Undo horizontal prediction for each tile row in case of tiled tiff's

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

@@ -22,6 +22,8 @@ internal sealed class DeflateTiffCompression : TiffBaseDecompressor
 
     private readonly TiffColorType colorType;
 
+    private readonly bool isTiled;
+
     /// <summary>
     /// Initializes a new instance of the <see cref="DeflateTiffCompression" /> class.
     /// </summary>
@@ -31,11 +33,13 @@ internal sealed class DeflateTiffCompression : TiffBaseDecompressor
     /// <param name="colorType">The color type of the pixel data.</param>
     /// <param name="predictor">The tiff predictor used.</param>
     /// <param name="isBigEndian">if set to <c>true</c> decodes the pixel data as big endian, otherwise as little endian.</param>
-    public DeflateTiffCompression(MemoryAllocator memoryAllocator, int width, int bitsPerPixel, TiffColorType colorType, TiffPredictor predictor, bool isBigEndian)
+    /// <param name="isTiled">Flag indicates, if the image is a tiled image.</param>
+    public DeflateTiffCompression(MemoryAllocator memoryAllocator, int width, int bitsPerPixel, TiffColorType colorType, TiffPredictor predictor, bool isBigEndian, bool isTiled)
         : base(memoryAllocator, width, bitsPerPixel, predictor)
     {
         this.colorType = colorType;
         this.isBigEndian = isBigEndian;
+        this.isTiled = isTiled;
     }
 
     /// <inheritdoc/>
@@ -68,7 +72,8 @@ internal sealed class DeflateTiffCompression : TiffBaseDecompressor
             }
         }
 
-        if (this.Predictor == TiffPredictor.Horizontal)
+        // When the image is tiled, undoing the horizontal predictor will be done for each tile row in the DecodeTilesChunky() method.
+        if (this.Predictor == TiffPredictor.Horizontal && !this.isTiled)
         {
             HorizontalPredictor.Undo(buffer, this.Width, this.colorType, this.isBigEndian);
         }

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

@@ -62,6 +62,22 @@ internal static class HorizontalPredictor
         }
     }
 
+    public static void UndoRow(Span<byte> pixelBytes, int width, int y, TiffColorType colorType)
+    {
+        // TODO: Implement missing colortypes, see above.
+        switch (colorType)
+        {
+            case TiffColorType.Rgb888:
+            case TiffColorType.CieLab:
+                UndoRgb24BitRow(pixelBytes, width, y);
+                break;
+            case TiffColorType.Rgba8888:
+            case TiffColorType.Cmyk:
+                UndoRgba32BitRow(pixelBytes, width, y);
+                break;
+        }
+    }
+
     public static void ApplyHorizontalPrediction(Span<byte> rows, int width, int bitsPerPixel)
     {
         if (bitsPerPixel == 8)
@@ -257,12 +273,9 @@ internal static class HorizontalPredictor
         }
     }
 
-    private static void UndoRgb24Bit(Span<byte> pixelBytes, int width)
+    private static void UndoRgb24BitRow(Span<byte> pixelBytes, int width, int y)
     {
         int rowBytesCount = width * 3;
-        int height = pixelBytes.Length / rowBytesCount;
-        for (int y = 0; y < height; y++)
-        {
         Span<byte> rowBytes = pixelBytes.Slice(y * rowBytesCount, rowBytesCount);
         Span<Rgb24> rowRgb = MemoryMarshal.Cast<byte, Rgb24>(rowBytes)[..width];
         ref Rgb24 rowRgbBase = ref MemoryMarshal.GetReference(rowRgb);
@@ -279,14 +292,21 @@ internal static class HorizontalPredictor
             pixel = new Rgb24(r, g, b);
         }
     }
-    }
 
-    private static void UndoRgba32Bit(Span<byte> pixelBytes, int width)
+    private static void UndoRgb24Bit(Span<byte> pixelBytes, int width)
     {
-        int rowBytesCount = width * 4;
+        int rowBytesCount = width * 3;
         int height = pixelBytes.Length / rowBytesCount;
         for (int y = 0; y < height; y++)
         {
+            UndoRgb24BitRow(pixelBytes, width, y);
+        }
+    }
+
+    private static void UndoRgba32BitRow(Span<byte> pixelBytes, int width, int y)
+    {
+        int rowBytesCount = width * 4;
+
         Span<byte> rowBytes = pixelBytes.Slice(y * rowBytesCount, rowBytesCount);
         Span<Rgba32> rowRgb = MemoryMarshal.Cast<byte, Rgba32>(rowBytes)[..width];
         ref Rgba32 rowRgbBase = ref MemoryMarshal.GetReference(rowRgb);
@@ -305,6 +325,15 @@ internal static class HorizontalPredictor
             pixel = new Rgba32(r, g, b, a);
         }
     }
+
+    private static void UndoRgba32Bit(Span<byte> pixelBytes, int width)
+    {
+        int rowBytesCount = width * 4;
+        int height = pixelBytes.Length / rowBytesCount;
+        for (int y = 0; y < height; y++)
+        {
+            UndoRgba32BitRow(pixelBytes, width, y);
+        }
     }
 
     private static void UndoRgb48Bit(Span<byte> pixelBytes, int width, bool isBigEndian)

