Add support for decoding Tiff images with associated alpha data

src/ImageSharp/Formats/Bmp/BmpDecoderCore.cs

@@ -323,12 +323,12 @@ private void ReadRle<TPixel>(BmpCompression compression, Buffer2D<TPixel> pixels
                                         color.FromBgr24(Unsafe.As<byte, Bgr24>(ref colors[colorIdx * 4]));
                                         break;
                                     case RleSkippedPixelHandling.Transparent:
-                                        color.FromVector4(Vector4.Zero);
+                                        color.FromScaledVector4(Vector4.Zero);
                                         break;
 
                                     // Default handling for skipped pixels is black (which is what System.Drawing is also doing).
                                     default:
-                                        color.FromVector4(new Vector4(0.0f, 0.0f, 0.0f, 1.0f));
+                                        color.FromScaledVector4(new Vector4(0.0f, 0.0f, 0.0f, 1.0f));
                                         break;
                                 }
                             }
@@ -395,12 +395,12 @@ private void ReadRle24<TPixel>(Buffer2D<TPixel> pixels, int width, int height, b
                                         color.FromBgr24(Unsafe.As<byte, Bgr24>(ref bufferSpan[idx]));
                                         break;
                                     case RleSkippedPixelHandling.Transparent:
-                                        color.FromVector4(Vector4.Zero);
+                                        color.FromScaledVector4(Vector4.Zero);
                                         break;
 
                                     // Default handling for skipped pixels is black (which is what System.Drawing is also doing).
                                     default:
-                                        color.FromVector4(new Vector4(0.0f, 0.0f, 0.0f, 1.0f));
+                                        color.FromScaledVector4(new Vector4(0.0f, 0.0f, 0.0f, 1.0f));
                                         break;
                                 }
                             }
@@ -1127,7 +1127,7 @@ private void ReadRgb32BitFields<TPixel>(Buffer2D<TPixel> pixels, int width, int
                             g * invMaxValueGreen,
                             b * invMaxValueBlue,
                             alpha);
-                        color.FromVector4(vector4);
+                        color.FromScaledVector4(vector4);
                     }
                     else
                     {

src/ImageSharp/Formats/Tiff/Constants/TiffCompression.cs

@@ -23,11 +23,6 @@ public enum TiffCompression : ushort
         /// </summary>
         Ccitt1D = 2,
 
-        /// <summary>
-        /// PackBits compression
-        /// </summary>
-        PackBits = 32773,
-
         /// <summary>
         /// T4-encoding: CCITT T.4 bi-level encoding (see Section 11 of the TIFF 6.0 specification).
         /// </summary>
@@ -65,27 +60,48 @@ public enum TiffCompression : ushort
         Deflate = 8,
 
         /// <summary>
-        /// Deflate compression - old.
+        /// ITU-T Rec. T.82 coding, applying ITU-T Rec. T.85 (JBIG) (see RFC2301).
         ///
-        /// Note: The TIFF encoder does not support this compression and will default to use no compression instead,
+        /// Note: The TIFF encoder does not yet support this compression and will default to use no compression instead,
         /// if this is chosen.
         /// </summary>
-        OldDeflate = 32946,
+        ItuTRecT82 = 9,
 
         /// <summary>
-        /// ITU-T Rec. T.82 coding, applying ITU-T Rec. T.85 (JBIG) (see RFC2301).
+        /// ITU-T Rec. T.43 representation, using ITU-T Rec. T.82 (JBIG) (see RFC2301).
         ///
         /// Note: The TIFF encoder does not yet support this compression and will default to use no compression instead,
         /// if this is chosen.
         /// </summary>
-        ItuTRecT82 = 9,
+        ItuTRecT43 = 10,
 
         /// <summary>
-        /// ITU-T Rec. T.43 representation, using ITU-T Rec. T.82 (JBIG) (see RFC2301).
+        /// NeXT 2-bit Grey Scale compression algorithm.
         ///
-        /// Note: The TIFF encoder does not yet support this compression and will default to use no compression instead,
+        /// Note: The TIFF encoder does not support this compression and will default to use no compression instead,
+        /// if this is chosen.
+        /// </summary>
+        NeXT = 32766,
+
+        /// <summary>
+        /// PackBits compression.
+        /// </summary>
+        PackBits = 32773,
+
+        /// <summary>
+        /// ThunderScan 4-bit compression.
+        ///
+        /// Note: The TIFF encoder does not support this compression and will default to use no compression instead,
         /// if this is chosen.
         /// </summary>
-        ItuTRecT43 = 10
+        ThunderScan = 32809,
+
+        /// <summary>
+        /// Deflate compression - old.
+        ///
+        /// Note: The TIFF encoder does not support this compression and will default to use no compression instead,
+        /// if this is chosen.
+        /// </summary>
+        OldDeflate = 32946,
     }
 }

src/ImageSharp/Formats/Tiff/PhotometricInterpretation/BlackIsZero16TiffColor{TPixel}.cs

