Add support for horizontal predictor for 16 bit gray tiff's

src/ImageSharp/Formats/Tiff/Compression/Decompressors/DeflateTiffCompression.cs

@@ -5,7 +5,6 @@ using System;
 using System.IO.Compression;
 
 using SixLabors.ImageSharp.Compression.Zlib;
-using SixLabors.ImageSharp.Formats.Tiff.Compression;
 using SixLabors.ImageSharp.Formats.Tiff.Constants;
 using SixLabors.ImageSharp.IO;
 using SixLabors.ImageSharp.Memory;
@@ -20,6 +19,8 @@ namespace SixLabors.ImageSharp.Formats.Tiff.Compression.Decompressors
     /// </remarks>
     internal class DeflateTiffCompression : TiffBaseDecompressor
     {
+        private readonly bool isBigEndian;
+
         /// <summary>
         /// Initializes a new instance of the <see cref="DeflateTiffCompression" /> class.
         /// </summary>
@@ -27,10 +28,9 @@ namespace SixLabors.ImageSharp.Formats.Tiff.Compression.Decompressors
         /// <param name="width">The image width.</param>
         /// <param name="bitsPerPixel">The bits used per pixel.</param>
         /// <param name="predictor">The tiff predictor used.</param>
-        public DeflateTiffCompression(MemoryAllocator memoryAllocator, int width, int bitsPerPixel, TiffPredictor predictor)
+        /// <param name="isBigEndian">if set to <c>true</c> decodes the pixel data as big endian, otherwise as little endian.</param>
-            : base(memoryAllocator, width, bitsPerPixel, predictor)
+        public DeflateTiffCompression(MemoryAllocator memoryAllocator, int width, int bitsPerPixel, TiffPredictor predictor, bool isBigEndian)
-        {
+            : base(memoryAllocator, width, bitsPerPixel, predictor) => this.isBigEndian = isBigEndian;
-        }
 
         /// <inheritdoc/>
         protected override void Decompress(BufferedReadStream stream, int byteCount, Span<byte> buffer)
@@ -62,7 +62,7 @@ namespace SixLabors.ImageSharp.Formats.Tiff.Compression.Decompressors
 
             if (this.Predictor == TiffPredictor.Horizontal)
             {
-                HorizontalPredictor.Undo(buffer, this.Width, this.BitsPerPixel);
+                HorizontalPredictor.Undo(buffer, this.Width, this.BitsPerPixel, this.isBigEndian);
             }
         }
 

src/ImageSharp/Formats/Tiff/Compression/Decompressors/LzwTiffCompression.cs

@@ -13,6 +13,8 @@ namespace SixLabors.ImageSharp.Formats.Tiff.Compression.Decompressors
     /// </summary>
     internal class LzwTiffCompression : TiffBaseDecompressor
     {
+        private readonly bool isBigEndian;
+
         /// <summary>
         /// Initializes a new instance of the <see cref="LzwTiffCompression" /> class.
         /// </summary>
@@ -20,10 +22,9 @@ namespace SixLabors.ImageSharp.Formats.Tiff.Compression.Decompressors
         /// <param name="width">The image width.</param>
         /// <param name="bitsPerPixel">The bits used per pixel.</param>
         /// <param name="predictor">The tiff predictor used.</param>
-        public LzwTiffCompression(MemoryAllocator memoryAllocator, int width, int bitsPerPixel, TiffPredictor predictor)
+        /// <param name="isBigEndian">if set to <c>true</c> decodes the pixel data as big endian, otherwise as little endian.</param>
-            : base(memoryAllocator, width, bitsPerPixel, predictor)
+        public LzwTiffCompression(MemoryAllocator memoryAllocator, int width, int bitsPerPixel, TiffPredictor predictor, bool isBigEndian)
-        {
+            : base(memoryAllocator, width, bitsPerPixel, predictor) => this.isBigEndian = isBigEndian;
-        }
 
         /// <inheritdoc/>
         protected override void Decompress(BufferedReadStream stream, int byteCount, Span<byte> buffer)
@@ -33,7 +34,7 @@ namespace SixLabors.ImageSharp.Formats.Tiff.Compression.Decompressors
 
             if (this.Predictor == TiffPredictor.Horizontal)
             {
-                HorizontalPredictor.Undo(buffer, this.Width, this.BitsPerPixel);
+                HorizontalPredictor.Undo(buffer, this.Width, this.BitsPerPixel, this.isBigEndian);
             }
         }
 

src/ImageSharp/Formats/Tiff/Compression/HorizontalPredictor.cs

@@ -2,9 +2,10 @@
 // Licensed under the Apache License, Version 2.0.
 
