Add support for decoding 24bit per channel color tiff with planar pixel data

src/ImageSharp/Formats/Tiff/PhotometricInterpretation/Rgb16PlanarTiffColor{TPixel}.cs

@@ -10,7 +10,7 @@ using SixLabors.ImageSharp.PixelFormats;
 namespace SixLabors.ImageSharp.Formats.Tiff.PhotometricInterpretation
 {
     /// <summary>
-    /// Implements the 'RGB' photometric interpretation with 'Planar' layout for all 16 bit.
+    /// Implements the 'RGB' photometric interpretation with 'Planar' layout for each color channel with 16 bit.
     /// </summary>
     internal class Rgb16PlanarTiffColor<TPixel> : TiffBasePlanarColorDecoder<TPixel>
         where TPixel : unmanaged, IPixel<TPixel>

src/ImageSharp/Formats/Tiff/PhotometricInterpretation/Rgb24PlanarTiffColor{TPixel}.cs

@@ -0,0 +1,87 @@
+// Copyright (c) Six Labors.
+// Licensed under the Apache License, Version 2.0.
+
+using System;
+using System.Buffers;
+using System.Numerics;
+using SixLabors.ImageSharp.Formats.Tiff.Utils;
+using SixLabors.ImageSharp.Memory;
+using SixLabors.ImageSharp.PixelFormats;
+
+namespace SixLabors.ImageSharp.Formats.Tiff.PhotometricInterpretation
+{
+    /// <summary>
+    /// Implements the 'RGB' photometric interpretation with 'Planar' layout for each color channel with 24 bit.
+    /// </summary>
+    internal class Rgb24PlanarTiffColor<TPixel> : TiffBasePlanarColorDecoder<TPixel>
+        where TPixel : unmanaged, IPixel<TPixel>
+    {
+        private readonly bool isBigEndian;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Rgb24PlanarTiffColor{TPixel}" /> class.
+        /// </summary>
+        /// <param name="isBigEndian">if set to <c>true</c> decodes the pixel data as big endian, otherwise as little endian.</param>
+        public Rgb24PlanarTiffColor(bool isBigEndian) => this.isBigEndian = isBigEndian;
+
+        /// <inheritdoc/>
+        public override void Decode(IMemoryOwner<byte>[] data, Buffer2D<TPixel> pixels, int left, int top, int width, int height)
+        {
+            // Note: due to an issue with netcore 2.1 and default values and unpredictable behavior with those,
+            // we define our own defaults as a workaround. See: https://github.com/dotnet/runtime/issues/55623
+            var color = default(TPixel);
+            color.FromVector4(TiffUtils.Vector4Default);
+            float scale = 1.0f / 0xFFFFFF;
+            byte[] buffer = new byte[4];
+            int bufferStartIdx = this.isBigEndian ? 1 : 0;
+
+            Span<byte> redData = data[0].GetSpan();
+            Span<byte> greenData = data[1].GetSpan();
+            Span<byte> blueData = data[2].GetSpan();
+
+            int offset = 0;
+            for (int y = top; y < top + height; y++)
+            {
+                Span<TPixel> pixelRow = pixels.GetRowSpan(y).Slice(left, width);
+                if (this.isBigEndian)
+                {
+                    for (int x = 0; x < pixelRow.Length; x++)
+                    {
+                        redData.Slice(offset, 3).CopyTo(buffer.AsSpan(bufferStartIdx));
+                        ulong r = TiffUtils.ConvertToUIntBigEndian(buffer);
+                        greenData.Slice(offset, 3).CopyTo(buffer.AsSpan(bufferStartIdx));
+                        ulong g = TiffUtils.ConvertToUIntBigEndian(buffer);
+                        blueData.Slice(offset, 3).CopyTo(buffer.AsSpan(bufferStartIdx));
+                        ulong b = TiffUtils.ConvertToUIntBigEndian(buffer);
+
+                        offset += 3;
+
+                        var colorVector = new Vector4(r * scale, g * scale, b * scale, 1.0f);
+                        color.FromVector4(colorVector);
+
+                        pixelRow[x] = color;
+                    }
+                }
+                else
+                {
+                    for (int x = 0; x < pixelRow.Length; x++)
+                    {
+                        redData.Slice(offset, 3).CopyTo(buffer.AsSpan(bufferStartIdx));
+                        ulong r = TiffUtils.ConvertToUIntLittleEndian(buffer);
+                        greenData.Slice(offset, 3).CopyTo(buffer.AsSpan(bufferStartIdx));
+                        ulong g = TiffUtils.ConvertToUIntLittleEndian(buffer);
+                        blueData.Slice(offset, 3).CopyTo(buffer.AsSpan(bufferStartIdx));
+                        ulong b = TiffUtils.ConvertToUIntLittleEndian(buffer);
+
+                        offset += 3;
+
+                        var colorVector = new Vector4(r * scale, g * scale, b * scale, 1.0f);
+                        color.FromVector4(colorVector);
+
+                        pixelRow[x] = color;
+                    }
+                }
+            }
+        }
+    }
+}

