Optimization, new jpeg metadata fields

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

@@ -247,7 +247,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
 
             this.scanBuffer = new JpegBitReader(this.stream);
 
-            bool fullScan = this.frame.Progressive || this.frame.MultiScan;
+            bool fullScan = this.frame.Progressive || !this.frame.Interleaved;
             this.frame.AllocateComponents(fullScan);
 
             if (this.frame.Progressive)

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

@@ -121,7 +121,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
 
             this.scanBuffer = new JpegBitReader(this.stream);
 
-            bool fullScan = this.frame.Progressive || this.frame.MultiScan;
+            bool fullScan = this.frame.Progressive || !this.frame.Interleaved;
             this.frame.AllocateComponents(fullScan);
 
             if (!this.frame.Progressive)

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

@@ -12,7 +12,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
     {
         public JpegFrame(JpegFileMarker sofMarker, byte precision, int width, int height, byte componentCount)
         {
-            this.Extended = sofMarker.Marker is JpegConstants.Markers.SOF1 or JpegConstants.Markers.SOF9;
+            this.IsExtended = 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;
@@ -27,7 +27,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
         /// <summary>
         /// Gets a value indicating whether the frame uses the extended specification.
         /// </summary>
-        public bool Extended { get; private set; }
+        public bool IsExtended { get; private set; }
 
         /// <summary>
         /// Gets a value indicating whether the frame uses the progressive specification.
@@ -40,7 +40,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
         /// <remarks>
         /// This is true for progressive and baseline non-interleaved images.
         /// </remarks>
-        public bool MultiScan { get; set; }
+        public bool Interleaved { get; set; }
 
         /// <summary>
         /// Gets the precision.

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

@@ -135,7 +135,65 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Encoder
             tables[tableConfig.DestinationIndex] = new HuffmanLut(tableConfig.Table);
         }
 
-        public void EncodeScanBaselineInterleaved<TPixel>(JpegFrame frame, SpectralConverter<TPixel> converter, CancellationToken cancellationToken)
+        public void EncodeScanBaselineInterleaved<TPixel>(JpegEncodingColor color, JpegFrame frame, SpectralConverter<TPixel> converter, CancellationToken cancellationToken)
+            where TPixel : unmanaged, IPixel<TPixel>
+        {
+            switch (color)
+            {
+                case JpegEncodingColor.YCbCrRatio444:
+                case JpegEncodingColor.Rgb:
+                    this.EncodeScanBaselineInterleaved444(frame, converter, cancellationToken);
+                    break;
+                case JpegEncodingColor.YCbCrRatio420:
+                    this.EncodeScanBaselineInterleaved420(frame, converter, cancellationToken);
+                    break;
+                default:
+                    this.EncodeScanBaselineInterleavedArbitrarySampling(frame, converter, cancellationToken);
+                    break;
+            }
+
+            this.FlushRemainingBytes();
+        }
+
+        public void EncodeScanBaselineSingleComponent<TPixel>(JpegFrame frame, SpectralConverter<TPixel> converter, CancellationToken cancellationToken)
+            where TPixel : unmanaged, IPixel<TPixel>
+        {
+            JpegComponent component = frame.Components[0];
+
+            int mcuLines = frame.McusPerColumn;
+            int w = component.WidthInBlocks;
+
+            ref HuffmanLut dcHuffmanTable = ref this.dcHuffmanTables[component.DcTableId];
+            ref HuffmanLut acHuffmanTable = ref this.acHuffmanTables[component.AcTableId];
+
+            for (int i = 0; i < mcuLines; i++)
+            {
+                cancellationToken.ThrowIfCancellationRequested();
+
+                // Convert from pixels to spectral via given converter
+                converter.ConvertStrideBaseline();
+
+                // Encode spectral to binary
+                Span<Block8x8> blockSpan = component.SpectralBlocks.DangerousGetRowSpan(y: 0);
+                ref Block8x8 blockRef = ref MemoryMarshal.GetReference(blockSpan);
+
+                for (int k = 0; k < w; k++)
+                {
+                    this.WriteBlock(
+                        component,
+                        ref Unsafe.Add(ref blockRef, k),
+                        ref dcHuffmanTable,
+                        ref acHuffmanTable);
+
+                    if (this.IsStreamFlushNeeded)
+                    {
+                        this.FlushToStream();
+                    }
+                }
+            }
+        }
+
+        private void EncodeScanBaselineInterleavedArbitrarySampling<TPixel>(JpegFrame frame, SpectralConverter<TPixel> converter, CancellationToken cancellationToken)
             where TPixel : unmanaged, IPixel<TPixel>
         {
             int mcu = 0;
@@ -154,7 +212,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Encoder
                 {
                     // Scan an interleaved mcu... process components in order
                     int mcuCol = mcu % mcusPerLine;
-                    for (int k = 0; k < frame.ComponentCount; k++)
+                    for (int k = 0; k < frame.Components.Length; k++)
                     {
                         JpegComponent component = frame.Components[k];
 