 using System;
+using System.Buffers.Binary;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
-
+using SixLabors.ImageSharp.Formats.Tiff.Utils;
 using SixLabors.ImageSharp.PixelFormats;
 
 namespace SixLabors.ImageSharp.Formats.Tiff.Compression
@@ -20,12 +21,17 @@ namespace SixLabors.ImageSharp.Formats.Tiff.Compression
         /// <param name="pixelBytes">Buffer with decompressed pixel data.</param>
         /// <param name="width">The width of the image or strip.</param>
         /// <param name="bitsPerPixel">Bits per pixel.</param>
-        public static void Undo(Span<byte> pixelBytes, int width, int bitsPerPixel)
+        /// <param name="isBigEndian">if set to <c>true</c> decodes the pixel data as big endian, otherwise as little endian.</param>
+        public static void Undo(Span<byte> pixelBytes, int width, int bitsPerPixel, bool isBigEndian)
         {
             if (bitsPerPixel == 8)
             {
                 Undo8Bit(pixelBytes, width);
             }
+            else if (bitsPerPixel == 16)
+            {
+                Undo16Bit(pixelBytes, width, isBigEndian);
+            }
             else if (bitsPerPixel == 24)
             {
                 Undo24Bit(pixelBytes, width);
@@ -110,6 +116,50 @@ namespace SixLabors.ImageSharp.Formats.Tiff.Compression
             }
         }
 
+        private static void Undo16Bit(Span<byte> pixelBytes, int width, bool isBigEndian)
+        {
+            int rowBytesCount = width * 2;
+            int height = pixelBytes.Length / rowBytesCount;
+            if (isBigEndian)
+            {
+                for (int y = 0; y < height; y++)
+                {
+                    int offset = 0;
+                    Span<byte> rowBytes = pixelBytes.Slice(y * rowBytesCount, rowBytesCount);
+                    ushort pixelValue = TiffUtils.ConvertToUShortBigEndian(rowBytes.Slice(offset, 2));
+                    offset += 2;
+
+                    for (int x = 1; x < width; x++)
+                    {
+                        Span<byte> rowSpan = rowBytes.Slice(offset, 2);
+                        ushort diff = TiffUtils.ConvertToUShortBigEndian(rowSpan);
+                        pixelValue += diff;
+                        BinaryPrimitives.WriteUInt16BigEndian(rowSpan, pixelValue);
+                        offset += 2;
+                    }
+                }
+            }
+            else
+            {
+                for (int y = 0; y < height; y++)
+                {
+                    int offset = 0;
+                    Span<byte> rowBytes = pixelBytes.Slice(y * rowBytesCount, rowBytesCount);
+                    ushort pixelValue = TiffUtils.ConvertToUShortLittleEndian(rowBytes.Slice(offset, 2));
+                    offset += 2;
+
+                    for (int x = 1; x < width; x++)
+                    {
+                        Span<byte> rowSpan = rowBytes.Slice(offset, 2);
+                        ushort diff = TiffUtils.ConvertToUShortLittleEndian(rowSpan);
+                        pixelValue += diff;
+                        BinaryPrimitives.WriteUInt16LittleEndian(rowSpan, pixelValue);
+                        offset += 2;
+                    }
+                }
+            }
+        }
+
         private static void Undo24Bit(Span<byte> pixelBytes, int width)
         {
             int rowBytesCount = width * 3;

src/ImageSharp/Formats/Tiff/Compression/TiffDecompressorsFactory.cs

@@ -16,7 +16,8 @@ namespace SixLabors.ImageSharp.Formats.Tiff.Compression
             int width,
             int bitsPerPixel,
             TiffPredictor predictor,
-            FaxCompressionOptions faxOptions)
+            FaxCompressionOptions faxOptions,
+            ByteOrder byteOrder)
         {
             switch (method)
             {
@@ -32,11 +33,11 @@ namespace SixLabors.ImageSharp.Formats.Tiff.Compression
 
                 case TiffDecoderCompressionType.Deflate:
                     DebugGuard.IsTrue(faxOptions == FaxCompressionOptions.None, "No fax compression options are expected");
-                    return new DeflateTiffCompression(allocator, width, bitsPerPixel, predictor);
+                    return new DeflateTiffCompression(allocator, width, bitsPerPixel, predictor, byteOrder == ByteOrder.BigEndian);
 
                 case TiffDecoderCompressionType.Lzw:
                     DebugGuard.IsTrue(faxOptions == FaxCompressionOptions.None, "No fax compression options are expected");
-                    return new LzwTiffCompression(allocator, width, bitsPerPixel, predictor);
+                    return new LzwTiffCompression(allocator, width, bitsPerPixel, predictor, byteOrder == ByteOrder.BigEndian);
 
                 case TiffDecoderCompressionType.T4:
                     DebugGuard.IsTrue(predictor == TiffPredictor.None, "Predictor should only be used with lzw or deflate compression");

src/ImageSharp/Formats/Tiff/TiffDecoderCore.cs

@@ -264,7 +264,15 @@ namespace SixLabors.ImageSharp.Formats.Tiff
                     stripBuffers[stripIndex] = this.memoryAllocator.Allocate<byte>(uncompressedStripSize);
                 }
 
