Add support for decoding jpeg's with arithmetic coding

src/ImageSharp/Formats/Bmp/BmpDecoderCore.cs

@@ -116,7 +116,7 @@ namespace SixLabors.ImageSharp.Formats.Bmp
         /// <summary>
         /// Gets the dimensions of the image.
         /// </summary>
-        public Size Dimensions => new Size(this.infoHeader.Width, this.infoHeader.Height);
+        public Size Dimensions => new(this.infoHeader.Width, this.infoHeader.Height);
 
         /// <inheritdoc />
         public Image<TPixel> Decode<TPixel>(BufferedReadStream stream, CancellationToken cancellationToken)
@@ -382,7 +382,7 @@ namespace SixLabors.ImageSharp.Formats.Bmp
                     if (rowHasUndefinedPixels)
                     {
                         // Slow path with undefined pixels.
-                        var yMulWidth = y * width;
+                        int yMulWidth = y * width;
                         int rowStartIdx = yMulWidth * 3;
                         for (int x = 0; x < width; x++)
                         {

src/ImageSharp/Formats/Jpeg/Components/ComponentType.cs

@@ -0,0 +1,12 @@
+// Copyright (c) Six Labors.
+// Licensed under the Apache License, Version 2.0.
+
+namespace SixLabors.ImageSharp.Formats.Jpeg.Components
+{
+    internal enum ComponentType
+    {
+        Huffman = 0,
+
+        Arithmetic = 1
+    }
+}

src/ImageSharp/Formats/Jpeg/Components/Decoder/ArithmeticDecodingComponent.cs

@@ -0,0 +1,30 @@
+// Copyright (c) Six Labors.
+// Licensed under the Apache License, Version 2.0.
+
+using SixLabors.ImageSharp.Memory;
+
+namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
+{
+    internal class ArithmeticDecodingComponent : JpegComponent
+    {
+        public ArithmeticDecodingComponent(MemoryAllocator memoryAllocator, JpegFrame frame, byte id, int horizontalFactor, int verticalFactor, byte quantizationTableIndex, int index)
+            : base(memoryAllocator, frame, id, horizontalFactor, verticalFactor, quantizationTableIndex, index)
+        {
+        }
+
+        /// <summary>
+        /// Gets or sets the dc context.
+        /// </summary>
+        public int DcContext { get; set; }
+
+        /// <summary>
+        /// Gets or sets the dc statistics.
+        /// </summary>
+        public ArithmeticStatistics DcStatistics { get; set; }
+
+        /// <summary>
+        /// Gets or sets the ac statistics.
+        /// </summary>
+        public ArithmeticStatistics AcStatistics { get; set; }
+    }
+}

src/ImageSharp/Formats/Jpeg/Components/Decoder/ArithmeticDecodingTable.cs

@@ -0,0 +1,43 @@
+// Copyright (c) Six Labors.
+// Licensed under the Apache License, Version 2.0.
+
+namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
+{
+    internal class ArithmeticDecodingTable
+    {
+        public ArithmeticDecodingTable(byte tableClass, byte identifier)
+        {
+            this.TableClass = tableClass;
+            this.Identifier = identifier;
+        }
+
+        public byte TableClass { get; }
+
+        public byte Identifier { get; }
+
+        public byte ConditioningTableValue { get; private set; }
+
+        public int DcL { get; private set; }
+
+        public int DcU { get; private set; }
+
+        public int AcKx { get; private set; }
+
+        public void Configure(byte conditioningTableValue)
+        {
+            this.ConditioningTableValue = conditioningTableValue;
+            if (this.TableClass == 0)
+            {
+                this.DcL = conditioningTableValue & 0x0F;
+                this.DcU = conditioningTableValue >> 4;
+                this.AcKx = 0;
+            }
+            else
+            {
+                this.DcL = 0;
+                this.DcU = 0;
+                this.AcKx = conditioningTableValue;
+            }
+        }
+    }
+}

src/ImageSharp/Formats/Jpeg/Components/Decoder/ArithmeticStatistics.cs

@@ -0,0 +1,29 @@
+// Copyright (c) Six Labors.
+// Licensed under the Apache License, Version 2.0.
+
+using System;
+
+namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
+{
+    internal class ArithmeticStatistics
+    {
+        private readonly byte[] statistics;
+
+        public ArithmeticStatistics(bool dc, int identifier)
+        {
+            this.IsDcStatistics = dc;
+            this.Identifier = identifier;
+            this.statistics = dc ? new byte[64] : new byte[256];
+        }
+
+        public bool IsDcStatistics { get; private set; }
+
+        public int Identifier { get; private set; }
+
+        public ref byte GetReference() => ref this.statistics[0];
+
+        public ref byte GetReference(int offset) => ref this.statistics[offset];
+
+        public void Reset() => this.statistics.AsSpan().Clear();
+    }
+}

src/ImageSharp/Formats/Jpeg/Components/Decoder/HuffmanScanDecoder.cs

@@ -14,7 +14,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
     /// Originally ported from <see href="https://github.com/t0rakka/mango"/>
     /// with additional fixes for both performance and common encoding errors.
     /// </summary>
-    internal class HuffmanScanDecoder
+    internal class HuffmanScanDecoder : IJpegScanDecoder
     {
         private readonly BufferedReadStream stream;
 
@@ -26,7 +26,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
         /// <summary>
         /// Shortcut for <see cref="frame"/>.Components.
         /// </summary>
-        private JpegComponent[] components;
+        private IJpegComponent[] components;
 
         /// <summary>
         /// Number of component in the current scan.
@@ -54,11 +54,11 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
         private readonly HuffmanTable[] dcHuffmanTables;
 
         /// <summary>
-        /// The AC Huffman tables
+        /// The AC Huffman tables.
         /// </summary>
         private readonly HuffmanTable[] acHuffmanTables;
 
-        private HuffmanScanBuffer scanBuffer;
+        private JpegBitReader scanBuffer;
 
         private readonly SpectralConverter spectralConverter;
 
@@ -119,7 +119,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
 
             this.scanComponentCount = scanComponentCount;
 
-            this.scanBuffer = new HuffmanScanBuffer(this.stream);
+            this.scanBuffer = new JpegBitReader(this.stream);
 
             bool fullScan = this.frame.Progressive || this.frame.MultiScan;
             this.frame.AllocateComponents(fullScan);
@@ -139,6 +139,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
             }
         }
 
+        /// <inheritdoc/>
         public void InjectFrameData(JpegFrame frame, IRawJpegData jpegData)
         {
             this.frame = frame;
@@ -170,7 +171,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
             int mcu = 0;
             int mcusPerColumn = this.frame.McusPerColumn;
             int mcusPerLine = this.frame.McusPerLine;
-            ref HuffmanScanBuffer buffer = ref this.scanBuffer;
+            ref JpegBitReader buffer = ref this.scanBuffer;
 
             for (int j = 0; j < mcusPerColumn; j++)
             {
@@ -184,10 +185,10 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
                     for (int k = 0; k < this.scanComponentCount; k++)
                     {
                         int order = this.frame.ComponentOrder[k];
-                        JpegComponent component = this.components[order];
+                        var component = this.components[order] as JpegComponent;
 
-                        ref HuffmanTable dcHuffmanTable = ref this.dcHuffmanTables[component.DCHuffmanTableId];
-                        ref HuffmanTable acHuffmanTable = ref this.acHuffmanTables[component.ACHuffmanTableId];
+                        ref HuffmanTable dcHuffmanTable = ref this.dcHuffmanTables[component.DcTableId];
+                        ref HuffmanTable acHuffmanTable = ref this.acHuffmanTables[component.AcTableId];
 
                         int h = component.HorizontalSamplingFactor;
                         int v = component.VerticalSamplingFactor;
@@ -233,14 +234,14 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
 
         private void ParseBaselineDataNonInterleaved()
         {
-            JpegComponent component = this.components[this.frame.ComponentOrder[0]];
-            ref HuffmanScanBuffer buffer = ref this.scanBuffer;
+            var component = this.components[this.frame.ComponentOrder[0]] as JpegComponent;
+            ref JpegBitReader buffer = ref this.scanBuffer;
 
             int w = component.WidthInBlocks;
             int h = component.HeightInBlocks;
 
