Add support for decoding tiff's with 32bit float rgb pixel data

src/ImageSharp/Formats/Tiff/PhotometricInterpretation/RgbFloat323232TiffColor{TPixel}.cs

@@ -0,0 +1,89 @@
+// Copyright (c) Six Labors.
+// Licensed under the Apache License, Version 2.0.
+
+using System;
+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 32 bits for each channel.
+    /// </summary>
+    internal class RgbFloat323232TiffColor<TPixel> : TiffBaseColorDecoder<TPixel>
+        where TPixel : unmanaged, IPixel<TPixel>
+    {
+        private readonly bool isBigEndian;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="RgbFloat323232TiffColor{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 RgbFloat323232TiffColor(bool isBigEndian) => this.isBigEndian = isBigEndian;
+
+        /// <inheritdoc/>
+        public override void Decode(ReadOnlySpan<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);
+            int offset = 0;
+            byte[] buffer = new byte[4];
+
+            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++)
+                    {
+                        data.Slice(offset, 4).CopyTo(buffer);
+                        Array.Reverse(buffer);
+                        float r = BitConverter.ToSingle(buffer, 0);
+                        offset += 4;
+
+                        data.Slice(offset, 4).CopyTo(buffer);
+                        Array.Reverse(buffer);
+                        float g = BitConverter.ToSingle(buffer, 0);
+                        offset += 4;
+
+                        data.Slice(offset, 4).CopyTo(buffer);
+                        Array.Reverse(buffer);
+                        float b = BitConverter.ToSingle(buffer, 0);
+                        offset += 4;
+
+                        var colorVector = new Vector4(r, g, b, 1.0f);
+                        Array.Reverse(buffer);
+                        color.FromVector4(colorVector);
+                        pixelRow[x] = color;
+                    }
+                }
+                else
+                {
+                    for (int x = 0; x < pixelRow.Length; x++)
+                    {
+                        data.Slice(offset, 4).CopyTo(buffer);
+                        float r = BitConverter.ToSingle(buffer, 0);
+                        offset += 4;
+
+                        data.Slice(offset, 4).CopyTo(buffer);
+                        float g = BitConverter.ToSingle(buffer, 0);
+                        offset += 4;
+
+                        data.Slice(offset, 4).CopyTo(buffer);
+                        float b = BitConverter.ToSingle(buffer, 0);
+                        offset += 4;
+
+                        var colorVector = new Vector4(r, g, b, 1.0f);
+                        color.FromVector4(colorVector);
+                        pixelRow[x] = color;
+                    }
+                }
+            }
+        }
+    }
+}

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

@@ -176,6 +176,16 @@ namespace SixLabors.ImageSharp.Formats.Tiff.PhotometricInterpretation
                     DebugGuard.IsTrue(colorMap == null, "colorMap");
                     return new Rgb323232TiffColor<TPixel>(isBigEndian: byteOrder == ByteOrder.BigEndian);
 
+                case TiffColorType.RgbFloat323232:
+                    DebugGuard.IsTrue(
+                        bitsPerSample.Channels == 3
+                        && bitsPerSample.Channel2 == 32
+                        && bitsPerSample.Channel1 == 32
+                        && bitsPerSample.Channel0 == 32,
+                        "bitsPerSample");
+                    DebugGuard.IsTrue(colorMap == null, "colorMap");
+                    return new RgbFloat323232TiffColor<TPixel>(isBigEndian: byteOrder == ByteOrder.BigEndian);
+
                 case TiffColorType.PaletteColor:
                     DebugGuard.NotNull(colorMap, "colorMap");
                     return new PaletteTiffColor<TPixel>(bitsPerSample, colorMap);

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

@@ -133,6 +133,11 @@ namespace SixLabors.ImageSharp.Formats.Tiff.PhotometricInterpretation
         /// </summary>
         Rgb323232,
 
+        /// <summary>
+        /// RGB color image with 32 bits floats for each channel.
+        /// </summary>
+        RgbFloat323232,
+
         /// <summary>
         /// RGB Full Color. Planar configuration of data. 8 Bit per color channel.
         /// </summary>

src/ImageSharp/Formats/Tiff/TiffDecoderCore.cs

@@ -95,6 +95,11 @@ namespace SixLabors.ImageSharp.Formats.Tiff
         /// </summary>
         public TiffPhotometricInterpretation PhotometricInterpretation { get; set; }
 
+        /// <summary>
+        /// Gets or sets the sample format.
+        /// </summary>
+        public TiffSampleFormat SampleFormat { get; set; }
+
         /// <summary>
         /// Gets or sets the horizontal predictor.
         /// </summary>

src/ImageSharp/Formats/Tiff/TiffDecoderOptionsParser.cs

@@ -45,14 +45,16 @@ namespace SixLabors.ImageSharp.Formats.Tiff
                 TiffThrowHelper.ThrowNotSupported("TIFF images with FloatingPoint horizontal predictor are not supported.");
             }
 
