Throw NotSupported exception when luma and chroma subsampling is not equal

src/ImageSharp/Formats/Tiff/PhotometricInterpretation/YCbCrTiffColor{TPixel}.cs

@@ -12,37 +12,7 @@ namespace SixLabors.ImageSharp.Formats.Tiff.PhotometricInterpretation
     {
         private readonly YCbCrConverter converter;
 
-        private static readonly Rational[] DefaultLuma =
-        {
-            new Rational(299, 1000),
-            new Rational(587, 1000),
-            new Rational(114, 1000)
-        };
-
-        private static readonly Rational[] DefaultReferenceBlackWhite =
-        {
-            new Rational(0, 1), new Rational(255, 1),
-            new Rational(128, 1), new Rational(255, 1),
-            new Rational(128, 1), new Rational(255, 1)
-        };
-
-        public YCbCrTiffColor(Rational[] referenceBlackAndWhite, Rational[] coefficients)
-        {
-            referenceBlackAndWhite ??= DefaultReferenceBlackWhite;
-            coefficients ??= DefaultLuma;
-
-            if (referenceBlackAndWhite.Length != 6)
-            {
-                TiffThrowHelper.ThrowImageFormatException("reference black and white array should have 6 entry's");
-            }
-
-            if (coefficients.Length != 3)
-            {
-                TiffThrowHelper.ThrowImageFormatException("luma coefficients array should have 6 entry's");
-            }
-
-            this.converter = new YCbCrConverter(referenceBlackAndWhite, coefficients);
-        }
+        public YCbCrTiffColor(Rational[] referenceBlackAndWhite, Rational[] coefficients) => this.converter = new YCbCrConverter(referenceBlackAndWhite, coefficients);
 
         /// <inheritdoc/>
         public override void Decode(ReadOnlySpan<byte> data, Buffer2D<TPixel> pixels, int left, int top, int width, int height)

src/ImageSharp/Formats/Tiff/TiffDecoderOptionsParser.cs

@@ -57,6 +57,12 @@ namespace SixLabors.ImageSharp.Formats.Tiff
                 }
             }
 
+            ushort[] ycbcrSubSampling = exifProfile.GetValue(ExifTag.YCbCrSubsampling)?.Value;
+            if (ycbcrSubSampling != null && ycbcrSubSampling[0] != ycbcrSubSampling[1])
+            {
+                TiffThrowHelper.ThrowNotSupported("ImageSharp only supports YCbCr images with equal luma and chroma samples.");
+            }
+
             if (exifProfile.GetValue(ExifTag.StripRowCounts)?.Value != null)
             {
                 TiffThrowHelper.ThrowNotSupported("Variable-sized strips are not supported.");
@@ -274,6 +280,12 @@ namespace SixLabors.ImageSharp.Formats.Tiff
                         TiffThrowHelper.ThrowNotSupported("The number of samples in the TIFF BitsPerSample entry is not supported.");
                     }
 
+                    ushort bitsPerChannel = options.BitsPerSample.Channel0;
+                    if (bitsPerChannel != 8)
+                    {
+                        TiffThrowHelper.ThrowNotSupported("Only 8 bits per channel is supported for YCbCr images.");
+                    }
+
                     options.ColorType = options.PlanarConfiguration == TiffPlanarConfiguration.Chunky ? TiffColorType.YCbCr : TiffColorType.YCbCrPlanar;
 
                     break;

tests/ImageSharp.Tests/Formats/Tiff/TiffDecoderTests.cs

@@ -160,6 +160,7 @@ namespace SixLabors.ImageSharp.Tests.Formats.Tiff
 
         [Theory]
         [WithFile(FlowerYCbCr888Contiguous, PixelTypes.Rgba32)]
+        [WithFile(FlowerYCbCr888Planar, PixelTypes.Rgba32)]
         public void TiffDecoder_CanDecode_YCbCr_24Bit<TPixel>(TestImageProvider<TPixel> provider)
             where TPixel : unmanaged, IPixel<TPixel> => TestTiffDecoder(provider);
 

tests/ImageSharp.Tests/TestImages.cs

@@ -575,8 +575,8 @@ namespace SixLabors.ImageSharp.Tests
             public const string FlowerRgb888Contiguous = "Tiff/flower-rgb-contig-08.tiff";
             public const string FlowerRgb888Planar6Strips = "Tiff/flower-rgb-planar-08-6strips.tiff";
             public const string FlowerRgb888Planar15Strips = "Tiff/flower-rgb-planar-08-15strips.tiff";
-            public const string FlowerYCbCr888Contiguous = "Tiff/flower_ycbcr_contig-08.tiff";
-            public const string FlowerYCbCr888Planar = "Tiff/flower_ycbcr_planar-08.tiff";
+            public const string FlowerYCbCr888Contiguous = "Tiff/flower-ycbcr-contig-08.tiff";
+            public const string FlowerYCbCr888Planar = "Tiff/flower-ycbcr-planar-08.tiff";
             public const string FlowerRgb444Contiguous = "Tiff/flower-rgb-contig-04.tiff";
             public const string FlowerRgb444Planar = "Tiff/flower-rgb-planar-04.tiff";
             public const string FlowerRgb222Contiguous = "Tiff/flower-rgb-contig-02.tiff";