Implemented quantization tables

src/ImageSharp/Formats/Jpeg/Components/Block8x8.Intrinsic.cs

@@ -7,7 +7,7 @@ using System.Runtime.Intrinsics;
 
 namespace SixLabors.ImageSharp.Formats.Jpeg.Components
 {
-    internal unsafe partial struct Block8x8
+    public unsafe partial struct Block8x8
     {
         [FieldOffset(0)]
         public Vector128<short> V0;

src/ImageSharp/Formats/Jpeg/Components/Block8x8.cs

@@ -18,7 +18,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components
     /// </summary>
     // ReSharper disable once InconsistentNaming
     [StructLayout(LayoutKind.Explicit)]
-    internal unsafe partial struct Block8x8
+    public unsafe partial struct Block8x8
     {
         /// <summary>
         /// A number of scalar coefficients in a <see cref="Block8x8F"/>
@@ -122,6 +122,21 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components
             }
         }
 
+        public static Block8x8 Load(ReadOnlySpan<byte> data)
+        {
+            Unsafe.SkipInit(out Block8x8 result);
+            result.LoadFrom(data);
+            return result;
+        }
+
+        public void LoadFrom(ReadOnlySpan<byte> source)
+        {
+            for (int i = 0; i < Size; i++)
+            {
+                this[i] = source[i];
+            }
+        }
+
         /// <summary>
         /// Load raw 16bit integers from source.
         /// </summary>

src/ImageSharp/Formats/Jpeg/Components/Block8x8F.Generated.cs

@@ -8,7 +8,7 @@ using System.Runtime.CompilerServices;
 // <auto-generated />
 namespace SixLabors.ImageSharp.Formats.Jpeg.Components
 {
-	internal partial struct Block8x8F
+    public partial struct Block8x8F
     {
 		/// <summary>
         /// Level shift by +maximum/2, clip to [0, maximum]

src/ImageSharp/Formats/Jpeg/Components/Block8x8F.Intrinsic.cs

@@ -11,7 +11,7 @@ using System.Runtime.Intrinsics.X86;
 
 namespace SixLabors.ImageSharp.Formats.Jpeg.Components
 {
-    internal partial struct Block8x8F
+    public partial struct Block8x8F
     {
         /// <summary>
         /// A number of rows of 8 scalar coefficients each in <see cref="Block8x8F"/>

src/ImageSharp/Formats/Jpeg/Components/Block8x8F.ScaledCopyTo.cs

@@ -10,7 +10,7 @@ using SixLabors.ImageSharp.Memory;
 // ReSharper disable InconsistentNaming
 namespace SixLabors.ImageSharp.Formats.Jpeg.Components
 {
-    internal partial struct Block8x8F
+    public partial struct Block8x8F
     {
         /// <summary>
         /// Copy block data into the destination color buffer pixel area with the provided horizontal and vertical scale factors.

src/ImageSharp/Formats/Jpeg/Components/Block8x8F.cs

@@ -18,7 +18,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components
     /// 8x8 matrix of <see cref="float"/> coefficients.
     /// </summary>
     [StructLayout(LayoutKind.Explicit)]
-    internal partial struct Block8x8F : IEquatable<Block8x8F>
+    public partial struct Block8x8F : IEquatable<Block8x8F>
     {
         /// <summary>
         /// A number of scalar coefficients in a <see cref="Block8x8F"/>

src/ImageSharp/Formats/Jpeg/Components/Encoder/HuffmanScanEncoder.cs

@@ -62,12 +62,12 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Encoder
         /// <summary>
         /// The DC Huffman tables.
         /// </summary>
-        private readonly HuffmanLut[] dcHuffmanTables;
+        private readonly HuffmanLut[] dcHuffmanTables = new HuffmanLut[4];
 
         /// <summary>
         /// The AC Huffman tables.
         /// </summary>
-        private readonly HuffmanLut[] acHuffmanTables;
+        private readonly HuffmanLut[] acHuffmanTables = new HuffmanLut[4];
 
         /// <summary>
         /// Emitted bits 'micro buffer' before being transferred to the <see cref="emitBuffer"/>.
@@ -119,9 +119,6 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Encoder
             this.streamWriteBuffer = new byte[emitBufferByteLength * OutputBufferLengthMultiplier];
 
             this.target = outputStream;
-
-            this.dcHuffmanTables = new HuffmanLut[4];
-            this.acHuffmanTables = new HuffmanLut[4];
         }
 
         /// <summary>
@@ -135,10 +132,10 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Encoder
             get => this.emitWriteIndex < (uint)this.emitBuffer.Length / 2;
         }
 