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

@@ -24,7 +24,8 @@ internal static class TiffDecompressorsFactory
         byte[] jpegTables,
         uint oldJpegStartOfImageMarker,
         TiffFillOrder fillOrder,
-        ByteOrder byteOrder)
+        ByteOrder byteOrder,
+        bool isTiled = false)
     {
         switch (method)
         {
@@ -40,7 +41,7 @@ internal static class TiffDecompressorsFactory
 
             case TiffDecoderCompressionType.Deflate:
                 DebugGuard.IsTrue(faxOptions == FaxCompressionOptions.None, "No fax compression options are expected");
-                return new DeflateTiffCompression(allocator, width, bitsPerPixel, colorType, predictor, byteOrder == ByteOrder.BigEndian);
+                return new DeflateTiffCompression(allocator, width, bitsPerPixel, colorType, predictor, byteOrder == ByteOrder.BigEndian, isTiled);
 
             case TiffDecoderCompressionType.Lzw:
                 DebugGuard.IsTrue(faxOptions == FaxCompressionOptions.None, "No fax compression options are expected");

src/ImageSharp/Formats/Tiff/TiffDecoderCore.cs

@@ -683,7 +683,8 @@ internal class TiffDecoderCore : ImageDecoderCore
         Span<byte> tileBufferSpan = tileBuffer.GetSpan();
         Span<byte> uncompressedPixelBufferSpan = uncompressedPixelBuffer.GetSpan();
 
-        using TiffBaseDecompressor decompressor = this.CreateDecompressor<TPixel>(frame.Width, bitsPerPixel);
+        bool isTiled = true;
+        using TiffBaseDecompressor decompressor = this.CreateDecompressor<TPixel>(frame.Width, bitsPerPixel, isTiled);
         TiffBaseColorDecoder<TPixel> colorDecoder = this.CreateChunkyColorDecoder<TPixel>();
 
         int tileIndex = 0;
@@ -712,6 +713,13 @@ internal class TiffDecoderCore : ImageDecoderCore
                 {
                     Span<byte> uncompressedPixelRow = uncompressedPixelBufferSpan.Slice(uncompressedPixelBufferOffset, bytesToCopy);
                     tileBufferSpan.Slice(tileBufferOffset, bytesToCopy).CopyTo(uncompressedPixelRow);
+
+                    // Undo the horziontal predictor for each tile row.
+                    if (this.Predictor == TiffPredictor.Horizontal)
+                    {
+                        HorizontalPredictor.UndoRow(uncompressedPixelRow, tileLength, 0, this.ColorType);
+                    }
+
                     tileBufferOffset += bytesPerTileRow;
                     uncompressedPixelBufferOffset += bytesPerRow;
                 }
@@ -750,7 +758,7 @@ internal class TiffDecoderCore : ImageDecoderCore
             this.YcbcrSubSampling,
             this.byteOrder);
 
-    private TiffBaseDecompressor CreateDecompressor<TPixel>(int frameWidth, int bitsPerPixel)
+    private TiffBaseDecompressor CreateDecompressor<TPixel>(int frameWidth, int bitsPerPixel, bool isTiled = false)
         where TPixel : unmanaged, IPixel<TPixel> =>
         TiffDecompressorsFactory.Create(
             this.Options,
@@ -765,7 +773,8 @@ internal class TiffDecoderCore : ImageDecoderCore
             this.JpegTables,
             this.OldJpegCompressionStartOfImageMarker.GetValueOrDefault(),
             this.FillOrder,
-            this.byteOrder);
+            this.byteOrder,
+            isTiled);
 
     private IMemoryOwner<ulong> ConvertNumbers(Array array, out Span<ulong> span)
     {

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

@@ -23,7 +23,7 @@ public class DeflateTiffCompressionTests
         using BufferedReadStream stream = CreateCompressedStream(data);
         byte[] buffer = new byte[data.Length];
 
-        using var decompressor = new DeflateTiffCompression(Configuration.Default.MemoryAllocator, 10, 8, TiffColorType.BlackIsZero8, TiffPredictor.None, false);
+        using var decompressor = new DeflateTiffCompression(Configuration.Default.MemoryAllocator, 10, 8, TiffColorType.BlackIsZero8, TiffPredictor.None, false, false);
 
         decompressor.Decompress(stream, 0, (uint)stream.Length, 1, buffer, default);