Tiif decoding fix

src/ImageSharp/Formats/Jpeg/JpegDecoderCore.cs

@@ -503,9 +503,9 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
         }
 
         /// <summary>
-        /// Returns the correct colorspace based on the image component count and the jpeg frame component id's.
+        /// Returns encoded colorspace based on the adobe APP14 marker.
         /// </summary>
-        /// <param name="componentCount">The number of components.</param>
+        /// <param name="componentCount">Number of components.</param>
         /// <param name="adobeMarker">Parsed adobe APP14 marker.</param>
         /// <returns>The <see cref="JpegColorSpace"/></returns>
         internal static JpegColorSpace DeduceJpegColorSpace(byte componentCount, ref AdobeMarker adobeMarker)
@@ -534,6 +534,15 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
             return default;
         }
 
+        /// <summary>
+        /// Returns encoded colorspace based on the component count and component ids.
+        /// </summary>
+        /// <remarks>
+        /// Must take into account atleast RGB component identifiers i.e. [82, 71, 66]
+        /// as TIFF images with jpeg encoding don't have APP14 marker.
+        /// </remarks>
+        /// <param name="componentCount">Number of components.</param>
+        /// <returns>The <see cref="JpegColorSpace"/></returns>
         internal static JpegColorSpace DeduceJpegColorSpace(byte componentCount)
         {
             if (componentCount == 1)
@@ -1216,7 +1225,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
             int maxH = 0;
             int maxV = 0;
             int index = 0;
-            for (int i = 0; i < componentCount; i++)
+            for (int i = 0; i < this.Frame.Components.Length; i++)
             {
                 // 1 byte: component identifier
                 byte componentId = this.temp[index];

src/ImageSharp/Formats/Tiff/Compression/Decompressors/JpegTiffCompression.cs

@@ -59,7 +59,8 @@ namespace SixLabors.ImageSharp.Formats.Tiff.Compression.Decompressors
                     case TiffPhotometricInterpretation.BlackIsZero:
                     case TiffPhotometricInterpretation.WhiteIsZero:
                     {
-                        using SpectralConverter<L8> spectralConverterGray = new GrayJpegSpectralConverter<L8>(this.configuration);
+                        using SpectralConverter<L8> spectralConverterGray =
+                            new GrayJpegSpectralConverter<L8>(this.configuration);
                         var scanDecoderGray = new HuffmanScanDecoder(stream, spectralConverterGray, CancellationToken.None);
                         jpegDecoder.LoadTables(this.jpegTables, scanDecoderGray);
                         jpegDecoder.ParseStream(stream, spectralConverterGray, CancellationToken.None);
@@ -73,9 +74,8 @@ namespace SixLabors.ImageSharp.Formats.Tiff.Compression.Decompressors
                     case TiffPhotometricInterpretation.YCbCr:
                     case TiffPhotometricInterpretation.Rgb:
                     {
-                        // The jpeg data should treated as RGB color space. If the PhotometricInterpretation is YCbCr,
+                        using SpectralConverter<Rgb24> spectralConverter =
-                        // the conversion to RGB will be handled in the next step by the YCbCr color decoder.
+                            new TiffJpegSpectralConverter<Rgb24>(this.configuration, this.photometricInterpretation);
-                        using SpectralConverter<Rgb24> spectralConverter = new RgbJpegSpectralConverter<Rgb24>(this.configuration);
                         var scanDecoder = new HuffmanScanDecoder(stream, spectralConverter, CancellationToken.None);
                         jpegDecoder.LoadTables(this.jpegTables, scanDecoder);
                         jpegDecoder.ParseStream(stream, spectralConverter, CancellationToken.None);

src/ImageSharp/Formats/Tiff/Compression/Decompressors/RgbJpegSpectralConverter.cs

@@ -1,32 +0,0 @@
-// Copyright (c) Six Labors.
-// Licensed under the Apache License, Version 2.0.
-
-using SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder;
-using SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder.ColorConverters;
-using SixLabors.ImageSharp.PixelFormats;
-
-namespace SixLabors.ImageSharp.Formats.Tiff.Compression.Decompressors
-{
-    /// <summary>
-    /// Spectral converter for TIFF's which use the JPEG compression.
-    /// The compressed jpeg data should be always treated as RGB color space.
-    /// If PhotometricInterpretation indicates the data is YCbCr, the color decoder will handle the conversion.
-    /// </summary>
-    /// <typeparam name="TPixel">The type of the pixel.</typeparam>
-    internal sealed class RgbJpegSpectralConverter<TPixel> : SpectralConverter<TPixel>
-        where TPixel : unmanaged, IPixel<TPixel>
-    {
-        /// <summary>
-        /// Initializes a new instance of the <see cref="RgbJpegSpectralConverter{TPixel}"/> class.
-        /// This Spectral converter will always convert the pixel data to RGB color.
-        /// </summary>
-        /// <param name="configuration">The configuration.</param>
-        public RgbJpegSpectralConverter(Configuration configuration)
-            : base(configuration)
-        {
-        }
-
-        /// <inheritdoc/>
-        protected override JpegColorConverterBase GetColorConverter(JpegFrame frame, IRawJpegData jpegData) => JpegColorConverterBase.GetConverter(JpegColorSpace.RGB, frame.Precision);
-    }
-}