@@ -192,24 +250,30 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Encoder
                     }
                 }
             }
-
-            this.FlushRemainingBytes();
         }
 
-        public void EncodeScanBaselineSingleComponent<TPixel>(JpegFrame frame, SpectralConverter<TPixel> converter, CancellationToken cancellationToken)
+        private void EncodeScanBaselineInterleaved444<TPixel>(JpegFrame frame, SpectralConverter<TPixel> converter, CancellationToken cancellationToken)
             where TPixel : unmanaged, IPixel<TPixel>
         {
-            // DEBUG INITIALIZATION SETUP
-            frame.AllocateComponents(fullScan: false);
+            int mcusPerColumn = frame.McusPerColumn;
+            int mcusPerLine = frame.McusPerLine;
 
-            JpegComponent component = frame.Components[0];
-            int mcuLines = frame.McusPerColumn;
-            int w = component.WidthInBlocks;
-            int h = component.SamplingFactors.Height;
-            ref HuffmanLut dcHuffmanTable = ref this.dcHuffmanTables[component.DcTableId];
-            ref HuffmanLut acHuffmanTable = ref this.acHuffmanTables[component.AcTableId];
+            JpegComponent c2 = frame.Components[2];
+            JpegComponent c1 = frame.Components[1];
+            JpegComponent c0 = frame.Components[0];
 
-            for (int i = 0; i < mcuLines; i++)
+            ref HuffmanLut c0dcHuffmanTable = ref this.dcHuffmanTables[c0.DcTableId];
+            ref HuffmanLut c0acHuffmanTable = ref this.acHuffmanTables[c0.AcTableId];
+            ref HuffmanLut c1dcHuffmanTable = ref this.dcHuffmanTables[c1.DcTableId];
+            ref HuffmanLut c1acHuffmanTable = ref this.acHuffmanTables[c1.AcTableId];
+            ref HuffmanLut c2dcHuffmanTable = ref this.dcHuffmanTables[c2.DcTableId];
+            ref HuffmanLut c2acHuffmanTable = ref this.acHuffmanTables[c2.AcTableId];
+
+            ref Block8x8 c0BlockRef = ref MemoryMarshal.GetReference(c0.SpectralBlocks.DangerousGetRowSpan(y: 0));
+            ref Block8x8 c1BlockRef = ref MemoryMarshal.GetReference(c1.SpectralBlocks.DangerousGetRowSpan(y: 0));
+            ref Block8x8 c2BlockRef = ref MemoryMarshal.GetReference(c2.SpectralBlocks.DangerousGetRowSpan(y: 0));
+
+            for (int j = 0; j < mcusPerColumn; j++)
             {
                 cancellationToken.ThrowIfCancellationRequested();
 
@@ -217,28 +281,40 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Encoder
                 converter.ConvertStrideBaseline();
 