-        public void BuildHuffmanTable(JpegHuffmanTableConfig table)
+        public void BuildHuffmanTable(JpegHuffmanTableConfig tableConfig)
         {
-            HuffmanLut[] tables = table.Class == 0 ? this.dcHuffmanTables : this.acHuffmanTables;
-            tables[table.DestinationIndex] = new HuffmanLut(table.TableSpec);
+            HuffmanLut[] tables = tableConfig.Class == 0 ? this.dcHuffmanTables : this.acHuffmanTables;
+            tables[tableConfig.DestinationIndex] = new HuffmanLut(tableConfig.Table);
         }
 
         public void EncodeInterleavedScan<TPixel>(JpegFrame frame, Image<TPixel> image, Block8x8F[] quantTables, Configuration configuration, CancellationToken cancellationToken)

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

@@ -176,7 +176,19 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components
             return quality < 50 ? (5000 / quality) : (200 - (quality * 2));
         }
 
-        private static Block8x8F ScaleQuantizationTable(int scale, ReadOnlySpan<byte> unscaledTable)
+        public static Block8x8F ScaleQuantizationTable(int scale, ReadOnlySpan<byte> unscaledTable)
+        {
+            Block8x8F table = default;
+            for (int j = 0; j < Block8x8F.Size; j++)
+            {
+                int x = ((unscaledTable[j] * scale) + 50) / 100;
+                table[j] = Numerics.Clamp(x, 1, 255);
+            }
+
+            return table;
+        }
+
+        public static Block8x8F ScaleQuantizationTable(int scale, Block8x8 unscaledTable)
         {
             Block8x8F table = default;
             for (int j = 0; j < Block8x8F.Size; j++)

src/ImageSharp/Formats/Jpeg/JpegEncoder.cs

@@ -5,6 +5,7 @@ using System;
 using System.IO;
 using System.Threading;
 using System.Threading.Tasks;
+using SixLabors.ImageSharp.Formats.Jpeg.Components;
 using SixLabors.ImageSharp.Formats.Jpeg.Components.Encoder;
 using SixLabors.ImageSharp.PixelFormats;
 
@@ -125,11 +126,20 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
 
         public int DestinationIndex { get; set; }
 
-        public HuffmanSpec TableSpec { get; set; }
+        public HuffmanSpec Table { get; set; }
+    }
+
+    public class JpegQuantizationTableConfig
+    {
+        public int DestinationIndex { get; set; }
+
+        public Block8x8 Table { get; set; }
     }
 
     public class JpegScanConfig
     {
         public JpegHuffmanTableConfig[] HuffmanTables { get; set; }
+
+        public JpegQuantizationTableConfig[] QuantizationTables { get; set; }
     }
 }

src/ImageSharp/Formats/Jpeg/JpegEncoderCore.cs

@@ -50,6 +50,8 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
 
         private HuffmanScanEncoder scanEncoder;
 
+        public Block8x8F[] QuantizationTables { get; } = new Block8x8F[4];
+
         /// <summary>
         /// The output stream. All attempted writes after the first error become no-ops.
         /// </summary>
@@ -95,10 +97,6 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
             ImageMetadata metadata = image.Metadata;
             JpegMetadata jpegMetadata = metadata.GetJpegMetadata();
 
-            // TODO: Right now encoder writes both quantization tables for grayscale images - we shouldn't do that
-            // Initialize the quantization tables.
-            this.InitQuantizationTables(this.frameConfig.Components.Length, jpegMetadata, out Block8x8F luminanceQuantTable, out Block8x8F chrominanceQuantTable);
-
             // Write the Start Of Image marker.
             this.WriteStartOfImage();
 
@@ -117,21 +115,20 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
                 this.WriteApp14Marker();
             }
 
-            // Write the quantization tables.
-            this.WriteDefineQuantizationTables(ref luminanceQuantTable, ref chrominanceQuantTable);
-
             // Write the image dimensions.
             this.WriteStartOfFrame(image.Width, image.Height, this.frameConfig);
 
             // Write the Huffman tables.
             this.WriteDefineHuffmanTables(this.scanConfig.HuffmanTables);
 
+            // Write the quantization tables.
+            this.InitQuantizationTables(this.scanConfig.QuantizationTables, jpegMetadata);
+
             // Write the scan header.
             this.WriteStartOfScan(this.frameConfig.Components.Length, this.frameConfig.Components);
 
             var frame = new Components.Encoder.JpegFrame(this.frameConfig, Configuration.Default.MemoryAllocator, image, GetTargetColorSpace(this.frameConfig.ColorType));
-            var quantTables = new Block8x8F[] { luminanceQuantTable, chrominanceQuantTable };
-            this.scanEncoder.EncodeInterleavedScan(frame, image, quantTables, Configuration.Default, cancellationToken);
+            this.scanEncoder.EncodeInterleavedScan(frame, image, this.QuantizationTables, Configuration.Default, cancellationToken);
 
