Add support for decoding tiff's with float pixel data

src/ImageSharp/Formats/Tiff/PhotometricInterpretation/BlackIsZero32FloatTiffColor{TPixel}.cs

@@ -0,0 +1,69 @@
+// 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 'BlackIsZero' photometric interpretation for 32-bit float grayscale images.
+    /// </summary>
+    internal class BlackIsZero32FloatTiffColor<TPixel> : TiffBaseColorDecoder<TPixel>
+        where TPixel : unmanaged, IPixel<TPixel>
+    {
+        private readonly bool isBigEndian;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="BlackIsZero32FloatTiffColor{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 BlackIsZero32FloatTiffColor(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);
+            byte[] buffer = new byte[4];
+
+            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++)
+                    {
+                        data.Slice(offset, 4).CopyTo(buffer);
+                        Array.Reverse(buffer);
+                        float intensity = BitConverter.ToSingle(buffer, 0);
+                        offset += 4;
+
+                        var colorVector = new Vector4(intensity, intensity, intensity, 1.0f);
+                        color.FromVector4(colorVector);
+                        pixelRow[x] = color;
+                    }
+                }
+                else
+                {
+                    for (int x = 0; x < pixelRow.Length; x++)
+                    {
+                        data.Slice(offset, 4).CopyTo(buffer);
+                        float intensity = BitConverter.ToSingle(buffer, 0);
+                        offset += 4;
+
+                        var colorVector = new Vector4(intensity, intensity, intensity, 1.0f);
+                        color.FromVector4(colorVector);
+                        pixelRow[x] = color;
+                    }
+                }
+            }
+        }
+    }
+}

src/ImageSharp/Formats/Tiff/PhotometricInterpretation/BlackIsZero32TiffColor{TPixel}.cs

@@ -2,7 +2,6 @@
 // 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;

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

@@ -0,0 +1,88 @@
+// 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);
+                        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

@@ -47,6 +47,11 @@ public static TiffBaseColorDecoder<TPixel> Create(Configuration configuration, T
                     DebugGuard.IsTrue(colorMap == null, "colorMap");
                     return new WhiteIsZero32TiffColor<TPixel>(byteOrder == ByteOrder.BigEndian);
 
+                case TiffColorType.WhiteIsZero32Float:
+                    DebugGuard.IsTrue(bitsPerSample.Channels == 1 && bitsPerSample.Channel0 == 32, "bitsPerSample");
+                    DebugGuard.IsTrue(colorMap == null, "colorMap");
+                    return new WhiteIsZero32FloatTiffColor<TPixel>(byteOrder == ByteOrder.BigEndian);
+
                 case TiffColorType.BlackIsZero:
                     DebugGuard.IsTrue(bitsPerSample.Channels == 1, "bitsPerSample");
                     DebugGuard.IsTrue(colorMap == null, "colorMap");
@@ -82,6 +87,11 @@ public static TiffBaseColorDecoder<TPixel> Create(Configuration configuration, T
                     DebugGuard.IsTrue(colorMap == null, "colorMap");
                     return new BlackIsZero32TiffColor<TPixel>(byteOrder == ByteOrder.BigEndian);
 
+                case TiffColorType.BlackIsZero32Float:
+                    DebugGuard.IsTrue(bitsPerSample.Channels == 1 && bitsPerSample.Channel0 == 32, "bitsPerSample");
+                    DebugGuard.IsTrue(colorMap == null, "colorMap");
+                    return new BlackIsZero32FloatTiffColor<TPixel>(byteOrder == ByteOrder.BigEndian);
+
                 case TiffColorType.Rgb:
                     DebugGuard.IsTrue(colorMap == null, "colorMap");
                     return new RgbTiffColor<TPixel>(bitsPerSample);
@@ -176,6 +186,16 @@ public static TiffBaseColorDecoder<TPixel> Create(Configuration configuration, T
                     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

@@ -43,6 +43,11 @@ internal enum TiffColorType
         /// </summary>
         BlackIsZero32,
 
+        /// <summary>
+        /// Grayscale: 0 is imaged as black. The maximum value is imaged as white. Pixel data is 32-bit float.
+        /// </summary>
+        BlackIsZero32Float,
+
         /// <summary>
         /// Grayscale: 0 is imaged as white. The maximum value is imaged as black.
         /// </summary>
@@ -78,6 +83,11 @@ internal enum TiffColorType
         /// </summary>
         WhiteIsZero32,
 
+        /// <summary>
+        /// Grayscale: 0 is imaged as black. The maximum value is imaged as white. Pixel data is 32-bit float.
+        /// </summary>
+        WhiteIsZero32Float,
+
         /// <summary>
         /// Palette-color.
         /// </summary>
@@ -133,6 +143,11 @@ internal enum TiffColorType
         /// </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/PhotometricInterpretation/WhiteIsZero24TiffColor{TPixel}.cs

@@ -31,6 +31,7 @@ public override void Decode(ReadOnlySpan<byte> data, Buffer2D<TPixel> pixels, in
             color.FromVector4(TiffUtils.Vector4Default);
             byte[] buffer = new byte[4];
             int bufferStartIdx = this.isBigEndian ? 1 : 0;
+            const uint maxValue = 0xFFFFFF;
 