-            ref HuffmanTable dcHuffmanTable = ref this.dcHuffmanTables[component.DCHuffmanTableId];
-            ref HuffmanTable acHuffmanTable = ref this.acHuffmanTables[component.ACHuffmanTableId];
+            ref HuffmanTable dcHuffmanTable = ref this.dcHuffmanTables[component.DcTableId];
+            ref HuffmanTable acHuffmanTable = ref this.acHuffmanTables[component.AcTableId];
 
             for (int j = 0; j < h; j++)
             {
@@ -268,14 +269,14 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
 
         private void ParseBaselineDataSingleComponent()
         {
-            JpegComponent component = this.frame.Components[0];
+            var component = this.frame.Components[0] as JpegComponent;
             int mcuLines = this.frame.McusPerColumn;
             int w = component.WidthInBlocks;
             int h = component.SamplingFactors.Height;
-            ref HuffmanTable dcHuffmanTable = ref this.dcHuffmanTables[component.DCHuffmanTableId];
-            ref HuffmanTable acHuffmanTable = ref this.acHuffmanTables[component.ACHuffmanTableId];
+            ref HuffmanTable dcHuffmanTable = ref this.dcHuffmanTables[component.DcTableId];
+            ref HuffmanTable acHuffmanTable = ref this.acHuffmanTables[component.AcTableId];
 
-            ref HuffmanScanBuffer buffer = ref this.scanBuffer;
+            ref JpegBitReader buffer = ref this.scanBuffer;
 
             for (int i = 0; i < mcuLines; i++)
             {
@@ -382,7 +383,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
             int mcu = 0;
             int mcusPerColumn = this.frame.McusPerColumn;
             int mcusPerLine = this.frame.McusPerLine;
-            ref HuffmanScanBuffer buffer = ref this.scanBuffer;
+            ref JpegBitReader buffer = ref this.scanBuffer;
 
             for (int j = 0; j < mcusPerColumn; j++)
             {
@@ -394,8 +395,8 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
                     for (int k = 0; k < this.scanComponentCount; k++)
                     {
                         int order = this.frame.ComponentOrder[k];
-                        JpegComponent component = this.components[order];
-                        ref HuffmanTable dcHuffmanTable = ref this.dcHuffmanTables[component.DCHuffmanTableId];
+                        var component = this.components[order] as JpegComponent;
+                        ref HuffmanTable dcHuffmanTable = ref this.dcHuffmanTables[component.DcTableId];
 
                         int h = component.HorizontalSamplingFactor;
                         int v = component.VerticalSamplingFactor;
@@ -435,15 +436,15 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
 
         private void ParseProgressiveDataNonInterleaved()
         {
-            JpegComponent component = this.components[this.frame.ComponentOrder[0]];
-            ref HuffmanScanBuffer buffer = ref this.scanBuffer;
+            var component = this.components[this.frame.ComponentOrder[0]] as JpegComponent;
+            ref JpegBitReader buffer = ref this.scanBuffer;
 
             int w = component.WidthInBlocks;
             int h = component.HeightInBlocks;
 
             if (this.SpectralStart == 0)
             {
-                ref HuffmanTable dcHuffmanTable = ref this.dcHuffmanTables[component.DCHuffmanTableId];
+                ref HuffmanTable dcHuffmanTable = ref this.dcHuffmanTables[component.DcTableId];
 
                 for (int j = 0; j < h; j++)
                 {
@@ -470,7 +471,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
             }
             else
             {
-                ref HuffmanTable acHuffmanTable = ref this.acHuffmanTables[component.ACHuffmanTableId];
+                ref HuffmanTable acHuffmanTable = ref this.acHuffmanTables[component.AcTableId];
 
                 for (int j = 0; j < h; j++)
                 {
@@ -503,7 +504,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
             ref HuffmanTable acTable)
         {
             ref short blockDataRef = ref Unsafe.As<Block8x8, short>(ref block);
-            ref HuffmanScanBuffer buffer = ref this.scanBuffer;
+            ref JpegBitReader buffer = ref this.scanBuffer;
 
             // DC
             int t = buffer.DecodeHuffman(ref dcTable);
@@ -545,7 +546,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
         private void DecodeBlockProgressiveDC(JpegComponent component, ref Block8x8 block, ref HuffmanTable dcTable)
         {
             ref short blockDataRef = ref Unsafe.As<Block8x8, short>(ref block);
-            ref HuffmanScanBuffer buffer = ref this.scanBuffer;
+            ref JpegBitReader buffer = ref this.scanBuffer;
 
             if (this.SuccessiveHigh == 0)
             {
@@ -581,7 +582,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
                     return;
                 }
 
-                ref HuffmanScanBuffer buffer = ref this.scanBuffer;
+                ref JpegBitReader buffer = ref this.scanBuffer;
                 int start = this.SpectralStart;
                 int end = this.SpectralEnd;
                 int low = this.SuccessiveLow;
@@ -626,7 +627,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
         private void DecodeBlockProgressiveACRefined(ref short blockDataRef, ref HuffmanTable acTable)
         {
             // Refinement scan for these AC coefficients
-            ref HuffmanScanBuffer buffer = ref this.scanBuffer;
+            ref JpegBitReader buffer = ref this.scanBuffer;
             int start = this.SpectralStart;
             int end = this.SpectralEnd;
 

src/ImageSharp/Formats/Jpeg/Components/Decoder/HuffmanTable.cs

@@ -25,7 +25,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
 
         /// <summary>
         /// Contains the largest code of length k (0 if none). MaxCode[17] is a sentinel to
-        /// ensure <see cref="HuffmanScanBuffer.DecodeHuffman"/> terminates.
+        /// ensure <see cref="JpegBitReader.DecodeHuffman"/> terminates.
         /// </summary>
         public fixed ulong MaxCode[18];
 

src/ImageSharp/Formats/Jpeg/Components/Decoder/IJpegComponent.cs

@@ -10,6 +10,11 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
     /// </summary>
     internal interface IJpegComponent
     {
+        /// <summary>
+        /// Gets the component id.
+        /// </summary>
+        public byte Id { get; }
+
         /// <summary>
         /// Gets the component's position in the components array.
         /// </summary>
@@ -25,6 +30,16 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
         /// </summary>
         Size SamplingFactors { get; }
 
+        /// <summary>
+        /// Gets the horizontal sampling factor.
+        /// </summary>
+        public int HorizontalSamplingFactor { get; }
+
+        /// <summary>
+        /// Gets the vertical sampling factor.
+        /// </summary>
+        public int VerticalSamplingFactor { get; }
+
         /// <summary>
         /// Gets the divisors needed to apply when calculating colors.
         /// <see>
@@ -44,5 +59,38 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
         /// We need to apply IDCT and dequantization to transform them into color-space blocks.
         /// </summary>
         Buffer2D<Block8x8> SpectralBlocks { get; }
+
+        /// <summary>
+        /// Gets or sets DC coefficient predictor.
+        /// </summary>
+        public int DcPredictor { get; set; }
+
+        /// <summary>
+        /// Gets or sets the index for the DC table.
+        /// </summary>
+        public int DcTableId { get; set; }
+
+        /// <summary>
+        /// Gets or sets the index for the AC table.
+        /// </summary>
+        public int AcTableId { get; set; }
+
+        /// <summary>
+        /// Initializes component for future buffers initialization.
+        /// </summary>
+        /// <param name="maxSubFactorH">Maximal horizontal subsampling factor among all the components.</param>
+        /// <param name="maxSubFactorV">Maximal vertical subsampling factor among all the components.</param>
+        public void Init(int maxSubFactorH, int maxSubFactorV);
+
+        /// <summary>
+        /// Allocates the spectral blocks.
+        /// </summary>
+        /// <param name="fullScan">if set to true, use the full height of a block, otherwise use the vertical sampling factor.</param>
+        public void AllocateSpectral(bool fullScan);
+
+        /// <summary>
+        /// Releases resources.
+        /// </summary>
+        public void Dispose();
     }
 }

