Add support for decoding Tiff images with UnassociatedAlphaData

src/ImageSharp/Formats/Tiff/PhotometricInterpretation/Rgb242424TiffColor{TPixel}.cs

@@ -30,10 +30,10 @@ public override void Decode(ReadOnlySpan<byte> data, Buffer2D<TPixel> pixels, in
             var color = default(TPixel);
             color.FromVector4(TiffUtils.Vector4Default);
             int offset = 0;
-            byte[] buffer = new byte[4];
+            Span<byte> buffer = stackalloc byte[4];
             int bufferStartIdx = this.isBigEndian ? 1 : 0;
 
-            Span<byte> bufferSpan = buffer.AsSpan(bufferStartIdx);
+            Span<byte> bufferSpan = buffer.Slice(bufferStartIdx);
             for (int y = top; y < top + height; y++)
             {
                 Span<TPixel> pixelRow = pixels.DangerousGetRowSpan(y).Slice(left, width);

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

@@ -30,13 +30,13 @@ public override void Decode(IMemoryOwner<byte>[] data, Buffer2D<TPixel> pixels,
             // 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];
+            Span<byte> buffer = stackalloc 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();
-            Span<byte> bufferSpan = buffer.AsSpan(bufferStartIdx);
+            Span<byte> bufferSpan = buffer.Slice(bufferStartIdx);
 
             int offset = 0;
             for (int y = top; y < top + height; y++)

src/ImageSharp/Formats/Tiff/PhotometricInterpretation/Rgba16161616TiffColor{TPixel}.cs

@@ -0,0 +1,77 @@
+// Copyright (c) Six Labors.
+// Licensed under the Apache License, Version 2.0.
+
+using System;
+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 an alpha channel and with 16 bits for each channel.
+    /// </summary>
+    internal class Rgba16161616TiffColor<TPixel> : TiffBaseColorDecoder<TPixel>
+        where TPixel : unmanaged, IPixel<TPixel>
+    {
+        private readonly bool isBigEndian;
+
+        private readonly Configuration configuration;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Rgba16161616TiffColor{TPixel}" /> class.
+        /// </summary>
+        /// <param name="configuration">The configuration.</param>
+        /// <param name="isBigEndian">if set to <c>true</c> decodes the pixel data as big endian, otherwise as little endian.</param>
+        public Rgba16161616TiffColor(Configuration configuration, bool isBigEndian)
+        {
+            this.configuration = configuration;
+            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
+            Rgba64 rgba = TiffUtils.Rgba64Default;
+            var color = default(TPixel);
+            color.FromVector4(TiffUtils.Vector4Default);
+
+            int offset = 0;
+
+            for (int y = top; y < top + height; y++)
+            {
+                Span<TPixel> pixelRow = pixels.DangerousGetRowSpan(y).Slice(left, width);
+
+                if (this.isBigEndian)
+                {
+                    for (int x = 0; x < pixelRow.Length; x++)
+                    {
+                        ulong r = TiffUtils.ConvertToUShortBigEndian(data.Slice(offset, 2));
+                        offset += 2;
+                        ulong g = TiffUtils.ConvertToUShortBigEndian(data.Slice(offset, 2));
+                        offset += 2;
+                        ulong b = TiffUtils.ConvertToUShortBigEndian(data.Slice(offset, 2));
+                        offset += 2;
+                        ulong a = TiffUtils.ConvertToUShortBigEndian(data.Slice(offset, 2));
+                        offset += 2;
+
+                        pixelRow[x] = TiffUtils.ColorFromRgba64(rgba, r, g, b, a, color);
+                    }
+                }
+                else
+                {
+                    int byteCount = pixelRow.Length * 8;
+                    PixelOperations<TPixel>.Instance.FromRgba64Bytes(
+                        this.configuration,
+                        data.Slice(offset, byteCount),
+                        pixelRow,
+                        pixelRow.Length);
+
+                    offset += byteCount;
+                }
+            }
+        }
+    }
+}

src/ImageSharp/Formats/Tiff/PhotometricInterpretation/Rgba16PlanarTiffColor{TPixel}.cs