             Span<byte> bufferSpan = buffer.AsSpan(bufferStartIdx);
             int offset = 0;
@@ -42,7 +43,7 @@ public override void Decode(ReadOnlySpan<byte> data, Buffer2D<TPixel> pixels, in
                     for (int x = 0; x < pixelRow.Length; x++)
                     {
                         data.Slice(offset, 3).CopyTo(bufferSpan);
-                        ulong intensity = TiffUtils.ConvertToUIntBigEndian(buffer);
+                        ulong intensity = maxValue - TiffUtils.ConvertToUIntBigEndian(buffer);
                         offset += 3;
 
                         pixelRow[x] = TiffUtils.ColorScaleTo24Bit(intensity, color);
@@ -53,7 +54,7 @@ public override void Decode(ReadOnlySpan<byte> data, Buffer2D<TPixel> pixels, in
                     for (int x = 0; x < pixelRow.Length; x++)
                     {
                         data.Slice(offset, 3).CopyTo(bufferSpan);
-                        ulong intensity = TiffUtils.ConvertToUIntLittleEndian(buffer);
+                        ulong intensity = maxValue - TiffUtils.ConvertToUIntLittleEndian(buffer);
                         offset += 3;
 
                         pixelRow[x] = TiffUtils.ColorScaleTo24Bit(intensity, color);

src/ImageSharp/Formats/Tiff/PhotometricInterpretation/WhiteIsZero32FloatTiffColor{TPixel}.cs

@@ -0,0 +1,69 @@
+// 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 'WhiteIsZero' photometric interpretation for 32-bit float grayscale images.
+    /// </summary>
+    internal class WhiteIsZero32FloatTiffColor<TPixel> : TiffBaseColorDecoder<TPixel>
+        where TPixel : unmanaged, IPixel<TPixel>
+    {
+        private readonly bool isBigEndian;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="WhiteIsZero32FloatTiffColor{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 WhiteIsZero32FloatTiffColor(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);
+            byte[] buffer = new byte[4];
+
+            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++)
+                    {
+                        data.Slice(offset, 4).CopyTo(buffer);
+                        Array.Reverse(buffer);
+                        float intensity = 1.0f - BitConverter.ToSingle(buffer, 0);
+                        offset += 4;
+
+                        var colorVector = new Vector4(intensity, intensity, intensity, 1.0f);
+                        color.FromVector4(colorVector);
+                        pixelRow[x] = color;
+                    }
+                }
+                else
+                {
+                    for (int x = 0; x < pixelRow.Length; x++)
+                    {
+                        data.Slice(offset, 4).CopyTo(buffer);
+                        float intensity = 1.0f - BitConverter.ToSingle(buffer, 0);
+                        offset += 4;
+
+                        var colorVector = new Vector4(intensity, intensity, intensity, 1.0f);
+                        color.FromVector4(colorVector);
+                        pixelRow[x] = color;
+                    }
+                }
+            }
+        }
+    }
+}

src/ImageSharp/Formats/Tiff/PhotometricInterpretation/WhiteIsZero32TiffColor{TPixel}.cs

@@ -29,6 +29,7 @@ public override void Decode(ReadOnlySpan<byte> data, Buffer2D<TPixel> pixels, in
             // we define our own defaults as a workaround. See: https://github.com/dotnet/runtime/issues/55623
             var color = default(TPixel);
             color.FromVector4(TiffUtils.Vector4Default);
+            const uint maxValue = 0xFFFFFFFF;
 
             int offset = 0;
             for (int y = top; y < top + height; y++)
@@ -38,7 +39,7 @@ public override void Decode(ReadOnlySpan<byte> data, Buffer2D<TPixel> pixels, in
                 {
                     for (int x = 0; x < pixelRow.Length; x++)
                     {
-                        ulong intensity = TiffUtils.ConvertToUIntBigEndian(data.Slice(offset, 4));
+                        ulong intensity = maxValue - TiffUtils.ConvertToUIntBigEndian(data.Slice(offset, 4));
                         offset += 4;
 
                         pixelRow[x] = TiffUtils.ColorScaleTo32Bit(intensity, color);
@@ -48,7 +49,7 @@ public override void Decode(ReadOnlySpan<byte> data, Buffer2D<TPixel> pixels, in
                 {
                     for (int x = 0; x < pixelRow.Length; x++)
                     {
-                        ulong intensity = TiffUtils.ConvertToUIntLittleEndian(data.Slice(offset, 4));
+                        ulong intensity = maxValue - TiffUtils.ConvertToUIntLittleEndian(data.Slice(offset, 4));
                         offset += 4;
 
                         pixelRow[x] = TiffUtils.ColorScaleTo32Bit(intensity, color);

src/ImageSharp/Formats/Tiff/PhotometricInterpretation/WhiteIsZero8TiffColor{TPixel}.cs

@@ -27,7 +27,7 @@ public override void Decode(ReadOnlySpan<byte> data, Buffer2D<TPixel> pixels, in
                 Span<TPixel> pixelRow = pixels.GetRowSpan(y).Slice(left, width);
                 for (int x = 0; x < pixelRow.Length; x++)
                 {
-                    byte intensity = (byte)(255 - data[offset++]);
+                    byte intensity = (byte)(byte.MaxValue - data[offset++]);
                     pixelRow[x] = TiffUtils.ColorFromL8(l8, intensity, color);
                 }
             }

src/ImageSharp/Formats/Tiff/TiffDecoderCore.cs

@@ -100,6 +100,11 @@ public TiffDecoderCore(Configuration configuration, ITiffDecoderOptions options)
         /// </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>