@@ -36,7 +36,7 @@ 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
             L16 l16 = TiffUtils.L16Default;
             var color = default(TPixel);
-            color.FromVector4(TiffUtils.Vector4Default);
+            color.FromScaledVector4(TiffUtils.Vector4Default);
 
             int offset = 0;
             for (int y = top; y < top + height; y++)

src/ImageSharp/Formats/Tiff/PhotometricInterpretation/BlackIsZero24TiffColor{TPixel}.cs

@@ -28,7 +28,7 @@ public override void Decode(ReadOnlySpan<byte> data, Buffer2D<TPixel> pixels, in
             // 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);
+            color.FromScaledVector4(TiffUtils.Vector4Default);
             byte[] buffer = new byte[4];
             int bufferStartIdx = this.isBigEndian ? 1 : 0;
 

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

@@ -29,7 +29,7 @@ public override void Decode(ReadOnlySpan<byte> data, Buffer2D<TPixel> pixels, in
             // 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);
+            color.FromScaledVector4(TiffUtils.Vector4Default);
             byte[] buffer = new byte[4];
 
             int offset = 0;
@@ -46,7 +46,7 @@ public override void Decode(ReadOnlySpan<byte> data, Buffer2D<TPixel> pixels, in
                         offset += 4;
 
                         var colorVector = new Vector4(intensity, intensity, intensity, 1.0f);
-                        color.FromVector4(colorVector);
+                        color.FromScaledVector4(colorVector);
                         pixelRow[x] = color;
                     }
                 }
@@ -59,7 +59,7 @@ public override void Decode(ReadOnlySpan<byte> data, Buffer2D<TPixel> pixels, in
                         offset += 4;
 
                         var colorVector = new Vector4(intensity, intensity, intensity, 1.0f);
-                        color.FromVector4(colorVector);
+                        color.FromScaledVector4(colorVector);
                         pixelRow[x] = color;
                     }
                 }

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

@@ -28,7 +28,7 @@ public override void Decode(ReadOnlySpan<byte> data, Buffer2D<TPixel> pixels, in
             // 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);
+            color.FromScaledVector4(TiffUtils.Vector4Default);
 
             int offset = 0;
             for (int y = top; y < top + height; y++)

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

@@ -40,7 +40,7 @@ public override void Decode(ReadOnlySpan<byte> data, Buffer2D<TPixel> pixels, in
                     int value = bitReader.ReadBits(this.bitsPerSample0);
                     float intensity = value / this.factor;
 
-                    color.FromVector4(new Vector4(intensity, intensity, intensity, 1.0f));
+                    color.FromScaledVector4(new Vector4(intensity, intensity, intensity, 1.0f));
                     pixelRow[x] = color;
                 }
 

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

@@ -59,7 +59,7 @@ private static TPixel[] GeneratePalette(ushort[] colorMap, int colorCount)
                 float r = colorMap[rOffset + i] / 65535F;
                 float g = colorMap[gOffset + i] / 65535F;
                 float b = colorMap[bOffset + i] / 65535F;
-                palette[i].FromVector4(new Vector4(r, g, b, 1.0f));
+                palette[i].FromScaledVector4(new Vector4(r, g, b, 1.0f));
             }
 
             return palette;

src/ImageSharp/Formats/Tiff/PhotometricInterpretation/Rgb161616TiffColor{TPixel}.cs

@@ -36,7 +36,7 @@ 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
             Rgba64 rgba = TiffUtils.Rgba64Default;
             var color = default(TPixel);
-            color.FromVector4(TiffUtils.Vector4Default);
+            color.FromScaledVector4(TiffUtils.Vector4Default);
 
             int offset = 0;
 
@@ -55,7 +55,7 @@ public override void Decode(ReadOnlySpan<byte> data, Buffer2D<TPixel> pixels, in
                         ulong b = TiffUtils.ConvertToUShortBigEndian(data.Slice(offset, 2));
                         offset += 2;
 