                 // Encode spectral to binary
-                for (int j = 0; j < h; j++)
+                for (int i = 0; i < mcusPerLine; i++)
                 {
-                    Span<Block8x8> blockSpan = component.SpectralBlocks.DangerousGetRowSpan(j);
-                    ref Block8x8 blockRef = ref MemoryMarshal.GetReference(blockSpan);
+                    this.WriteBlock(
+                        c0,
+                        ref Unsafe.Add(ref c0BlockRef, i),
+                        ref c0dcHuffmanTable,
+                        ref c0acHuffmanTable);
+
+                    this.WriteBlock(
+                        c1,
+                        ref Unsafe.Add(ref c1BlockRef, i),
+                        ref c1dcHuffmanTable,
+                        ref c1acHuffmanTable);
+
+                    this.WriteBlock(
+                        c2,
+                        ref Unsafe.Add(ref c2BlockRef, i),
+                        ref c2dcHuffmanTable,
+                        ref c2acHuffmanTable);
 
-                    for (int k = 0; k < w; k++)
+                    if (this.IsStreamFlushNeeded)
                     {
-                        this.WriteBlock(
-                            component,
-                            ref Unsafe.Add(ref blockRef, k),
-                            ref dcHuffmanTable,
-                            ref acHuffmanTable);
-
-                        if (this.IsStreamFlushNeeded)
-                        {
-                            this.FlushToStream();
-                        }
+                        this.FlushToStream();
                     }
                 }
             }
         }
 
+        private void EncodeScanBaselineInterleaved420<TPixel>(JpegFrame frame, SpectralConverter<TPixel> converter, CancellationToken cancellationToken)
+            where TPixel : unmanaged, IPixel<TPixel>
+        {
+            throw new NotImplementedException();
+        }
+
         private void WriteBlock(
             JpegComponent component,
             ref Block8x8 block,

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

@@ -37,7 +37,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Encoder
             this.McusPerLine = (int)Numerics.DivideCeil((uint)image.Width, (uint)maxSubFactorH * 8);
             this.McusPerColumn = (int)Numerics.DivideCeil((uint)image.Height, (uint)maxSubFactorV * 8);
 
-            for (int i = 0; i < this.ComponentCount; i++)
+            for (int i = 0; i < this.Components.Length; i++)
             {
                 JpegComponent component = this.Components[i];
                 component.Init(this, maxSubFactorH, maxSubFactorV);
@@ -50,8 +50,6 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Encoder
 
         public int PixelWidth { get; private set; }
 
-        public int ComponentCount => this.Components.Length;
-
         public JpegComponent[] Components { get; }
 
         public int McusPerLine { get; }
@@ -70,7 +68,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Encoder
 
         public void AllocateComponents(bool fullScan)
         {
-            for (int i = 0; i < this.ComponentCount; i++)
+            for (int i = 0; i < this.Components.Length; i++)
             {
                 JpegComponent component = this.Components[i];
                 component.AllocateSpectral(fullScan);

src/ImageSharp/Formats/Jpeg/IJpegEncoderOptions.cs

@@ -14,5 +14,14 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
         /// Defaults to <value>75</value>.
         /// </summary>
         public int? Quality { get; set; }
+
+        /// <summary>
+        /// Gets or sets the component encoding mode.
+        /// </summary>
+        /// <remarks>
+        /// Interleaved encoding mode encodes all color components in a single scan.
+        /// Non-interleaved encoding mode encodes each color component in a separate scan.
+        /// </remarks>
+        public bool? Interleaved { get; set; }
     }
 }

src/ImageSharp/Formats/Jpeg/JpegDecoderCore.cs

@@ -488,6 +488,8 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
                 // Read on.
                 fileMarker = FindNextFileMarker(this.markerBuffer, stream);
             }
+
+            this.Metadata.GetJpegMetadata().Interleaved = this.Frame.Interleaved;
         }
 
         /// <inheritdoc/>
@@ -1178,6 +1180,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
             }
 
             this.Frame = new JpegFrame(frameMarker, precision, frameWidth, frameHeight, componentCount);
+            this.Metadata.GetJpegMetadata().Progressive = this.Frame.Progressive;
 
             remaining -= length;
 
@@ -1386,7 +1389,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
             // selectorsCount*2 bytes: component index + huffman tables indices
             stream.Read(this.temp, 0, selectorsBytes);
 