src/ImageSharp/Formats/Jpeg/Components/Decoder/IJpegScanDecoder.cs

@@ -0,0 +1,49 @@
+// Copyright (c) Six Labors.
+// Licensed under the Apache License, Version 2.0.
+
+namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
+{
+    /// <summary>
+    /// Interface for a JPEG scan decoder.
+    /// </summary>
+    internal interface IJpegScanDecoder
+    {
+        /// <summary>
+        /// Sets the reset interval.
+        /// </summary>
+        int ResetInterval { set; }
+
+        /// <summary>
+        /// Gets or sets the spectral selection start.
+        /// </summary>
+        int SpectralStart { get; set; }
+
+        /// <summary>
+        /// Gets or sets the spectral selection end.
+        /// </summary>
+        int SpectralEnd { get; set; }
+
+        /// <summary>
+        /// Gets or sets the successive approximation high bit end.
+        /// </summary>
+        int SuccessiveHigh { get; set; }
+
+        /// <summary>
+        /// Gets or sets the successive approximation low bit end.
+        /// </summary>
+        int SuccessiveLow { get; set; }
+
+        /// <summary>
+        /// Decodes the entropy coded data.
+        /// </summary>
+        /// <param name="scanComponentCount">Component count in the current scan.</param>
+        void ParseEntropyCodedData(int scanComponentCount);
+
+        /// <summary>
+        /// Sets the JpegFrame and its components and injects the frame data into the spectral converter.
+        /// </summary>
+        /// <param name="frame">The frame.</param>
+        /// <param name="jpegData">The raw JPEG data.</param>
+        void InjectFrameData(JpegFrame frame, IRawJpegData jpegData);
+    }
+}

src/ImageSharp/Formats/Jpeg/Components/Decoder/HuffmanScanBuffer.cs → src/ImageSharp/Formats/Jpeg/Components/Decoder/JpegBitReader.cs

@@ -9,7 +9,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
     /// <summary>
     /// Used to buffer and track the bits read from the Huffman entropy encoded data.
     /// </summary>
-    internal struct HuffmanScanBuffer
+    internal struct JpegBitReader
     {
         private readonly BufferedReadStream stream;
 
@@ -22,7 +22,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
         // Whether there is no more good data to pull from the stream for the current mcu.
         private bool badData;
 
-        public HuffmanScanBuffer(BufferedReadStream stream)
+        public JpegBitReader(BufferedReadStream stream)
         {
             this.stream = stream;
             this.data = 0ul;
@@ -117,7 +117,8 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
         public int Receive(int nbits)
         {
             this.CheckBits();
-            return Extend(this.GetBits(nbits), nbits);
+            int bits = Extend(this.GetBits(nbits), nbits);
+            return bits;
         }
 
         [MethodImpl(InliningOptions.ShortMethod)]

src/ImageSharp/Formats/Jpeg/Components/Decoder/JpegComponent.cs

@@ -9,7 +9,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
     /// <summary>
     /// Represents a single frame component.
     /// </summary>
-    internal sealed class JpegComponent : IDisposable, IJpegComponent
+    internal class JpegComponent : IDisposable, IJpegComponent
     {
         private readonly MemoryAllocator memoryAllocator;
 
@@ -78,12 +78,12 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
         /// <summary>
         /// Gets or sets the index for the DC Huffman table.
         /// </summary>
-        public int DCHuffmanTableId { get; set; }
+        public int DcTableId { get; set; }
 
         /// <summary>
         /// Gets or sets the index for the AC Huffman table.
         /// </summary>
-        public int ACHuffmanTableId { get; set; }
+        public int AcTableId { get; set; }
 
         public JpegFrame Frame { get; }
 
@@ -119,11 +119,12 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
             }
         }
 
+        /// <inheritdoc/>
         public void AllocateSpectral(bool fullScan)
         {
             if (this.SpectralBlocks != null)
             {
-                // this method will be called each scan marker so we need to allocate only once
+                // This method will be called each scan marker so we need to allocate only once.
                 return;
             }
 

src/ImageSharp/Formats/Jpeg/Components/Decoder/JpegComponentPostProcessor.cs

@@ -103,7 +103,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
                     // To be "more accurate", we need to emulate this by rounding!
                     workspaceBlock.NormalizeColorsAndRoundInPlace(maximumValue);
 
-                    // Write to color buffer acording to sampling factors
+                    // Write to color buffer according to sampling factors
                     int xColorBufferStart = xBlock * this.blockAreaSize.Width;
                     workspaceBlock.ScaledCopyTo(
                         ref colorBufferRow[xColorBufferStart],

src/ImageSharp/Formats/Jpeg/Components/Decoder/JpegFrame.cs

@@ -6,14 +6,14 @@ using System;
 namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
 {
     /// <summary>
-    /// Represent a single jpeg frame
+    /// Represent a single jpeg frame.
     /// </summary>
     internal sealed class JpegFrame : IDisposable
     {
         public JpegFrame(JpegFileMarker sofMarker, byte precision, int width, int height, byte componentCount)
         {
-            this.Extended = sofMarker.Marker == JpegConstants.Markers.SOF1;
-            this.Progressive = sofMarker.Marker == JpegConstants.Markers.SOF2;
+            this.Extended = sofMarker.Marker is JpegConstants.Markers.SOF1 or JpegConstants.Markers.SOF9;
+            this.Progressive = sofMarker.Marker is JpegConstants.Markers.SOF2 or JpegConstants.Markers.SOF10;
 
             this.Precision = precision;
             this.MaxColorChannelValue = MathF.Pow(2, precision) - 1;
@@ -65,7 +65,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
         /// <summary>
         /// Gets the pixel size of the image.
         /// </summary>
-        public Size PixelSize => new Size(this.PixelWidth, this.PixelHeight);
+        public Size PixelSize => new(this.PixelWidth, this.PixelHeight);
 
         /// <summary>
         /// Gets the number of components within a frame.
@@ -86,7 +86,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
         /// <summary>
         /// Gets or sets the frame component collection.
         /// </summary>
-        public JpegComponent[] Components { get; set; }
+        public IJpegComponent[] Components { get; set; }
 
         /// <summary>
         /// Gets or sets the number of MCU's per line.
@@ -101,7 +101,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
         /// <summary>
         /// Gets the mcu size of the image.
         /// </summary>
-        public Size McuSize => new Size(this.McusPerLine, this.McusPerColumn);
+        public Size McuSize => new(this.McusPerLine, this.McusPerColumn);
 
         /// <summary>
         /// Gets the color depth, in number of bits per pixel.
@@ -134,7 +134,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
 
             for (int i = 0; i < this.ComponentCount; i++)
             {
-                JpegComponent component = this.Components[i];
+                IJpegComponent component = this.Components[i];
                 component.Init(maxSubFactorH, maxSubFactorV);
             }
         }
@@ -143,7 +143,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
         {
             for (int i = 0; i < this.ComponentCount; i++)
             {
-                JpegComponent component = this.Components[i];
+                IJpegComponent component = this.Components[i];
                 component.AllocateSpectral(fullScan);
             }
         }

src/ImageSharp/Formats/Jpeg/JpegConstants.cs

@@ -306,17 +306,17 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
             public const int RegisterSize = 64;
 
             /// <summary>
-            /// The number of bits to fetch when filling the <see cref="HuffmanScanBuffer"/> buffer.
+            /// The number of bits to fetch when filling the <see cref="JpegBitReader"/> buffer.
             /// </summary>
             public const int FetchBits = 48;
 
             /// <summary>
-            /// The number of times to read the input stream when filling the <see cref="HuffmanScanBuffer"/> buffer.
+            /// The number of times to read the input stream when filling the <see cref="JpegBitReader"/> buffer.
             /// </summary>
             public const int FetchLoop = FetchBits / 8;
 