-                        pixelRow[x] = TiffUtils.ColorFromRgba64(rgba, r, g, b, color);
+                        pixelRow[x] = TiffUtils.ColorFromRgb64(rgba, r, g, b, color);
                     }
                 }
                 else

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

@@ -30,7 +30,7 @@ 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
             Rgba64 rgba = TiffUtils.Rgba64Default;
             var color = default(TPixel);
-            color.FromVector4(TiffUtils.Vector4Default);
+            color.FromScaledVector4(TiffUtils.Vector4Default);
 
             Span<byte> redData = data[0].GetSpan();
             Span<byte> greenData = data[1].GetSpan();
@@ -50,7 +50,7 @@ public override void Decode(IMemoryOwner<byte>[] data, Buffer2D<TPixel> pixels,
 
                         offset += 2;
 
-                        pixelRow[x] = TiffUtils.ColorFromRgba64(rgba, r, g, b, color);
+                        pixelRow[x] = TiffUtils.ColorFromRgb64(rgba, r, g, b, color);
                     }
                 }
                 else
@@ -63,7 +63,7 @@ public override void Decode(IMemoryOwner<byte>[] data, Buffer2D<TPixel> pixels,
 
                         offset += 2;
 
-                        pixelRow[x] = TiffUtils.ColorFromRgba64(rgba, r, g, b, color);
+                        pixelRow[x] = TiffUtils.ColorFromRgb64(rgba, r, g, b, color);
                     }
                 }
             }

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

@@ -28,7 +28,7 @@ public override void Decode(ReadOnlySpan<byte> data, Buffer2D<TPixel> pixels, in
             // 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);
+            color.FromScaledVector4(TiffUtils.Vector4Default);
             int offset = 0;
             Span<byte> buffer = stackalloc byte[4];
             int bufferStartIdx = this.isBigEndian ? 1 : 0;

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

@@ -29,7 +29,7 @@ public override void Decode(IMemoryOwner<byte>[] data, Buffer2D<TPixel> pixels,
             // 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);
+            color.FromScaledVector4(TiffUtils.Vector4Default);
             Span<byte> buffer = stackalloc byte[4];
             int bufferStartIdx = this.isBigEndian ? 1 : 0;
 

src/ImageSharp/Formats/Tiff/PhotometricInterpretation/Rgb323232TiffColor{TPixel}.cs

@@ -28,7 +28,7 @@ public override void Decode(ReadOnlySpan<byte> data, Buffer2D<TPixel> pixels, in
             // 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);
+            color.FromScaledVector4(TiffUtils.Vector4Default);
             int offset = 0;
 
             for (int y = top; y < top + height; y++)

src/ImageSharp/Formats/Tiff/PhotometricInterpretation/Rgb32PlanarTiffColor{TPixel}.cs

@@ -29,7 +29,7 @@ public override void Decode(IMemoryOwner<byte>[] data, Buffer2D<TPixel> pixels,
             // 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);
+            color.FromScaledVector4(TiffUtils.Vector4Default);
 
             Span<byte> redData = data[0].GetSpan();
             Span<byte> greenData = data[1].GetSpan();

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

@@ -29,7 +29,7 @@ public override void Decode(ReadOnlySpan<byte> data, Buffer2D<TPixel> pixels, in
             // 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);
+            color.FromScaledVector4(TiffUtils.Vector4Default);
             int offset = 0;
             byte[] buffer = new byte[4];
 
@@ -57,7 +57,7 @@ public override void Decode(ReadOnlySpan<byte> data, Buffer2D<TPixel> pixels, in
                         offset += 4;
 
                         var colorVector = new Vector4(r, g, b, 1.0f);
-                        color.FromVector4(colorVector);
+                        color.FromScaledVector4(colorVector);
                         pixelRow[x] = color;
                     }
                 }
@@ -78,7 +78,7 @@ public override void Decode(ReadOnlySpan<byte> data, Buffer2D<TPixel> pixels, in
                         offset += 4;
 
                         var colorVector = new Vector4(r, g, b, 1.0f);
-                        color.FromVector4(colorVector);
+                        color.FromScaledVector4(colorVector);
                         pixelRow[x] = color;
                     }
                 }