@@ -0,0 +1,75 @@
+// Copyright (c) Six Labors.
+// Licensed under the Apache License, Version 2.0.
+
+using System;
+using System.Buffers;
+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 an alpha channel and with 'Planar' layout for each color channel with 16 bit.
+    /// </summary>
+    internal class Rgba16PlanarTiffColor<TPixel> : TiffBasePlanarColorDecoder<TPixel>
+        where TPixel : unmanaged, IPixel<TPixel>
+    {
+        private readonly bool isBigEndian;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Rgba16PlanarTiffColor{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 Rgba16PlanarTiffColor(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
+            Rgba64 rgba = TiffUtils.Rgba64Default;
+            var color = default(TPixel);
+            color.FromVector4(TiffUtils.Vector4Default);
+
+            Span<byte> redData = data[0].GetSpan();
+            Span<byte> greenData = data[1].GetSpan();
+            Span<byte> blueData = data[2].GetSpan();
+            Span<byte> alphaData = data[3].GetSpan();
+
+            int offset = 0;
+            for (int y = top; y < top + height; y++)
+            {
+                Span<TPixel> pixelRow = pixels.DangerousGetRowSpan(y).Slice(left, width);
+                if (this.isBigEndian)
+                {
+                    for (int x = 0; x < pixelRow.Length; x++)
+                    {
+                        ulong r = TiffUtils.ConvertToUShortBigEndian(redData.Slice(offset, 2));
+                        ulong g = TiffUtils.ConvertToUShortBigEndian(greenData.Slice(offset, 2));
+                        ulong b = TiffUtils.ConvertToUShortBigEndian(blueData.Slice(offset, 2));
+                        ulong a = TiffUtils.ConvertToUShortBigEndian(alphaData.Slice(offset, 2));
+
+                        offset += 2;
+
+                        pixelRow[x] = TiffUtils.ColorFromRgba64(rgba, r, g, b, a, color);
+                    }
+                }
+                else
+                {
+                    for (int x = 0; x < pixelRow.Length; x++)
+                    {
+                        ulong r = TiffUtils.ConvertToUShortLittleEndian(redData.Slice(offset, 2));
+                        ulong g = TiffUtils.ConvertToUShortLittleEndian(greenData.Slice(offset, 2));
+                        ulong b = TiffUtils.ConvertToUShortLittleEndian(blueData.Slice(offset, 2));
+                        ulong a = TiffUtils.ConvertToUShortBigEndian(alphaData.Slice(offset, 2));
+
+                        offset += 2;
+
+                        pixelRow[x] = TiffUtils.ColorFromRgba64(rgba, r, g, b, a, color);
+                    }
+                }
+            }
+        }
+    }
+}

src/ImageSharp/Formats/Tiff/PhotometricInterpretation/Rgba24242424TiffColor{TPixel}.cs

@@ -0,0 +1,90 @@
+// Copyright (c) Six Labors.
+// Licensed under the Apache License, Version 2.0.
+
+using System;
+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 an alpha channel and with 24 bits for each channel.
+    /// </summary>
+    internal class Rgba24242424TiffColor<TPixel> : TiffBaseColorDecoder<TPixel>
+        where TPixel : unmanaged, IPixel<TPixel>
+    {
+        private readonly bool isBigEndian;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Rgba24242424TiffColor{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 Rgba24242424TiffColor(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;
+            Span<byte> buffer = stackalloc byte[4];
+            int bufferStartIdx = this.isBigEndian ? 1 : 0;
+
+            Span<byte> bufferSpan = buffer.Slice(bufferStartIdx);
+            for (int y = top; y < top + height; y++)
+            {
+                Span<TPixel> pixelRow = pixels.DangerousGetRowSpan(y).Slice(left, width);
+
+                if (this.isBigEndian)
+                {
+                    for (int x = 0; x < pixelRow.Length; x++)
+                    {
+                        data.Slice(offset, 3).CopyTo(bufferSpan);
+                        ulong r = TiffUtils.ConvertToUIntBigEndian(buffer);
+                        offset += 3;
+
+                        data.Slice(offset, 3).CopyTo(bufferSpan);
+                        ulong g = TiffUtils.ConvertToUIntBigEndian(buffer);
+                        offset += 3;
+
+                        data.Slice(offset, 3).CopyTo(bufferSpan);
+                        ulong b = TiffUtils.ConvertToUIntBigEndian(buffer);
+                        offset += 3;
+
+                        data.Slice(offset, 3).CopyTo(bufferSpan);
+                        ulong a = TiffUtils.ConvertToUIntBigEndian(buffer);
+                        offset += 3;
+
+                        pixelRow[x] = TiffUtils.ColorScaleTo24Bit(r, g, b, a, color);
+                    }
+                }
+                else
+                {
+                    for (int x = 0; x < pixelRow.Length; x++)
+                    {
+                        data.Slice(offset, 3).CopyTo(bufferSpan);
+                        ulong r = TiffUtils.ConvertToUIntLittleEndian(buffer);
+                        offset += 3;
+
+                        data.Slice(offset, 3).CopyTo(bufferSpan);
+                        ulong g = TiffUtils.ConvertToUIntLittleEndian(buffer);
+                        offset += 3;
+
+                        data.Slice(offset, 3).CopyTo(bufferSpan);
+                        ulong b = TiffUtils.ConvertToUIntLittleEndian(buffer);
+                        offset += 3;
+
+                        data.Slice(offset, 3).CopyTo(bufferSpan);
+                        ulong a = TiffUtils.ConvertToUIntLittleEndian(buffer);
+                        offset += 3;
+
+                        pixelRow[x] = TiffUtils.ColorScaleTo24Bit(r, g, b, a, color);
+                    }
+                }
+            }
+        }
+    }
+}

