V2 Backport: 2133, 2154

src/ImageSharp/Formats/Jpeg/JpegDecoderCore.cs

@@ -530,6 +530,12 @@ private JpegColorSpace DeduceJpegColorSpace(byte componentCount)
                     return JpegColorSpace.RGB;
                 }
 
+                // If these values are 1-3 for a 3-channel image, then the image is assumed to be YCbCr.
+                if (this.Components[2].Id == 3 && this.Components[1].Id == 2 && this.Components[0].Id == 1)
+                {
+                    return JpegColorSpace.YCbCr;
+                }
+
                 // 3-channel non-subsampled images are assumed to be RGB.
                 if (this.Components[2].VerticalSamplingFactor == 1 && this.Components[1].VerticalSamplingFactor == 1 && this.Components[0].VerticalSamplingFactor == 1 &&
                     this.Components[2].HorizontalSamplingFactor == 1 && this.Components[1].HorizontalSamplingFactor == 1 && this.Components[0].HorizontalSamplingFactor == 1)

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/Jpg/JpegDecoderTests.cs

@@ -216,6 +216,19 @@ public void Issue2057_DecodeWorks<TPixel>(TestImageProvider<TPixel> provider)
             }
         }
 
+        // https://github.com/SixLabors/ImageSharp/issues/2133
+        [Theory]
+        [WithFile(TestImages.Jpeg.Issues.Issue2133DeduceColorSpace, PixelTypes.Rgba32)]
+        public void Issue2133_DeduceColorSpace<TPixel>(TestImageProvider<TPixel> provider)
+            where TPixel : unmanaged, IPixel<TPixel>
+        {
+            using (Image<TPixel> image = provider.GetImage(JpegDecoder))
+            {
+                image.DebugSave(provider);
+                image.CompareToOriginal(provider);
+            }
+        }
+
         // DEBUG ONLY!
         // The PDF.js output should be saved by "tests\ImageSharp.Tests\Formats\Jpg\pdfjs\jpeg-converter.htm"
         // into "\tests\Images\ActualOutput\JpegDecoderTests\"

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

@@ -265,6 +265,7 @@ public static class Issues
                 public const string Issue2057App1Parsing = "Jpg/issues/Issue2057-App1Parsing.jpg";
                 public const string ExifNullArrayTag = "Jpg/issues/issue-2056-exif-null-array.jpg";
                 public const string ValidExifArgumentNullExceptionOnEncode = "Jpg/issues/Issue2087-exif-null-reference-on-encode.jpg";
+                public const string Issue2133DeduceColorSpace = "Jpg/issues/Issue2133.jpg";
 
                 public static class Fuzz
                 {
@@ -631,6 +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