             /// <summary>
-            /// The minimum number of bits allowed before by the <see cref="HuffmanScanBuffer"/> before fetching.
+            /// The minimum number of bits allowed before by the <see cref="JpegBitReader"/> before fetching.
             /// </summary>
             public const int MinBits = RegisterSize - FetchBits;
 

src/ImageSharp/Formats/Jpeg/JpegDecoderCore.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Buffers;
 using System.Buffers.Binary;
+using System.Collections.Generic;
 using System.IO;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
@@ -97,7 +98,12 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
         /// <summary>
         /// Scan decoder.
         /// </summary>
-        private HuffmanScanDecoder scanDecoder;
+        private IJpegScanDecoder scanDecoder;
+
+        /// <summary>
+        /// The arithmetic decoding tables.
+        /// </summary>
+        private List<ArithmeticDecodingTable> arithmeticDecodingTables;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="JpegDecoderCore" /> class.
@@ -137,7 +143,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
         /// <summary>
         /// Gets the components.
         /// </summary>
-        public JpegComponent[] Components => this.Frame.Components;
+        public IJpegComponent[] Components => this.Frame.Components;
 
         /// <inheritdoc/>
         IJpegComponent[] IRawJpegData.Components => this.Components;
@@ -188,9 +194,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
         {
             using var spectralConverter = new SpectralConverter<TPixel>(this.Configuration);
 
-            var scanDecoder = new HuffmanScanDecoder(stream, spectralConverter, cancellationToken);
-
-            this.ParseStream(stream, scanDecoder, cancellationToken);
+            this.ParseStream(stream, spectralConverter, cancellationToken);
             this.InitExifProfile();
             this.InitIccProfile();
             this.InitIptcProfile();
@@ -206,7 +210,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
         /// <inheritdoc/>
         public IImageInfo Identify(BufferedReadStream stream, CancellationToken cancellationToken)
         {
-            this.ParseStream(stream, scanDecoder: null, cancellationToken);
+            this.ParseStream(stream, spectralConverter: null, cancellationToken);
             this.InitExifProfile();
             this.InitIccProfile();
             this.InitIptcProfile();
@@ -222,12 +226,12 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
         /// so those tables do not need to be duplicated with segmented tiff's (tiff's with multiple strips).
         /// </summary>
         /// <param name="tableBytes">The table bytes.</param>
-        /// <param name="huffmanScanDecoder">The scan decoder.</param>
-        public void LoadTables(byte[] tableBytes, HuffmanScanDecoder huffmanScanDecoder)
+        /// <param name="scanDecoder">The scan decoder.</param>
+        public void LoadTables(byte[] tableBytes, IJpegScanDecoder scanDecoder)
         {
             this.Metadata = new ImageMetadata();
             this.QuantizationTables = new Block8x8F[4];
-            this.scanDecoder = huffmanScanDecoder;
+            this.scanDecoder = scanDecoder;
             using var ms = new MemoryStream(tableBytes);
             using var stream = new BufferedReadStream(this.Configuration, ms);
 
@@ -282,13 +286,11 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
         /// Parses the input stream for file markers.
         /// </summary>
         /// <param name="stream">The input stream.</param>
-        /// <param name="scanDecoder">Scan decoder used exclusively to decode SOS marker.</param>
+        /// <param name="spectralConverter">The spectral converter to use.</param>
         /// <param name="cancellationToken">The token to monitor cancellation.</param>
-        internal void ParseStream(BufferedReadStream stream, HuffmanScanDecoder scanDecoder, CancellationToken cancellationToken)
+        internal void ParseStream(BufferedReadStream stream, SpectralConverter spectralConverter, CancellationToken cancellationToken)
         {
-            bool metadataOnly = scanDecoder == null;
-
-            this.scanDecoder = scanDecoder;
+            bool metadataOnly = spectralConverter == null;
 
             this.Metadata = new ImageMetadata();
 
@@ -322,7 +324,16 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
                         case JpegConstants.Markers.SOF0:
                         case JpegConstants.Markers.SOF1:
                         case JpegConstants.Markers.SOF2:
-                            this.ProcessStartOfFrameMarker(stream, remaining, fileMarker, metadataOnly);
+                            this.scanDecoder = new HuffmanScanDecoder(stream, spectralConverter, cancellationToken);
+                            this.ProcessStartOfFrameMarker(stream, remaining, fileMarker, ComponentType.Huffman, metadataOnly);
+                            break;
+
+                        case JpegConstants.Markers.SOF9:
+                        case JpegConstants.Markers.SOF10:
+                        case JpegConstants.Markers.SOF13:
+                        case JpegConstants.Markers.SOF14:
+                            this.scanDecoder = new ArithmeticScanDecoder(stream, spectralConverter, cancellationToken);
+                            this.ProcessStartOfFrameMarker(stream, remaining, fileMarker, ComponentType.Arithmetic, metadataOnly);
                             break;
 
                         case JpegConstants.Markers.SOF5:
@@ -338,13 +349,9 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
                             JpegThrowHelper.ThrowNotSupportedException("Decoding lossless jpeg files is not supported.");
                             break;
 
-                        case JpegConstants.Markers.SOF9:
-                        case JpegConstants.Markers.SOF10:
                         case JpegConstants.Markers.SOF11:
-                        case JpegConstants.Markers.SOF13:
-                        case JpegConstants.Markers.SOF14:
                         case JpegConstants.Markers.SOF15:
-                            JpegThrowHelper.ThrowNotSupportedException("Decoding jpeg files with arithmetic coding is not supported.");
+                            JpegThrowHelper.ThrowNotSupportedException("Decoding jpeg files with lossless arithmetic coding is not supported.");
                             break;
 
                         case JpegConstants.Markers.SOS:
@@ -428,7 +435,15 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
                             break;
 
                         case JpegConstants.Markers.DAC:
-                            JpegThrowHelper.ThrowNotSupportedException("Decoding jpeg files with arithmetic coding is not supported.");
+                            if (metadataOnly)
+                            {
+                                stream.Skip(remaining);
+                            }
+                            else
+                            {
+                                this.ProcessArithmeticTable(stream, remaining);
+                            }
+
                             break;
                     }
                 }
@@ -856,6 +871,42 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
             }
         }
 
+        private void ProcessArithmeticTable(BufferedReadStream stream, int remaining)
+        {
+            this.arithmeticDecodingTables ??= new List<ArithmeticDecodingTable>(4);
+
+            while (remaining > 0)
+            {
+                int tableClassAndIdentifier = stream.ReadByte();
+                remaining--;
+                byte tableClass = (byte)(tableClassAndIdentifier >> 4);
+                byte identifier = (byte)(tableClassAndIdentifier & 0xF);
+
+                byte conditioningTableValue = (byte)stream.ReadByte();
+                remaining--;
+
+                var arithmeticTable = new ArithmeticDecodingTable(tableClass, identifier);
+                arithmeticTable.Configure(conditioningTableValue);
+
+                bool tableEntryReplaced = false;
+                for (int i = 0; i < this.arithmeticDecodingTables.Count; i++)
+                {
+                    ArithmeticDecodingTable item = this.arithmeticDecodingTables[i];
+                    if (item.TableClass == arithmeticTable.TableClass && item.Identifier == arithmeticTable.Identifier)
+                    {
+                        this.arithmeticDecodingTables[i] = arithmeticTable;
+                        tableEntryReplaced = true;
+                        break;
+                    }
+                }
+
+                if (!tableEntryReplaced)
+                {
+                    this.arithmeticDecodingTables.Add(arithmeticTable);
+                }
+            }
+        }
+
         /// <summary>
         /// Reads the adobe image resource block name: a Pascal string (padded to make size even).
         /// </summary>
@@ -917,7 +968,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
         /// <param name="stream">The input stream.</param>
         /// <param name="remaining">The remaining bytes in the segment block.</param>
         /// <exception cref="ImageFormatException">
-        /// Thrown if the tables do not match the header
+        /// Thrown if the tables do not match the header.
         /// </exception>
         private void ProcessDefineQuantizationTablesMarker(BufferedReadStream stream, int remaining)
         {
@@ -1023,8 +1074,9 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
         /// <param name="stream">The input stream.</param>
         /// <param name="remaining">The remaining bytes in the segment block.</param>
         /// <param name="frameMarker">The current frame marker.</param>
-        /// <param name="metadataOnly">Whether to parse metadata only</param>
-        private void ProcessStartOfFrameMarker(BufferedReadStream stream, int remaining, in JpegFileMarker frameMarker, bool metadataOnly)
+        /// <param name="decodingComponentType">The jpeg decoding component type.</param>
+        /// <param name="metadataOnly">Whether to parse metadata only.</param>
+        private void ProcessStartOfFrameMarker(BufferedReadStream stream, int remaining, in JpegFileMarker frameMarker, ComponentType decodingComponentType, bool metadataOnly)
         {
             if (this.Frame != null)
             {
@@ -1036,17 +1088,21 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
                 JpegThrowHelper.ThrowInvalidImageContentException("Multiple SOF markers. Only single frame jpegs supported.");
             }
 