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

@@ -166,6 +166,11 @@ namespace SixLabors.ImageSharp.Formats.Tiff.PhotometricInterpretation
                         return new Rgb16PlanarTiffColor<TPixel>(byteOrder == ByteOrder.BigEndian);
                     }
 
+                    if (bitsPerSample.Channel0 == 24 && bitsPerSample.Channel1 == 24 && bitsPerSample.Channel2 == 24)
+                    {
+                        return new Rgb24PlanarTiffColor<TPixel>(byteOrder == ByteOrder.BigEndian);
+                    }
+
                     return new RgbPlanarTiffColor<TPixel>(bitsPerSample);
 
                 default:

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

@@ -176,6 +176,8 @@ namespace SixLabors.ImageSharp.Tests.Formats.Tiff
         [Theory]
         [WithFile(FlowerRgb242424Contiguous, PixelTypes.Rgba32)]
         [WithFile(FlowerRgb242424ContiguousLittleEndian, PixelTypes.Rgba32)]
+        [WithFile(FlowerRgb242424Planar, PixelTypes.Rgba32)]
+        [WithFile(FlowerRgb242424PlanarLittleEndian, PixelTypes.Rgba32)]
         public void TiffDecoder_CanDecode_72Bit<TPixel>(TestImageProvider<TPixel> provider)
             where TPixel : unmanaged, IPixel<TPixel> => TestTiffDecoder(provider);
 

tests/ImageSharp.Tests/TestImages.cs

@@ -561,6 +561,8 @@ namespace SixLabors.ImageSharp.Tests
             public const string RgbPalette = "Tiff/rgb_palette.tiff";
             public const string Rgb4BitPalette = "Tiff/bike_colorpalette_4bit.tiff";
             public const string RgbPaletteDeflate = "Tiff/rgb_palette_deflate.tiff";
+            public const string FlowerRgb242424Planar = "Tiff/flower-rgb-planar-24.tiff";
+            public const string FlowerRgb242424PlanarLittleEndian = "Tiff/flower-rgb-planar-24_lsb.tiff";
             public const string FlowerRgb242424Contiguous = "Tiff/flower-rgb-contig-24.tiff";
             public const string FlowerRgb242424ContiguousLittleEndian = "Tiff/flower-rgb-contig-24_lsb.tiff";
             public const string FlowerRgb161616Contiguous = "Tiff/flower-rgb-contig-16.tiff";

tests/Images/Input/Tiff/flower-rgb-planar-24.tiff

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:752452ac51ad1e836fb81267ab708ff81cf81a4c7e00daeed703f67782b563ec
+size 28586

tests/Images/Input/Tiff/flower-rgb-planar-24_lsb.tiff

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:72f27af4fe177ebe47bef2af64723497d5a5f44808424bedfc2012fe4e3fc34e
+size 28586