Ignore unknown chunks, fixes #2243

src/ImageSharp/Formats/Webp/WebpDecoderCore.cs

@@ -221,7 +221,9 @@ internal sealed class WebpDecoderCore : IImageDecoderInternals, IDisposable
                     }
                     else
                     {
-                        WebpThrowHelper.ThrowImageFormatException("Unexpected chunk followed VP8X header");
+                        // Ignore unknown chunks.
+                        uint chunkSize = this.ReadChunkSize();
+                        this.currentStream.Skip((int)chunkSize);
                     }
                 }
 

tests/ImageSharp.Tests/Formats/WebP/WebpDecoderTests.cs

@@ -385,6 +385,17 @@ public class WebpDecoderTests
         image.CompareToOriginal(provider, ReferenceDecoder);
     }
 
+    // https://github.com/SixLabors/ImageSharp/issues/2243
+    [Theory]
+    [WithFile(Lossy.Issue2243, PixelTypes.Rgba32)]
+    public void WebpDecoder_CanDecode_Issue2243<TPixel>(TestImageProvider<TPixel> provider)
+        where TPixel : unmanaged, IPixel<TPixel>
+    {
+        using Image<TPixel> image = provider.GetImage(WebpDecoder);
+        image.DebugSave(provider);
+        image.CompareToOriginal(provider, ReferenceDecoder);
+    }
+
     [Theory]
     [WithFile(Lossless.LossLessCorruptImage3, PixelTypes.Rgba32)]
     public void WebpDecoder_ThrowImageFormatException_OnInvalidImages<TPixel>(TestImageProvider<TPixel> provider)

tests/ImageSharp.Tests/TestImages.cs

@@ -736,6 +736,7 @@ public static class TestImages
 
             // Issues
             public const string Issue1594 = "Webp/issues/Issue1594.webp";
+            public const string Issue2243 = "Webp/issues/Issue2243.webp";
         }
     }
 

tests/Images/Input/Webp/issues/Issue2243.webp

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:c1aae55fae66f3f9469ad5e28eb8134a04b1c5d746acf0a4a19d0f63ca0581cd
+size 55068