-            // Read initial marker definitions
+            // Read initial marker definitions.
             const int length = 6;
-            stream.Read(this.temp, 0, length);
+            int bytesRead = stream.Read(this.temp, 0, length);
+            if (bytesRead != length)
+            {
+                JpegThrowHelper.ThrowInvalidImageContentException("SOF marker does not contain enough data.");
+            }
 
-            // 1 byte: Bits/sample precision
+            // 1 byte: Bits/sample precision.
             byte precision = this.temp[0];
 
-            // Validate: only 8-bit and 12-bit precisions are supported
+            // Validate: only 8-bit and 12-bit precisions are supported.
             if (Array.IndexOf(this.supportedPrecisions, precision) == -1)
             {
-                JpegThrowHelper.ThrowInvalidImageContentException("Only 8-Bit and 12-Bit precision supported.");
+                JpegThrowHelper.ThrowInvalidImageContentException("Only 8-Bit and 12-Bit precision is supported.");
             }
 
             // 2 byte: Height
@@ -1055,18 +1111,18 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
             // 2 byte: Width
             int frameWidth = (this.temp[3] << 8) | this.temp[4];
 
-            // Validate: width/height > 0 (they are upper-bounded by 2 byte max value so no need to check that)
+            // Validate: width/height > 0 (they are upper-bounded by 2 byte max value so no need to check that).
             if (frameHeight == 0 || frameWidth == 0)
             {
                 JpegThrowHelper.ThrowInvalidImageDimensions(frameWidth, frameHeight);
             }
 
-            // 1 byte: Number of components
+            // 1 byte: Number of components.
             byte componentCount = this.temp[5];
 
             // Validate: componentCount more than 4 can lead to a buffer overflow during stream
-            // reading so we must limit it to 4
-            // We do not support jpeg images with more than 4 components anyway
+            // reading so we must limit it to 4.
+            // We do not support jpeg images with more than 4 components anyway.
             if (componentCount > 4)
             {
                 JpegThrowHelper.ThrowNotSupportedComponentCount(componentCount);
@@ -1135,7 +1191,9 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
                     JpegThrowHelper.ThrowBadQuantizationTableIndex(quantTableIndex);
                 }
 
-                var component = new JpegComponent(this.Configuration.MemoryAllocator, this.Frame, componentId, h, v, quantTableIndex, i);
+                IJpegComponent component = decodingComponentType is ComponentType.Huffman ?
+                            new JpegComponent(this.Configuration.MemoryAllocator, this.Frame, componentId, h, v, quantTableIndex, i) :
+                            new ArithmeticDecodingComponent(this.Configuration.MemoryAllocator, this.Frame, componentId, h, v, quantTableIndex, i);
 
                 this.Frame.Components[i] = component;
                 this.Frame.ComponentIds[i] = componentId;
@@ -1165,11 +1223,17 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
             const int codeValuesMaxByteSize = 256;
             const int totalBufferSize = codeLengthsByteSize + codeValuesMaxByteSize + HuffmanTable.WorkspaceByteSize;
 
+            var huffmanScanDecoder = this.scanDecoder as HuffmanScanDecoder;
+            if (huffmanScanDecoder is null)
+            {
+                JpegThrowHelper.ThrowInvalidImageContentException("missing huffman table data");
+            }
+
             int length = remaining;
             using (IMemoryOwner<byte> buffer = this.Configuration.MemoryAllocator.Allocate<byte>(totalBufferSize))
             {
                 Span<byte> bufferSpan = buffer.GetSpan();
-                Span<byte> huffmanLegthsSpan = bufferSpan.Slice(0, codeLengthsByteSize);
+                Span<byte> huffmanLengthsSpan = bufferSpan.Slice(0, codeLengthsByteSize);
                 Span<byte> huffmanValuesSpan = bufferSpan.Slice(codeLengthsByteSize, codeValuesMaxByteSize);
                 Span<uint> tableWorkspace = MemoryMarshal.Cast<byte, uint>(bufferSpan.Slice(codeLengthsByteSize + codeValuesMaxByteSize));
 
@@ -1191,12 +1255,12 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
                         JpegThrowHelper.ThrowInvalidImageContentException($"Bad huffman table index: {tableIndex}.");
                     }
 
-                    stream.Read(huffmanLegthsSpan, 1, 16);
+                    stream.Read(huffmanLengthsSpan, 1, 16);
 
                     int codeLengthSum = 0;
                     for (int j = 1; j < 17; j++)
                     {
-                        codeLengthSum += huffmanLegthsSpan[j];
+                        codeLengthSum += huffmanLengthsSpan[j];
                     }
 
                     length -= 17;
@@ -1210,10 +1274,10 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
 
                     i += 17 + codeLengthSum;
 
-                    this.scanDecoder.BuildHuffmanTable(
+                    huffmanScanDecoder!.BuildHuffmanTable(
                         tableType,
                         tableIndex,
-                        huffmanLegthsSpan,
+                        huffmanLengthsSpan,
                         huffmanValuesSpan.Slice(0, codeLengthSum),
                         tableWorkspace);
                 }
@@ -1221,8 +1285,8 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
         }
 
         /// <summary>
-        /// Processes the DRI (Define Restart Interval Marker) Which specifies the interval between RSTn markers, in
-        /// macroblocks
+        /// Processes the DRI (Define Restart Interval Marker) Which specifies the interval between RSTn markers,
+        /// in macroblocks.
         /// </summary>
         /// <param name="stream">The input stream.</param>
         /// <param name="remaining">The remaining bytes in the segment block.</param>
@@ -1246,7 +1310,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
                 JpegThrowHelper.ThrowInvalidImageContentException("No readable SOFn (Start Of Frame) marker found.");
             }
 
-            // 1 byte: Number of components in scan
+            // 1 byte: Number of components in scan.
             int selectorsCount = stream.ReadByte();
 
             // Validate: 0 < count <= totalComponents
@@ -1256,7 +1320,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
                 JpegThrowHelper.ThrowInvalidImageContentException($"Invalid number of components in scan: {selectorsCount}.");
             }
 
-            // Validate: marker must contain exactly (4 + selectorsCount*2) bytes
+            // Validate: Marker must contain exactly (4 + selectorsCount*2) bytes
             int selectorsBytes = selectorsCount * 2;
             if (remaining != 4 + selectorsBytes)
             {
@@ -1283,7 +1347,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
                     }
                 }
 
-                // Validate: must be found among registered components
+                // Validate: Must be found among registered components.
                 if (componentIndex == -1)
                 {
                     // TODO: extract as separate method?
@@ -1292,7 +1356,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
 
                 this.Frame.ComponentOrder[i / 2] = (byte)componentIndex;
 
-                JpegComponent component = this.Frame.Components[componentIndex];
+                IJpegComponent component = this.Frame.Components[componentIndex];
 