src/ImageSharp/Formats/Tiff/Compression/Decompressors/TiffJpegSpectralConverter{TPixel}.cs

@@ -0,0 +1,50 @@
+// Copyright (c) Six Labors.
+// Licensed under the Apache License, Version 2.0.
+
+using SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder;
+using SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder.ColorConverters;
+using SixLabors.ImageSharp.Formats.Tiff.Constants;
+using SixLabors.ImageSharp.PixelFormats;
+
+namespace SixLabors.ImageSharp.Formats.Tiff.Compression.Decompressors
+{
+    /// <summary>
+    /// Spectral converter for YCbCr TIFF's which use the JPEG compression.
+    /// The jpeg data should be always treated as RGB color space.
+    /// </summary>
+    /// <typeparam name="TPixel">The type of the pixel.</typeparam>
+    internal sealed class TiffJpegSpectralConverter<TPixel> : SpectralConverter<TPixel>
+        where TPixel : unmanaged, IPixel<TPixel>
+    {
+        private readonly TiffPhotometricInterpretation photometricInterpretation;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="TiffJpegSpectralConverter{TPixel}"/> class.
+        /// This Spectral converter will always convert the pixel data to RGB color.
+        /// </summary>
+        /// <param name="configuration">The configuration.</param>
+        /// <param name="photometricInterpretation">Tiff photometric interpretation.</param>
+        public TiffJpegSpectralConverter(Configuration configuration, TiffPhotometricInterpretation photometricInterpretation)
+            : base(configuration)
+            => this.photometricInterpretation = photometricInterpretation;
+
+        /// <inheritdoc/>
+        protected override JpegColorConverterBase GetColorConverter(JpegFrame frame, IRawJpegData jpegData)
+        {
+            JpegColorSpace colorSpace = GetJpegColorSpaceFromPhotometricInterpretation(this.photometricInterpretation);
+            return JpegColorConverterBase.GetConverter(colorSpace, frame.Precision);
+        }
+
+        /// <remarks>
+        /// This converter must be used only for RGB and YCbCr color spaces for performance reasons.
+        /// For grayscale images <see cref="GrayJpegSpectralConverter{TPixel}"/> must be used.
+        /// </remarks>
+        private static JpegColorSpace GetJpegColorSpaceFromPhotometricInterpretation(TiffPhotometricInterpretation interpretation)
+            => interpretation switch
+            {
+                TiffPhotometricInterpretation.Rgb => JpegColorSpace.RGB,
+                TiffPhotometricInterpretation.YCbCr => JpegColorSpace.RGB,
+                _ => throw new InvalidImageContentException($"Invalid tiff photometric interpretation for jpeg encoding: {interpretation}"),
+            };
+    }
+}

tests/ImageSharp.Tests/Formats/Jpg/JpegDecoderTests.Internal.cs

@@ -33,8 +33,8 @@ namespace SixLabors.ImageSharp.Tests.Formats.Jpg
         {
             byte[] adobeMarkerPayload = new byte[] { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, adobeFlag };
             ProfileResolver.AdobeMarker.CopyTo(adobeMarkerPayload);
-
             _ = AdobeMarker.TryParse(adobeMarkerPayload, out AdobeMarker adobeMarker);
+
             JpegColorSpace actualColorSpace = JpegDecoderCore.DeduceJpegColorSpace(componentCount, ref adobeMarker);
 
             Assert.Equal(expectedColorSpace, actualColorSpace);
@@ -46,6 +46,7 @@ namespace SixLabors.ImageSharp.Tests.Formats.Jpg
         public void DeduceJpegColorSpaceAdobeMarker_ShouldThrowOnUnsupportedComponentCount(byte componentCount)
         {
             AdobeMarker adobeMarker = default;
+
             Assert.Throws<NotSupportedException>(() => JpegDecoderCore.DeduceJpegColorSpace(componentCount, ref adobeMarker));
         }