImageInfo.Vp8BitReader,
                         this.memoryAllocator,
                         this.configuration);
+
                     lossyDecoder.Decode(pixels, image.Width, image.Height, this.webImageInfo, this.alphaData);
                 }
 
@@ -131,11 +135,29 @@ protected override Image<TPixel> Decode<TPixel>(BufferedReadStream stream, Cance
     /// <inheritdoc />
     protected override ImageInfo Identify(BufferedReadStream stream, CancellationToken cancellationToken)
     {
-        ReadImageHeader(stream, stackalloc byte[4]);
-
+        uint fileSize = ReadImageHeader(stream, stackalloc byte[4]);
         ImageMetadata metadata = new();
+
         using (this.webImageInfo = this.ReadVp8Info(stream, metadata, true))
         {
+            if (this.webImageInfo.Features is { Animation: true })
+            {
+                using WebpAnimationDecoder animationDecoder = new(
+                    this.memoryAllocator,
+                    this.configuration,
+                    this.maxFrames,
+                    this.skipMetadata,
+                    this.backgroundColorHandling);
+
+                return animationDecoder.Identify(
+                    stream,
+                    (int)this.webImageInfo.BitsPerPixel,
+                    this.webImageInfo.Features,
+                    this.webImageInfo.Width,
+                    this.webImageInfo.Height,
+                    fileSize);
+            }
+
             return new ImageInfo(
                 new PixelTypeInfo((int)this.webImageInfo.BitsPerPixel),
                 new Size((int)this.webImageInfo.Width, (int)this.webImageInfo.Height),
@@ -208,6 +230,8 @@ private WebpImageInfo ReadVp8Info(BufferedReadStream stream, ImageMetadata metad
                     }
                     else if (WebpChunkParsingUtils.IsOptionalVp8XChunk(chunkType))
                     {
+                        // ANIM chunks appear before EXIF and XMP chunks.
+                        // Return after parsing an ANIM chunk - The animated decoder will handle the rest.
                         bool isAnimationChunk = this.ParseOptionalExtendedChunks(stream, metadata, chunkType, features, ignoreAlpha, buffer);
                         if (isAnimationChunk)
                         {
diff --git a/tests/ImageSharp.Tests/Formats/WebP/WebpDecoderTests.cs b/tests/ImageSharp.Tests/Formats/WebP/WebpDecoderTests.cs
@@ -314,6 +314,21 @@ public void Decode_AnimatedLossless_VerifyAllFrames<TPixel>(TestImageProvider<TP
         Assert.Equal(12, image.Frames.Count);
     }
 
+    [Theory]
+    [InlineData(Lossless.Animated)]
+    public void Info_AnimatedLossless_VerifyAllFrames(string imagePath)
+    {
+        TestFile testFile = TestFile.Create(imagePath);
+        using MemoryStream stream = new(testFile.Bytes, false);
+        ImageInfo image = WebpDecoder.Instance.Identify(DecoderOptions.Default, stream);
+        WebpMetadata webpMetaData = image.Metadata.GetWebpMetadata();
+        WebpFrameMetadata frameMetaData = image.FrameMetadataCollection[0].GetWebpMetadata();
+
+        Assert.Equal(0, webpMetaData.RepeatCount);
+        Assert.Equal(150U, frameMetaData.FrameDelay);
+        Assert.Equal(12, image.FrameMetadataCollection.Count);
+    }
+
     [Theory]
     [WithFile(Lossy.Animated, PixelTypes.Rgba32)]
     public void Decode_AnimatedLossy_VerifyAllFrames<TPixel>(TestImageProvider<TPixel> provider)
@@ -331,6 +346,21 @@ public void Decode_AnimatedLossy_VerifyAllFrames<TPixel>(TestImageProvider<TPixe
         Assert.Equal(12, image.Frames.Count);
     }
 
+    [Theory]
+    [InlineData(Lossy.Animated)]
+    public void Info_AnimatedLossy_VerifyAllFrames(string imagePath)
+    {
+        TestFile testFile = TestFile.Create(imagePath);
+        using MemoryStream stream = new(testFile.Bytes, false);
+        ImageInfo image = WebpDecoder.Instance.Identify(DecoderOptions.Default, stream);
+        WebpMetadata webpMetaData = image.Metadata.GetWebpMetadata();
+        WebpFrameMetadata frameMetaData = image.FrameMetadataCollection[0].GetWebpMetadata();
+
+        Assert.Equal(0, webpMetaData.RepeatCount);
+        Assert.Equal(150U, frameMetaData.FrameDelay);
+        Assert.Equal(12, image.FrameMetadataCollection.Count);
+    }
+
     [Theory]
     [WithFile(Lossless.Animated, PixelTypes.Rgba32)]
     public void Decode_AnimatedLossless_WithFrameDecodingModeFirst_OnlyDecodesOneFrame<TPixel>(TestImageProvider<TPixel> provider)