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

@@ -65,7 +65,7 @@ public override void Decode(IMemoryOwner<byte>[] data, Buffer2D<TPixel> pixels,
                     float g = gBitReader.ReadBits(this.bitsPerSampleG) / this.gFactor;
                     float b = bBitReader.ReadBits(this.bitsPerSampleB) / this.bFactor;
 
-                    color.FromVector4(new Vector4(r, g, b, 1.0f));
+                    color.FromScaledVector4(new Vector4(r, g, b, 1.0f));
                     pixelRow[x] = color;
                 }
 

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

@@ -54,7 +54,7 @@ public override void Decode(ReadOnlySpan<byte> data, Buffer2D<TPixel> pixels, in
                     float g = bitReader.ReadBits(this.bitsPerSampleG) / this.gFactor;
                     float b = bitReader.ReadBits(this.bitsPerSampleB) / this.bFactor;
 
-                    color.FromVector4(new Vector4(r, g, b, 1.0f));
+                    color.FromScaledVector4(new Vector4(r, g, b, 1.0f));
                     pixelRow[x] = color;
                 }
 

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

@@ -2,6 +2,8 @@
 // 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;
@@ -18,15 +20,23 @@ internal class Rgba16161616TiffColor<TPixel> : TiffBaseColorDecoder<TPixel>
 
         private readonly Configuration configuration;
 
+        private readonly MemoryAllocator memoryAllocator;
+
+        private readonly TiffExtraSampleType? extraSamplesType;
+
         /// <summary>
         /// Initializes a new instance of the <see cref="Rgba16161616TiffColor{TPixel}" /> class.
         /// </summary>
         /// <param name="configuration">The configuration.</param>
+        /// <param name="memoryAllocator">The memory allocator.</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)
+        /// <param name="extraSamplesType">The type of the extra samples.</param>
+        public Rgba16161616TiffColor(Configuration configuration, MemoryAllocator memoryAllocator, TiffExtraSampleType? extraSamplesType, bool isBigEndian)
         {
             this.configuration = configuration;
             this.isBigEndian = isBigEndian;
+            this.memoryAllocator = memoryAllocator;
+            this.extraSamplesType = extraSamplesType;
         }
 
         /// <inheritdoc/>
@@ -36,10 +46,13 @@ 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
             Rgba64 rgba = TiffUtils.Rgba64Default;
             var color = default(TPixel);
-            color.FromVector4(TiffUtils.Vector4Default);
+            color.FromScaledVector4(TiffUtils.Vector4Default);
 
+            bool hasAssociatedAlpha = this.extraSamplesType.HasValue && this.extraSamplesType == TiffExtraSampleType.AssociatedAlphaData;
             int offset = 0;
 
+            using IMemoryOwner<Vector4> vectors = hasAssociatedAlpha ? this.memoryAllocator.Allocate<Vector4>(width) : null;
+            Span<Vector4> vectorsSpan = hasAssociatedAlpha ? vectors.GetSpan() : Span<Vector4>.Empty;
             for (int y = top; y < top + height; y++)
             {
                 Span<TPixel> pixelRow = pixels.DangerousGetRowSpan(y).Slice(left, width);
@@ -57,7 +70,9 @@ public override void Decode(ReadOnlySpan<byte> data, Buffer2D<TPixel> pixels, in
                         ulong a = TiffUtils.ConvertToUShortBigEndian(data.Slice(offset, 2));
                         offset += 2;
 
-                        pixelRow[x] = TiffUtils.ColorFromRgba64(rgba, r, g, b, a, color);
+                        pixelRow[x] = hasAssociatedAlpha ?
+                            TiffUtils.ColorFromRgba64Premultiplied(rgba, r, g, b, a, color) :
+                            TiffUtils.ColorFromRgba64(rgba, r, g, b, a, color);
                     }
                 }
                 else
@@ -69,6 +84,12 @@ public override void Decode(ReadOnlySpan<byte> data, Buffer2D<TPixel> pixels, in
                         pixelRow,
                         pixelRow.Length);
 
+                    if (hasAssociatedAlpha)
+                    {
+                        PixelOperations<TPixel>.Instance.ToVector4(this.configuration, pixelRow, vectorsSpan);
+                        PixelOperations<TPixel>.Instance.FromVector4Destructive(this.configuration, vectorsSpan, pixelRow, PixelConversionModifiers.Premultiply | PixelConversionModifiers.Scale);
+                    }
+
                     offset += byteCount;
                 }
             }