Fix #2154

Author: JimBobSquarePants

src/ImageSharp/Formats/Webp/WebpDecoderCore.cs

@@ -660,14 +660,22 @@ private uint ReadChunkSize()
         /// </summary>
         /// <param name="chunkType">The chunk type.</param>
         /// <returns>True, if its an optional chunk type.</returns>
-        private static bool IsOptionalVp8XChunk(WebpChunkType chunkType) => chunkType switch
+        private static bool IsOptionalVp8XChunk(WebpChunkType chunkType)
         {
-            WebpChunkType.Alpha => true,
-            WebpChunkType.Animation => true,
-            WebpChunkType.Exif => true,
-            WebpChunkType.Iccp => true,
-            WebpChunkType.Xmp => true,
-            _ => false
-        };
+            switch (chunkType)
+            {
+                case WebpChunkType.Alpha:
+                case WebpChunkType.Iccp:
+                case WebpChunkType.Exif:
+                case WebpChunkType.Xmp:
+                    return true;
+                case WebpChunkType.AnimationParameter:
+                case WebpChunkType.Animation:
+                    WebpThrowHelper.ThrowNotSupportedException("Animated webp are not yet supported.");
+                    return false;
+                default:
+                    return false;
+            }
+        }
     }
 }

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

@@ -1,6 +1,7 @@
 // Copyright (c) Six Labors.
 // Licensed under the Apache License, Version 2.0.
 
+using System;
 using System.IO;
 using SixLabors.ImageSharp.Formats.Webp;
 using SixLabors.ImageSharp.PixelFormats;
@@ -369,6 +370,19 @@ public void WebpDecoder_ThrowImageFormatException_OnInvalidImages<TPixel>(TestIm
                     }
                 });
 
+        // https://github.com/SixLabors/ImageSharp/issues/2154
+        [Theory]
+        [WithFile(Lossless.Issue2154, PixelTypes.Rgba32)]
+        public void WebpDecoder_ThrowsNotSupportedException_Issue2154<TPixel>(TestImageProvider<TPixel> provider)
+            where TPixel : unmanaged, IPixel<TPixel> =>
+            Assert.Throws<NotSupportedException>(
+                () =>
+                {
+                    using (provider.GetImage(WebpDecoder))
+                    {
+                    }
+                });
+
 #if SUPPORTS_RUNTIME_INTRINSICS
         private static void RunDecodeLossyWithHorizontalFilter()
         {

tests/ImageSharp.Tests/TestImages.cs

@@ -632,6 +632,9 @@ public static class Lossless
                 public const string LossLessCorruptImage3 = "Webp/lossless_color_transform.webp"; // cross_color, predictor
 
                 public const string LossLessCorruptImage4 = "Webp/near_lossless_75.webp"; // predictor, cross_color.
+
+                // Issues
+                public const string Issue2154 = "Webp/issues/Issue2154.webp";
             }
 
             public static class Lossy