Merge branch 'main' into js/encoder-normalization

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

@@ -22,7 +22,7 @@ internal class CieLabTiffColor<TPixel> : TiffBaseColorDecoder<TPixel>
     /// <inheritdoc/>
     public override void Decode(ReadOnlySpan<byte> data, Buffer2D<TPixel> pixels, int left, int top, int width, int height)
     {
-        var color = default(TPixel);
+        TPixel color = default;
         int offset = 0;
         for (int y = top; y < top + height; y++)
         {
@@ -31,8 +31,8 @@ internal class CieLabTiffColor<TPixel> : TiffBaseColorDecoder<TPixel>
             for (int x = 0; x < pixelRow.Length; x++)
             {
                 float l = (data[offset] & 0xFF) * 100f * Inv255;
-                var lab = new CieLab(l, (sbyte)data[offset + 1], (sbyte)data[offset + 2]);
+                CieLab lab = new(l, (sbyte)data[offset + 1], (sbyte)data[offset + 2]);
-                var rgb = ColorSpaceConverter.ToRgb(lab);
+                Rgb rgb = ColorSpaceConverter.ToRgb(lab);
 
                 color.FromVector4(new Vector4(rgb.R, rgb.G, rgb.B, 1.0f));
                 pixelRow[x] = color;

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

@@ -0,0 +1,37 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+using System.Numerics;
+using SixLabors.ImageSharp.ColorSpaces;
+using SixLabors.ImageSharp.ColorSpaces.Conversion;
+using SixLabors.ImageSharp.Memory;
+using SixLabors.ImageSharp.PixelFormats;
+
+namespace SixLabors.ImageSharp.Formats.Tiff.PhotometricInterpretation;
+
+internal class CmykTiffColor<TPixel> : TiffBaseColorDecoder<TPixel>
+    where TPixel : unmanaged, IPixel<TPixel>
+{
+    private const float Inv255 = 1 / 255.0f;
+
+    /// <inheritdoc/>
+    public override void Decode(ReadOnlySpan<byte> data, Buffer2D<TPixel> pixels, int left, int top, int width, int height)
+    {
+        TPixel color = default;
+        int offset = 0;
+        for (int y = top; y < top + height; y++)
+        {
+            Span<TPixel> pixelRow = pixels.DangerousGetRowSpan(y).Slice(left, width);
+            for (int x = 0; x < pixelRow.Length; x++)
+            {
+                Cmyk cmyk = new(data[offset] * Inv255, data[offset + 1] * Inv255, data[offset + 2] * Inv255, data[offset + 3] * Inv255);
+                Rgb rgb = ColorSpaceConverter.ToRgb(in cmyk);
+
+                color.FromVector4(new Vector4(rgb.R, rgb.G, rgb.B, 1.0f));
+                pixelRow[x] = color;
+
+                offset += 4;
+            }
+        }
+    }
+}

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

@@ -402,6 +402,16 @@ internal static class TiffColorDecoderFactory<TPixel>
                     "bitsPerSample");
                 return new CieLabTiffColor<TPixel>();
 
+            case TiffColorType.Cmyk:
+                DebugGuard.IsTrue(
+                    bitsPerSample.Channels == 4
+                    && bitsPerSample.Channel3 == 8
+                    && bitsPerSample.Channel2 == 8
+                    && bitsPerSample.Channel1 == 8
+                    && bitsPerSample.Channel0 == 8,
+                    "bitsPerSample");
+                return new CmykTiffColor<TPixel>();
+
             default:
                 throw TiffThrowHelper.InvalidColorType(colorType.ToString());
         }

src/ImageSharp/Formats/Tiff/PhotometricInterpretation/TiffColorType.cs

@@ -287,4 +287,9 @@ internal enum TiffColorType
     /// The pixels are stored in CieLab format as planar.
     /// </summary>
     CieLabPlanar,
+
+    /// <summary>
+    /// The pixels are stored as CMYK.
+    /// </summary>
+    Cmyk,
 }