             // Write the End Of Image marker.
             this.WriteEndOfImageMarker();
@@ -281,26 +278,26 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
         /// Writes the Define Huffman Table marker and tables.
         /// </summary>
         /// <param name="componentCount">The number of components to write.</param>
-        private void WriteDefineHuffmanTables(JpegHuffmanTableConfig[] tables)
+        private void WriteDefineHuffmanTables(JpegHuffmanTableConfig[] tableConfigs)
         {
             int markerlen = 2;
 
-            for (int i = 0; i < tables.Length; i++)
+            for (int i = 0; i < tableConfigs.Length; i++)
             {
-                markerlen += 1 + 16 + tables[i].TableSpec.Values.Length;
+                markerlen += 1 + 16 + tableConfigs[i].Table.Values.Length;
             }
 
             this.WriteMarkerHeader(JpegConstants.Markers.DHT, markerlen);
-            for (int i = 0; i < tables.Length; i++)
+            for (int i = 0; i < tableConfigs.Length; i++)
             {
-                JpegHuffmanTableConfig table = tables[i];
+                JpegHuffmanTableConfig tableConfig = tableConfigs[i];
 
-                int header = (table.Class << 4) | table.DestinationIndex;
+                int header = (tableConfig.Class << 4) | tableConfig.DestinationIndex;
                 this.outputStream.WriteByte((byte)header);
-                this.outputStream.Write(table.TableSpec.Count);
-                this.outputStream.Write(table.TableSpec.Values);
+                this.outputStream.Write(tableConfig.Table.Count);
+                this.outputStream.Write(tableConfig.Table.Values);
 
-                this.scanEncoder.BuildHuffmanTable(table);
+                this.scanEncoder.BuildHuffmanTable(tableConfig);
             }
         }
 
@@ -749,37 +746,42 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
         /// <param name="metadata">Jpeg metadata instance.</param>
         /// <param name="luminanceQuantTable">Output luminance quantization table.</param>
         /// <param name="chrominanceQuantTable">Output chrominance quantization table.</param>
-        private void InitQuantizationTables(int componentCount, JpegMetadata metadata, out Block8x8F luminanceQuantTable, out Block8x8F chrominanceQuantTable)
+        private void InitQuantizationTables(JpegQuantizationTableConfig[] configs, JpegMetadata metadata)
         {
-            int lumaQuality;
-            int chromaQuality;
-            if (this.quality.HasValue)
-            {
-                lumaQuality = this.quality.Value;
-                chromaQuality = this.quality.Value;
-            }
-            else
-            {
-                lumaQuality = metadata.LuminanceQuality;
-                chromaQuality = metadata.ChrominanceQuality;
-            }
+            int dataLen = configs.Length * (1 + Block8x8F.Size);
 
-            // Luminance
-            lumaQuality = Numerics.Clamp(lumaQuality, 1, 100);
-            luminanceQuantTable = Quantization.ScaleLuminanceTable(lumaQuality);
+            // Marker + quantization table lengths.
+            int markerlen = 2 + dataLen;
+            this.WriteMarkerHeader(JpegConstants.Markers.DQT, markerlen);
+
+            byte[] buffer = new byte[dataLen];
+            int offset = 0;
 
-            // Chrominance
-            chrominanceQuantTable = default;
-            if (componentCount > 1)
+            for (int i = 0; i < configs.Length; i++)
             {
-                chromaQuality = Numerics.Clamp(chromaQuality, 1, 100);
-                chrominanceQuantTable = Quantization.ScaleChrominanceTable(chromaQuality);
+                JpegQuantizationTableConfig config = configs[i];
 
-                if (!this.colorType.HasValue)
+                // write to the output stream
+                buffer[offset++] = (byte)config.DestinationIndex;
+                for (int j = 0; j < Block8x8F.Size; j++)
                 {
-                    this.colorType = chromaQuality >= 91 ? JpegEncodingMode.YCbCrRatio444 : JpegEncodingMode.YCbCrRatio420;
+                    buffer[offset++] = (byte)(uint)config.Table[ZigZag.ZigZagOrder[j]];
                 }
+
+                // apply scaling and save into buffer
+                int quality = GetQualityForTable(config.DestinationIndex, this.quality, metadata);
+                this.QuantizationTables[config.DestinationIndex] = Quantization.ScaleQuantizationTable(quality, config.Table);
             }
+
+            // write filled buffer to the stream
+            this.outputStream.Write(buffer);
+
+            static int GetQualityForTable(int destIndex, int? encoderQuality, JpegMetadata metadata) => destIndex switch
+            {
+                0 => encoderQuality ?? metadata.LuminanceQuality,
+                1 => encoderQuality ?? metadata.ChrominanceQuality,
+                _ => encoderQuality ?? metadata.Quality,
+            };
         }
     }
 }