-                using TiffBaseDecompressor decompressor = TiffDecompressorsFactory.Create(this.CompressionType, this.memoryAllocator, this.PhotometricInterpretation, frame.Width, bitsPerPixel, this.Predictor, this.FaxCompressionOptions);
+                using TiffBaseDecompressor decompressor = TiffDecompressorsFactory.Create(
+                    this.CompressionType,
+                    this.memoryAllocator,
+                    this.PhotometricInterpretation,
+                    frame.Width,
+                    bitsPerPixel,
+                    this.Predictor,
+                    this.FaxCompressionOptions,
+                    this.byteOrder);
 
                 TiffBasePlanarColorDecoder<TPixel> colorDecoder = TiffColorDecoderFactory<TPixel>.CreatePlanar(this.ColorType, this.BitsPerSample, this.ColorMap, this.byteOrder);
 
@@ -314,7 +322,8 @@ namespace SixLabors.ImageSharp.Formats.Tiff
                 frame.Width,
                 bitsPerPixel,
                 this.Predictor,
-                this.FaxCompressionOptions);
+                this.FaxCompressionOptions,
+                this.byteOrder);
 
             TiffBaseColorDecoder<TPixel> colorDecoder = TiffColorDecoderFactory<TPixel>.Create(this.Configuration, this.ColorType, this.BitsPerSample, this.ColorMap, this.byteOrder);
 

tests/ImageSharp.Tests/Formats/Tiff/Compression/DeflateTiffCompressionTests.cs

@@ -26,7 +26,7 @@ namespace SixLabors.ImageSharp.Tests.Formats.Tiff.Compression
             {
                 var buffer = new byte[data.Length];
 
-                using var decompressor = new DeflateTiffCompression(Configuration.Default.MemoryAllocator, 10, 8, TiffPredictor.None);
+                using var decompressor = new DeflateTiffCompression(Configuration.Default.MemoryAllocator, 10, 8, TiffPredictor.None, false);
 
                 decompressor.Decompress(stream, 0, (uint)stream.Length, buffer);
 

tests/ImageSharp.Tests/Formats/Tiff/Compression/LzwTiffCompressionTests.cs

@@ -38,7 +38,7 @@ namespace SixLabors.ImageSharp.Tests.Formats.Tiff.Compression
             using BufferedReadStream stream = CreateCompressedStream(data);
             var buffer = new byte[data.Length];
 
-            using var decompressor = new LzwTiffCompression(Configuration.Default.MemoryAllocator, 10, 8, TiffPredictor.None);
+            using var decompressor = new LzwTiffCompression(Configuration.Default.MemoryAllocator, 10, 8, TiffPredictor.None, false);
             decompressor.Decompress(stream, 0, (uint)stream.Length, buffer);
 
             Assert.Equal(data, buffer);

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

@@ -161,6 +161,12 @@ namespace SixLabors.ImageSharp.Tests.Formats.Tiff
         public void TiffDecoder_CanDecode_16Bit_Gray<TPixel>(TestImageProvider<TPixel> provider)
             where TPixel : unmanaged, IPixel<TPixel> => TestTiffDecoder(provider);
 
+        [Theory]
+        [WithFile(Flower16BitGrayPredictorBigEndian, PixelTypes.Rgba32)]
+        [WithFile(Flower16BitGrayPredictorLittleEndian, PixelTypes.Rgba32)]
+        public void TiffDecoder_CanDecode_16Bit_Gray_WithPredictor<TPixel>(TestImageProvider<TPixel> provider)
+            where TPixel : unmanaged, IPixel<TPixel> => TestTiffDecoder(provider);
+
         [Theory]
         [WithFile(Flower24BitGray, PixelTypes.Rgba32)]
         [WithFile(Flower24BitGrayLittleEndian, PixelTypes.Rgba32)]

tests/ImageSharp.Tests/TestImages.cs

@@ -599,6 +599,8 @@ namespace SixLabors.ImageSharp.Tests
             public const string Flower16BitGrayLittleEndian = "Tiff/flower-minisblack-16_lsb.tiff";
             public const string Flower16BitGrayMinIsWhiteLittleEndian = "Tiff/flower-miniswhite-16_lsb.tiff";
             public const string Flower16BitGrayMinIsWhiteBigEndian = "Tiff/flower-miniswhite-16.tiff";
+            public const string Flower16BitGrayPredictorBigEndian = "Tiff/flower-minisblack-16_msb_lzw_predictor.tiff";
+            public const string Flower16BitGrayPredictorLittleEndian = "Tiff/flower-minisblack-16_lsb_lzw_predictor.tiff";
             public const string Flower24BitGray = "Tiff/flower-minisblack-24.tiff";
             public const string Flower24BitGrayLittleEndian = "Tiff/flower-minisblack-24_lsb.tiff";
             public const string Flower32BitGray = "Tiff/flower-minisblack-32.tiff";

tests/Images/Input/Tiff/flower-minisblack-16_lsb_lzw_predictor.tiff

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:263da6b84862af1bc23f2631e648b1a629b5571b253c82f3ea64f44e9b7b1fe6
+size 8478

tests/Images/Input/Tiff/flower-minisblack-16_msb_lzw_predictor.tiff

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:e67ac19cbdeb8585b204ee958edc7679a92c2b415a1a2c6051f14fe2966f933c
+size 8504