                 // 1 byte: Huffman table selectors.
                 // 4 bits - dc
@@ -1308,8 +1372,8 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
                     JpegThrowHelper.ThrowInvalidImageContentException($"Invalid huffman table for component:{componentSelectorId}: dc={dcTableIndex}, ac={acTableIndex}");
                 }
 
-                component.DCHuffmanTableId = dcTableIndex;
-                component.ACHuffmanTableId = acTableIndex;
+                component.DcTableId = dcTableIndex;
+                component.AcTableId = acTableIndex;
             }
 
             // 3 bytes: Progressive scan decoding data
@@ -1325,18 +1389,28 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
             this.scanDecoder.SuccessiveHigh = successiveApproximation >> 4;
             this.scanDecoder.SuccessiveLow = successiveApproximation & 15;
 
+            if (this.scanDecoder is ArithmeticScanDecoder arithmeticScanDecoder)
+            {
+                arithmeticScanDecoder.InitDecodingTables(this.arithmeticDecodingTables);
+            }
+
             this.scanDecoder.ParseEntropyCodedData(selectorsCount);
         }
 
         /// <summary>
-        /// Reads a <see cref="ushort"/> from the stream advancing it by two bytes
+        /// Reads a <see cref="ushort"/> from the stream advancing it by two bytes.
         /// </summary>
         /// <param name="stream">The input stream.</param>
         /// <returns>The <see cref="ushort"/></returns>
         [MethodImpl(InliningOptions.ShortMethod)]
         private ushort ReadUint16(BufferedReadStream stream)
         {
-            stream.Read(this.markerBuffer, 0, 2);
+            int bytesRead = stream.Read(this.markerBuffer, 0, 2);
+            if (bytesRead != 2)
+            {
+                JpegThrowHelper.ThrowInvalidImageContentException("stream does not contain enough data, could not read ushort.");
+            }
+
             return BinaryPrimitives.ReadUInt16BigEndian(this.markerBuffer);
         }
     }

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

@@ -62,7 +62,7 @@ namespace SixLabors.ImageSharp.Formats.Tiff.Compression.Decompressors
                         using SpectralConverter<L8> spectralConverterGray = new GrayJpegSpectralConverter<L8>(this.configuration);
                         var scanDecoderGray = new HuffmanScanDecoder(stream, spectralConverterGray, CancellationToken.None);
                         jpegDecoder.LoadTables(this.jpegTables, scanDecoderGray);
-                        jpegDecoder.ParseStream(stream, scanDecoderGray, CancellationToken.None);
+                        jpegDecoder.ParseStream(stream, spectralConverterGray, CancellationToken.None);
 
                         // TODO: Should we pass through the CancellationToken from the tiff decoder?
                         CopyImageBytesToBuffer(buffer, spectralConverterGray.GetPixelBuffer(CancellationToken.None));
@@ -78,7 +78,7 @@ namespace SixLabors.ImageSharp.Formats.Tiff.Compression.Decompressors
                             new RgbJpegSpectralConverter<Rgb24>(this.configuration) : new SpectralConverter<Rgb24>(this.configuration);
                         var scanDecoder = new HuffmanScanDecoder(stream, spectralConverter, CancellationToken.None);
                         jpegDecoder.LoadTables(this.jpegTables, scanDecoder);
-                        jpegDecoder.ParseStream(stream, scanDecoder, CancellationToken.None);
+                        jpegDecoder.ParseStream(stream, spectralConverter, CancellationToken.None);
 
                         // TODO: Should we pass through the CancellationToken from the tiff decoder?
                         CopyImageBytesToBuffer(buffer, spectralConverter.GetPixelBuffer(CancellationToken.None));

tests/ImageSharp.Benchmarks/Codecs/Jpeg/DecodeJpegParseStreamOnly.cs

@@ -40,8 +40,8 @@ namespace SixLabors.ImageSharp.Benchmarks.Codecs.Jpeg
             using var bufferedStream = new BufferedReadStream(Configuration.Default, memoryStream);
 
             using var decoder = new JpegDecoderCore(Configuration.Default, new JpegDecoder { IgnoreMetadata = true });
-            var scanDecoder = new HuffmanScanDecoder(bufferedStream, new NoopSpectralConverter(), cancellationToken: default);
-            decoder.ParseStream(bufferedStream, scanDecoder, cancellationToken: default);
+            var spectralConverter = new NoopSpectralConverter();
+            decoder.ParseStream(bufferedStream, spectralConverter, cancellationToken: default);
         }
 
         // We want to test only stream parsing and scan decoding, we don't need to convert spectral data to actual pixels

tests/ImageSharp.Benchmarks/LoadResizeSave/LoadResizeSaveStressRunner.cs

@@ -10,12 +10,10 @@ using System.IO;
 using System.Linq;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
-using System.Threading;
 using System.Threading.Tasks;
 using ImageMagick;
 using PhotoSauce.MagicScaler;
 using SixLabors.ImageSharp.Formats.Jpeg;
-using SixLabors.ImageSharp.Memory;
 using SixLabors.ImageSharp.Processing;
 using SixLabors.ImageSharp.Tests;
 using SkiaSharp;
@@ -228,8 +226,9 @@ namespace SixLabors.ImageSharp.Benchmarks.LoadResizeSave
         public async Task ImageSharpResizeAsync(string input)
         {
             using FileStream output = File.Open(this.OutputPath(input), FileMode.Create);
-            // Resize it to fit a 150x150 square
-            using var image = await ImageSharpImage.LoadAsync(input);
+
+            // Resize it to fit a 150x150 square.
+            using ImageSharpImage image = await ImageSharpImage.LoadAsync(input);
             this.LogImageProcessed(image.Width, image.Height);
 
             image.Mutate(i => i.Resize(new ResizeOptions

tests/ImageSharp.Tests.ProfilingSandbox/LoadResizeSaveParallelMemoryStress.cs

@@ -5,7 +5,6 @@ using System;
 using System.Diagnostics;
 using System.Globalization;
 using System.IO;
-using System.Runtime.CompilerServices;
 using System.Text;
 using System.Threading;
 using CommandLine;
@@ -68,7 +67,6 @@ namespace SixLabors.ImageSharp.Tests.ProfilingSandbox
                 lrs.leakFrequency = options.LeakFrequency;
                 lrs.gcFrequency = options.GcFrequency;
 
-
                 timer = Stopwatch.StartNew();
                 try
                 {

tests/ImageSharp.Tests/Formats/Jpg/ParseStreamTests.cs

@@ -50,7 +50,7 @@ namespace SixLabors.ImageSharp.Tests.Formats.Jpg
                 Assert.Equal(expectedSizeInBlocks, decoder.Frame.McuSize);
 
                 var uniform1 = new Size(1, 1);
-                JpegComponent c0 = decoder.Components[0];
+                IJpegComponent c0 = decoder.Components[0];
                 VerifyJpeg.VerifyComponent(c0, expectedSizeInBlocks, uniform1, uniform1);
             }
         }
@@ -70,8 +70,8 @@ namespace SixLabors.ImageSharp.Tests.Formats.Jpg
             {
                 sb.AppendLine(imageFile);
                 sb.AppendLine($"Size:{decoder.Frame.PixelSize} MCU:{decoder.Frame.McuSize}");
-                JpegComponent c0 = decoder.Components[0];
-                JpegComponent c1 = decoder.Components[1];
+                IJpegComponent c0 = decoder.Components[0];
+                IJpegComponent c1 = decoder.Components[1];
 
                 sb.AppendLine($"Luma: SAMP: {c0.SamplingFactors} BLOCKS: {c0.SizeInBlocks}");
                 sb.AppendLine($"Chroma: {c1.SamplingFactors} BLOCKS: {c1.SizeInBlocks}");
@@ -80,17 +80,17 @@ namespace SixLabors.ImageSharp.Tests.Formats.Jpg
             this.Output.WriteLine(sb.ToString());
         }
 