-            TiffSampleFormat[] sampleFormat = exifProfile.GetValue(ExifTag.SampleFormat)?.Value?.Select(a => (TiffSampleFormat)a).ToArray();
-            if (sampleFormat != null)
+            TiffSampleFormat[] sampleFormats = exifProfile.GetValue(ExifTag.SampleFormat)?.Value?.Select(a => (TiffSampleFormat)a).ToArray();
+            TiffSampleFormat? sampleFormat = null;
+            if (sampleFormats != null)
             {
-                foreach (TiffSampleFormat format in sampleFormat)
+                sampleFormat = sampleFormats[0];
+                foreach (TiffSampleFormat format in sampleFormats)
                 {
-                    if (format != TiffSampleFormat.UnsignedInteger)
+                    if (format != TiffSampleFormat.UnsignedInteger && format != TiffSampleFormat.Float)
                     {
-                        TiffThrowHelper.ThrowNotSupported("ImageSharp only supports the UnsignedInteger SampleFormat.");
+                        TiffThrowHelper.ThrowNotSupported("ImageSharp only supports the UnsignedInteger and Float SampleFormat.");
                     }
                 }
             }
@@ -67,6 +69,7 @@ namespace SixLabors.ImageSharp.Formats.Tiff
             options.PlanarConfiguration = (TiffPlanarConfiguration?)exifProfile.GetValue(ExifTag.PlanarConfiguration)?.Value ?? DefaultPlanarConfiguration;
             options.Predictor = frameMetadata.Predictor ?? TiffPredictor.None;
             options.PhotometricInterpretation = frameMetadata.PhotometricInterpretation ?? TiffPhotometricInterpretation.Rgb;
+            options.SampleFormat = sampleFormat ?? TiffSampleFormat.UnsignedInteger;
             options.BitsPerPixel = frameMetadata.BitsPerPixel != null ? (int)frameMetadata.BitsPerPixel.Value : (int)TiffBitsPerPixel.Bit24;
             options.BitsPerSample = frameMetadata.BitsPerSample ?? new TiffBitsPerSample(0, 0, 0);
 
@@ -231,6 +234,12 @@ namespace SixLabors.ImageSharp.Formats.Tiff
                         TiffThrowHelper.ThrowNotSupported("Only BitsPerSample with equal bits per channel are supported.");
                     }
 
+                    if (options.SampleFormat == TiffSampleFormat.Float)
+                    {
+                        options.ColorType = TiffColorType.RgbFloat323232;
+                        return;
+                    }
+
                     if (options.PlanarConfiguration == TiffPlanarConfiguration.Chunky)
                     {
                         ushort bitsPerChannel = options.BitsPerSample.Channel0;

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

@@ -237,6 +237,17 @@ namespace SixLabors.ImageSharp.Tests.Formats.Tiff
             image.DebugSave(provider);
         }
 
+        [Theory]
+        [WithFile(FlowerRgbFloat323232, PixelTypes.Rgba32)]
+        [WithFile(FlowerRgbFloat323232LittleEndian, PixelTypes.Rgba32)]
+        public void TiffDecoder_CanDecode_Float_96Bit<TPixel>(TestImageProvider<TPixel> provider)
+            where TPixel : unmanaged, IPixel<TPixel>
+        {
+            // Note: because the MagickReferenceDecoder fails to load the image, we only debug save them.
+            using Image<TPixel> image = provider.GetImage();
+            image.DebugSave(provider);
+        }
+
         [Theory]
         [WithFile(GrayscaleDeflateMultistrip, PixelTypes.Rgba32)]
         [WithFile(RgbDeflateMultistrip, PixelTypes.Rgba32)]

tests/ImageSharp.Tests/TestImages.cs

@@ -563,6 +563,8 @@ 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 FlowerRgbFloat323232 = "Tiff/flower-rgb-float32_msb.tiff";
+            public const string FlowerRgbFloat323232LittleEndian = "Tiff/flower-rgb-float32_lsb.tiff";
             public const string FlowerRgb323232Contiguous = "Tiff/flower-rgb-contig-32.tiff";
             public const string FlowerRgb323232ContiguousLittleEndian = "Tiff/flower-rgb-contig-32_lsb.tiff";
             public const string FlowerRgb323232Planar = "Tiff/flower-rgb-planar-32.tiff";

tests/Images/Input/Tiff/flower-rgb-float32_lsb.tiff

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:a1f889baa6f3bb99f15609848cdd47d548d3e2ed1b7b558d428550dfa3bd4bf9
+size 38050

tests/Images/Input/Tiff/flower-rgb-float32_msb.tiff

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:2c02be5dff2bcd5d60afbf379ba9095b0c8fd3a7a0063f684ac9ac9119f967a5
+size 38050