src/ImageSharp/Formats/Tiff/README.md

@@ -54,7 +54,7 @@
 |Rgb (Planar)               |       |   Y   | General implementation only.              |
 |PaletteColor               |   Y   |   Y   | General implementation only.              |
 |TransparencyMask           |       |       |                                           |
-|Separated (TIFF Extension) |       |       |                                           |
+|Separated (TIFF Extension) |       |   Y   |                                           |
 |YCbCr (TIFF Extension)     |       |   Y   |                                           |
 |CieLab (TIFF Extension)    |       |   Y   |                                           |
 |IccLab (TechNote 1)        |       |       |                                           |

src/ImageSharp/Formats/Tiff/TiffDecoderOptionsParser.cs

@@ -413,6 +413,23 @@ internal static class TiffDecoderOptionsParser
                 break;
             }
 
+            case TiffPhotometricInterpretation.Separated:
+            {
+                if (options.BitsPerSample.Channels != 4)
+                {
+                    TiffThrowHelper.ThrowNotSupported("The number of samples in the TIFF BitsPerSample entry is not supported for CMYK images.");
+                }
+
+                ushort bitsPerChannel = options.BitsPerSample.Channel0;
+                if (bitsPerChannel != 8)
+                {
+                    TiffThrowHelper.ThrowNotSupported("Only 8 bits per channel is supported for CMYK images.");
+                }
+
+                options.ColorType = TiffColorType.Cmyk;
+                break;
+            }
+
             default:
             {
                 TiffThrowHelper.ThrowNotSupported($"The specified TIFF photometric interpretation is not supported: {options.PhotometricInterpretation}");

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

@@ -330,6 +330,18 @@ public class TiffDecoderTests : TiffDecoderBaseTester
         image.CompareToReferenceOutput(ImageComparer.Exact, provider);
     }
 
+    [Theory]
+    [WithFile(Cmyk, PixelTypes.Rgba32)]
+    public void TiffDecoder_CanDecode_Cmyk<TPixel>(TestImageProvider<TPixel> provider)
+        where TPixel : unmanaged, IPixel<TPixel>
+    {
+        // Note: The image from MagickReferenceDecoder does not look right, maybe we are doing something wrong
+        // converting the pixel data from Magick.NET to our format with CMYK?
+        using Image<TPixel> image = provider.GetImage();
+        image.DebugSave(provider);
+        image.CompareToReferenceOutput(ImageComparer.Exact, provider);
+    }
+
     [Theory]
     [WithFile(FlowerRgb101010Contiguous, PixelTypes.Rgba32)]
     [WithFile(FlowerRgb101010Planar, PixelTypes.Rgba32)]

tests/ImageSharp.Tests/TestImages.cs

@@ -936,6 +936,8 @@ public static class TestImages
         public const string CieLabPlanar = "Tiff/CieLabPlanar.tiff";
         public const string CieLabLzwPredictor = "Tiff/CieLab_lzwcompressed_predictor.tiff";
 
+        public const string Cmyk = "Tiff/Cmyk.tiff";
+
         public const string Issues1716Rgb161616BitLittleEndian = "Tiff/Issues/Issue1716.tiff";
         public const string Issues1891 = "Tiff/Issues/Issue1891.tiff";
         public const string Issues2123 = "Tiff/Issues/Issue2123.tiff";

tests/Images/External/ReferenceOutput/TiffDecoderTests/TiffDecoder_CanDecode_Cmyk_Rgba32_Cmyk.png

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:db076491d7afc78cb5de99cb1e7a9c53f891157bf064994c60d453aec75b9c90
+size 512

tests/Images/Input/Tiff/Cmyk.tiff

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:16a73f25e9c2bc6e2e51bd7399d2193bc5d5731f45cfd75147c19746deecf039
+size 40278