-        public static readonly TheoryData<string, int, object, object> ComponentVerificationData = new TheoryData<string, int, object, object>
-            {
-                { TestImages.Jpeg.Baseline.Jpeg444, 3, new Size(1, 1), new Size(1, 1) },
-                { TestImages.Jpeg.Baseline.Jpeg420Exif, 3, new Size(2, 2), new Size(1, 1) },
-                { TestImages.Jpeg.Baseline.Jpeg420Small, 3, new Size(2, 2), new Size(1, 1) },
-                { TestImages.Jpeg.Baseline.Testorig420, 3, new Size(2, 2), new Size(1, 1) },
+        public static readonly TheoryData<string, int, object, object> ComponentVerificationData = new()
+        {
+            { TestImages.Jpeg.Baseline.Jpeg444, 3, new Size(1, 1), new Size(1, 1) },
+            { TestImages.Jpeg.Baseline.Jpeg420Exif, 3, new Size(2, 2), new Size(1, 1) },
+            { TestImages.Jpeg.Baseline.Jpeg420Small, 3, new Size(2, 2), new Size(1, 1) },
+            { TestImages.Jpeg.Baseline.Testorig420, 3, new Size(2, 2), new Size(1, 1) },
 
-                // TODO: Find Ycck or Cmyk images with different subsampling
-                { TestImages.Jpeg.Baseline.Ycck, 4, new Size(1, 1), new Size(1, 1) },
-                { TestImages.Jpeg.Baseline.Cmyk, 4, new Size(1, 1), new Size(1, 1) },
-            };
+            // TODO: Find Ycck or Cmyk images with different subsampling
+            { TestImages.Jpeg.Baseline.Ycck, 4, new Size(1, 1), new Size(1, 1) },
+            { TestImages.Jpeg.Baseline.Cmyk, 4, new Size(1, 1), new Size(1, 1) },
+        };
 
         [Theory]
         [MemberData(nameof(ComponentVerificationData))]
@@ -108,9 +108,9 @@ namespace SixLabors.ImageSharp.Tests.Formats.Jpg
                 Assert.Equal(componentCount, decoder.Frame.ComponentCount);
                 Assert.Equal(componentCount, decoder.Components.Length);
 
-                JpegComponent c0 = decoder.Components[0];
-                JpegComponent c1 = decoder.Components[1];
-                JpegComponent c2 = decoder.Components[2];
+                IJpegComponent c0 = decoder.Components[0];
+                IJpegComponent c1 = decoder.Components[1];
+                IJpegComponent c2 = decoder.Components[2];
 
                 var uniform1 = new Size(1, 1);
 
@@ -126,7 +126,7 @@ namespace SixLabors.ImageSharp.Tests.Formats.Jpg
 
                 if (componentCount == 4)
                 {
-                    JpegComponent c3 = decoder.Components[2];
+                    IJpegComponent c3 = decoder.Components[2];
                     VerifyJpeg.VerifyComponent(c3, expectedLumaSizeInBlocks, fLuma, uniform1);
                 }
             }

tests/ImageSharp.Tests/Formats/Jpg/SpectralJpegTests.cs

@@ -59,7 +59,7 @@ namespace SixLabors.ImageSharp.Tests.Formats.Jpg
             var scanDecoder = new HuffmanScanDecoder(bufferedStream, debugConverter, cancellationToken: default);
 
             // This would parse entire image
-            decoder.ParseStream(bufferedStream, scanDecoder, cancellationToken: default);
+            decoder.ParseStream(bufferedStream, debugConverter, cancellationToken: default);
             VerifyJpeg.SaveSpectralImage(provider, debugConverter.SpectralData);
         }
 
@@ -88,7 +88,7 @@ namespace SixLabors.ImageSharp.Tests.Formats.Jpg
             var scanDecoder = new HuffmanScanDecoder(bufferedStream, debugConverter, cancellationToken: default);
 
             // This would parse entire image
-            decoder.ParseStream(bufferedStream, scanDecoder, cancellationToken: default);
+            decoder.ParseStream(bufferedStream, debugConverter, cancellationToken: default);
 
             // Actual verification
             this.VerifySpectralCorrectnessImpl(libJpegData, debugConverter.SpectralData);
@@ -195,7 +195,7 @@ namespace SixLabors.ImageSharp.Tests.Formats.Jpg
                 var spectralComponents = new LibJpegTools.ComponentData[frame.ComponentCount];
                 for (int i = 0; i < spectralComponents.Length; i++)
                 {
-                    JpegComponent component = frame.Components[i];
+                    var component = frame.Components[i] as JpegComponent;
                     spectralComponents[i] = new LibJpegTools.ComponentData(component.WidthInBlocks, component.HeightInBlocks, component.Index);
                 }
 

tests/ImageSharp.Tests/Formats/Jpg/SpectralToPixelConversionTests.cs

@@ -2,7 +2,6 @@
 // Licensed under the Apache License, Version 2.0.
 
 using System.IO;
-using System.Linq;
 using System.Threading;
 using SixLabors.ImageSharp.Formats.Jpeg;
 using SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder;
@@ -26,10 +25,7 @@ namespace SixLabors.ImageSharp.Tests.Formats.Jpg
                 TestImages.Jpeg.Baseline.MultiScanBaselineCMYK
             };
 
-        public SpectralToPixelConversionTests(ITestOutputHelper output)
-        {
-            this.Output = output;
-        }
+        public SpectralToPixelConversionTests(ITestOutputHelper output) => this.Output = output;
 
         private ITestOutputHelper Output { get; }
 
@@ -47,14 +43,14 @@ namespace SixLabors.ImageSharp.Tests.Formats.Jpg
             using var converter = new SpectralConverter<TPixel>(Configuration.Default);
             using var decoder = new JpegDecoderCore(Configuration.Default, new JpegDecoder());
             var scanDecoder = new HuffmanScanDecoder(bufferedStream, converter, cancellationToken: default);
-            decoder.ParseStream(bufferedStream, scanDecoder, cancellationToken: default);
+            decoder.ParseStream(bufferedStream, converter, cancellationToken: default);
 
             // Test metadata
             provider.Utility.TestGroupName = nameof(JpegDecoderTests);
             provider.Utility.TestName = JpegDecoderTests.DecodeBaselineJpegOutputName;
 
             // Comparison
-            using (Image<TPixel> image = new Image<TPixel>(Configuration.Default, converter.GetPixelBuffer(CancellationToken.None), new ImageMetadata()))
+            using (var image = new Image<TPixel>(Configuration.Default, converter.GetPixelBuffer(CancellationToken.None), new ImageMetadata()))
             using (Image<TPixel> referenceImage = provider.GetReferenceOutputImage<TPixel>(appendPixelTypeToFileName: false))
             {
                 ImageSimilarityReport report = ImageComparer.Exact.CompareImagesOrFrames(referenceImage, image);

tests/ImageSharp.Tests/Formats/Jpg/Utils/LibJpegTools.ComponentData.cs

@@ -26,11 +26,13 @@ namespace SixLabors.ImageSharp.Tests.Formats.Jpg.Utils
                 this.SpectralBlocks = Configuration.Default.MemoryAllocator.Allocate2D<Block8x8>(this.WidthInBlocks, this.HeightInBlocks);
             }
 
-            public Size Size => new Size(this.WidthInBlocks, this.HeightInBlocks);
+            public byte Id { get; }
+
+            public Size Size => new(this.WidthInBlocks, this.HeightInBlocks);
 
             public int Index { get; }
 
-            public Size SizeInBlocks => new Size(this.WidthInBlocks, this.HeightInBlocks);
+            public Size SizeInBlocks => new(this.WidthInBlocks, this.HeightInBlocks);
 
             public Size SamplingFactors => throw new NotSupportedException();
 
@@ -48,6 +50,16 @@ namespace SixLabors.ImageSharp.Tests.Formats.Jpg.Utils
 
             public short MaxVal { get; private set; } = short.MinValue;
 