src/ImageSharp/Formats/Tiff/PhotometricInterpretation/Rgba24PlanarTiffColor{TPixel}.cs

@@ -0,0 +1,85 @@
+// Copyright (c) Six Labors.
+// Licensed under the Apache License, Version 2.0.
+
+using System;
+using System.Buffers;
+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 an alpha channel and with 'Planar' layout for each color channel with 24 bit.
+    /// </summary>
+    internal class Rgba24PlanarTiffColor<TPixel> : TiffBasePlanarColorDecoder<TPixel>
+        where TPixel : unmanaged, IPixel<TPixel>
+    {
+        private readonly bool isBigEndian;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Rgba24PlanarTiffColor{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 Rgba24PlanarTiffColor(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);
+            Span<byte> buffer = stackalloc 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();
+            Span<byte> alphaData = data[3].GetSpan();
+            Span<byte> bufferSpan = buffer.Slice(bufferStartIdx);
+
+            int offset = 0;
+            for (int y = top; y < top + height; y++)
+            {
+                Span<TPixel> pixelRow = pixels.DangerousGetRowSpan(y).Slice(left, width);
+                if (this.isBigEndian)
+                {
+                    for (int x = 0; x < pixelRow.Length; x++)
+                    {
+                        redData.Slice(offset, 3).CopyTo(bufferSpan);
+                        ulong r = TiffUtils.ConvertToUIntBigEndian(buffer);
+                        greenData.Slice(offset, 3).CopyTo(bufferSpan);
+                        ulong g = TiffUtils.ConvertToUIntBigEndian(buffer);
+                        blueData.Slice(offset, 3).CopyTo(bufferSpan);
+                        ulong b = TiffUtils.ConvertToUIntBigEndian(buffer);
+                        alphaData.Slice(offset, 3).CopyTo(bufferSpan);
+                        ulong a = TiffUtils.ConvertToUIntBigEndian(buffer);
+
+                        offset += 3;
+
+                        pixelRow[x] = TiffUtils.ColorScaleTo24Bit(r, g, b, a, color);
+                    }
+                }
+                else
+                {
+                    for (int x = 0; x < pixelRow.Length; x++)
+                    {
+                        redData.Slice(offset, 3).CopyTo(bufferSpan);
+                        ulong r = TiffUtils.ConvertToUIntLittleEndian(buffer);
+                        greenData.Slice(offset, 3).CopyTo(bufferSpan);
+                        ulong g = TiffUtils.ConvertToUIntLittleEndian(buffer);
+                        blueData.Slice(offset, 3).CopyTo(bufferSpan);
+                        ulong b = TiffUtils.ConvertToUIntLittleEndian(buffer);
+                        alphaData.Slice(offset, 3).CopyTo(bufferSpan);
+                        ulong a = TiffUtils.ConvertToUIntLittleEndian(buffer);
+
+                        offset += 3;
+
+                        pixelRow[x] = TiffUtils.ColorScaleTo24Bit(r, g, b, a, color);
+                    }
+                }
+            }
+        }
+    }
+}