+            public int HorizontalSamplingFactor => throw new NotImplementedException();
+
+            public int VerticalSamplingFactor => throw new NotImplementedException();
+
+            public int DcPredictor { get; set; }
+
+            public int DcTableId { get; set; }
+
+            public int AcTableId { get; set; }
+
             internal void MakeBlock(Block8x8 block, int y, int x)
             {
                 block.TransposeInplace();
@@ -77,7 +89,7 @@ namespace SixLabors.ImageSharp.Tests.Formats.Jpg.Utils
                 }
             }
 
-            public void LoadSpectral(JpegComponent c)
+            public void LoadSpectral(IJpegComponent c)
             {
                 Buffer2D<Block8x8> data = c.SpectralBlocks;
                 for (int y = 0; y < this.HeightInBlocks; y++)
@@ -201,25 +213,19 @@ namespace SixLabors.ImageSharp.Tests.Formats.Jpg.Utils
                 return this.Equals((ComponentData)obj);
             }
 
-            public override int GetHashCode()
-            {
-                return HashCode.Combine(this.Index, this.HeightInBlocks, this.WidthInBlocks, this.MinVal, this.MaxVal);
-            }
+            public override int GetHashCode() => HashCode.Combine(this.Index, this.HeightInBlocks, this.WidthInBlocks, this.MinVal, this.MaxVal);
 
-            public ref Block8x8 GetBlockReference(int column, int row)
-            {
-                throw new NotImplementedException();
-            }
+            public ref Block8x8 GetBlockReference(int column, int row) => throw new NotImplementedException();
 
-            public static bool operator ==(ComponentData left, ComponentData right)
-            {
-                return object.Equals(left, right);
-            }
+            public void Init(int maxSubFactorH, int maxSubFactorV) => throw new NotImplementedException();
 
-            public static bool operator !=(ComponentData left, ComponentData right)
-            {
-                return !object.Equals(left, right);
-            }
+            public void AllocateSpectral(bool fullScan) => throw new NotImplementedException();
+
+            public void Dispose() => throw new NotImplementedException();
+
+            public static bool operator ==(ComponentData left, ComponentData right) => Equals(left, right);
+
+            public static bool operator !=(ComponentData left, ComponentData right) => !Equals(left, right);
         }
     }
 }

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

@@ -273,7 +273,7 @@ namespace SixLabors.ImageSharp.Tests.Formats.Tiff
 
         [Theory]
         [WithFile(Rgba6BitAssociatedAlpha, PixelTypes.Rgba32)]
-        public void TiffDecoder_CanDecode_24Bit_WithAssociatedAlpha<TPixel>(TestImageProvider<TPixel> provider)            
+        public void TiffDecoder_CanDecode_24Bit_WithAssociatedAlpha<TPixel>(TestImageProvider<TPixel> provider)
             where TPixel : unmanaged, IPixel<TPixel>
         {
             if (TestEnvironment.IsOSX)

tests/ImageSharp.Tests/Image/ImageTests.Decode_Cancellation.cs

@@ -124,7 +124,7 @@ namespace SixLabors.ImageSharp.Tests
                 this.continueSemaphore.Release();
             }
 
-            protected override Stream CreateStream() => this.TestFormat.CreateAsyncSamaphoreStream(this.notifyWaitPositionReachedSemaphore, this.continueSemaphore, this.isTestStreamSeekable);
+            protected override Stream CreateStream() => this.TestFormat.CreateAsyncSemaphoreStream(this.notifyWaitPositionReachedSemaphore, this.continueSemaphore, this.isTestStreamSeekable);
         }
     }
 }

tests/ImageSharp.Tests/TestFormat.cs

@@ -24,7 +24,7 @@ namespace SixLabors.ImageSharp.Tests
 
         // We should not change Configuration.Default in individual tests!
         // Create new configuration instances with new Configuration(TestFormat.GlobalTestFormat) instead!
-        public static TestFormat GlobalTestFormat { get; } = new TestFormat();
+        public static TestFormat GlobalTestFormat { get; } = new();
 
         public TestFormat()
         {
@@ -32,7 +32,7 @@ namespace SixLabors.ImageSharp.Tests
             this.Decoder = new TestDecoder(this);
         }
 
-        public List<DecodeOperation> DecodeCalls { get; } = new List<DecodeOperation>();
+        public List<DecodeOperation> DecodeCalls { get; } = new();
 
         public TestEncoder Encoder { get; }
 
@@ -54,12 +54,12 @@ namespace SixLabors.ImageSharp.Tests
             return ms;
         }
 
-        public Stream CreateAsyncSamaphoreStream(SemaphoreSlim notifyWaitPositionReachedSemaphore, SemaphoreSlim continueSemaphore, bool seeakable, int size = 1024, int waitAfterPosition = 512)
+        public Stream CreateAsyncSemaphoreStream(SemaphoreSlim notifyWaitPositionReachedSemaphore, SemaphoreSlim continueSemaphore, bool seeakable, int size = 1024, int waitAfterPosition = 512)
         {
             var buffer = new byte[size];
             this.header.CopyTo(buffer, 0);
             var semaphoreStream = new SemaphoreReadMemoryStream(buffer, waitAfterPosition, notifyWaitPositionReachedSemaphore, continueSemaphore);
-            return seeakable ? (Stream)semaphoreStream : new AsyncStreamWrapper(semaphoreStream, () => false);
+            return seeakable ? semaphoreStream : new AsyncStreamWrapper(semaphoreStream, () => false);
         }
 
         public void VerifySpecificDecodeCall<TPixel>(byte[] marker, Configuration config)
@@ -191,20 +191,14 @@ namespace SixLabors.ImageSharp.Tests
                 return null;
             }
 
-            public TestHeader(TestFormat testFormat)
-            {
-                this.testFormat = testFormat;
-            }
+            public TestHeader(TestFormat testFormat) => this.testFormat = testFormat;
         }
 
         public class TestDecoder : IImageDecoder, IImageInfoDetector
         {
             private readonly TestFormat testFormat;
 
-            public TestDecoder(TestFormat testFormat)
-            {
-                this.testFormat = testFormat;
-            }
+            public TestDecoder(TestFormat testFormat) => this.testFormat = testFormat;
 
             public IEnumerable<string> MimeTypes => new[] { this.testFormat.MimeType };
 
@@ -216,7 +210,6 @@ namespace SixLabors.ImageSharp.Tests
                 where TPixel : unmanaged, IPixel<TPixel>
                 => this.DecodeImpl<TPixel>(configuration, stream);
 
-
             private Image<TPixel> DecodeImpl<TPixel>(Configuration config, Stream stream)
                 where TPixel : unmanaged, IPixel<TPixel>
             {
@@ -246,10 +239,7 @@ namespace SixLabors.ImageSharp.Tests
         {
             private readonly TestFormat testFormat;
 
-            public TestEncoder(TestFormat testFormat)
-            {
-                this.testFormat = testFormat;
-            }
+            public TestEncoder(TestFormat testFormat) => this.testFormat = testFormat;
 
             public IEnumerable<string> MimeTypes => new[] { this.testFormat.MimeType };
 
@@ -262,16 +252,12 @@ namespace SixLabors.ImageSharp.Tests
             }
 
             public Task EncodeAsync<TPixel>(Image<TPixel> image, Stream stream, CancellationToken cancellationToken)
-               where TPixel : unmanaged, IPixel<TPixel>
-            {
-                // TODO record this happened so we can verify it.
-                return Task.CompletedTask;
-            }
+               where TPixel : unmanaged, IPixel<TPixel> => Task.CompletedTask;  // TODO record this happened so we can verify it.
         }
 
         public struct TestPixelForAgnosticDecode : IPixel<TestPixelForAgnosticDecode>
         {
-            public PixelOperations<TestPixelForAgnosticDecode> CreatePixelOperations() => new PixelOperations<TestPixelForAgnosticDecode>();
+            public PixelOperations<TestPixelForAgnosticDecode> CreatePixelOperations() => new();
 
             public void FromScaledVector4(Vector4 vector)
             {