-            this.Frame.MultiScan = this.Frame.ComponentCount != selectorsCount;
+            this.Frame.Interleaved = this.Frame.ComponentCount == selectorsCount;
             for (int i = 0; i < selectorsBytes; i += 2)
             {
                 // 1 byte: Component id

src/ImageSharp/Formats/Jpeg/JpegEncoder.cs

@@ -24,6 +24,9 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
         /// <inheritdoc/>
         public int? Quality { get; set; }
 
+        /// <inheritdoc/>
+        public bool? Interleaved { get; set; }
+
         /// <summary>
         /// Sets jpeg color for encoding.
         /// </summary>

src/ImageSharp/Formats/Jpeg/JpegEncoderCore.cs

@@ -38,9 +38,8 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
         /// </summary>
         private readonly int? quality;
 
-        /// <summary>
-        /// Gets or sets the colorspace to use.
-        /// </summary>
+        private readonly bool? interleaved;
+
         private JpegEncodingColor? colorType;
 
         private JpegFrameConfig frameConfig;
@@ -60,6 +59,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
         public JpegEncoderCore(IJpegEncoderOptions options, JpegFrameConfig frameConfig)
         {
             this.quality = options.Quality;
+            this.interleaved = options.Interleaved;
 
             this.frameConfig = frameConfig;
             this.colorType = frameConfig.EncodingColor;
@@ -121,20 +121,25 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
             // Write the quantization tables.
             this.WriteDefineQuantizationTables(this.frameConfig.QuantizationTables, jpegMetadata);
 
-            // Write the scan header.
-            this.WriteStartOfScan(this.frameConfig.Components.Length, this.frameConfig.Components);
-
             var spectralConverter = new SpectralConverter<TPixel>(frame, image, this.QuantizationTables, Configuration.Default);
 
-            // TODO: change this for non-interleaved scans
-            frame.AllocateComponents(fullScan: false);
-            if (frame.ComponentCount > 1)
+            if (frame.Components.Length == 1)
+            {
+                frame.AllocateComponents(fullScan: false);
+
+                this.WriteStartOfScan(this.frameConfig.Components);
+                this.scanEncoder.EncodeScanBaselineSingleComponent(frame, spectralConverter, cancellationToken);
+            }
+            else if (this.interleaved ?? jpegMetadata.Interleaved ?? true)
             {
-                this.scanEncoder.EncodeScanBaselineInterleaved(frame, spectralConverter, cancellationToken);
+                frame.AllocateComponents(fullScan: false);
+
+                this.WriteStartOfScan(this.frameConfig.Components);
+                this.scanEncoder.EncodeScanBaselineInterleaved(this.frameConfig.EncodingColor, frame, spectralConverter, cancellationToken);
             }
             else
             {
-                this.scanEncoder.EncodeScanBaselineSingleComponent(frame, spectralConverter, cancellationToken);
+                throw new NotImplementedException();
             }
 
             // Write the End Of Image marker.
@@ -143,50 +148,6 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
             stream.Flush();
         }
 
-        /// <summary>
-        /// If color type was not set, set it based on the given image.
-        /// Note, if there is no metadata and the image has multiple components this method
-        /// returns <see langword="null"/> defering the field assignment
-        /// to <see cref="WriteDefineQuantizationTables"/>.
-        /// </summary>
-        private static JpegEncodingColor? GetFallbackColorType<TPixel>(Image<TPixel> image)
-            where TPixel : unmanaged, IPixel<TPixel>
-        {
-            // First inspect the image metadata.
-            JpegEncodingColor? colorType = null;
-            JpegMetadata metadata = image.Metadata.GetJpegMetadata();
-            if (IsSupportedColorType(metadata.ColorType))
-            {
-                return metadata.ColorType;
-            }
-
-            // Secondly, inspect the pixel type.
-            // TODO: PixelTypeInfo should contain a component count!
-            bool isGrayscale =
-                typeof(TPixel) == typeof(L8) || typeof(TPixel) == typeof(L16) ||
-                typeof(TPixel) == typeof(La16) || typeof(TPixel) == typeof(La32);
-
-            // We don't set multi-component color types here since we can set it based upon
-            // the quality in InitQuantizationTables.
-            if (isGrayscale)
-            {
-                colorType = JpegEncodingColor.Luminance;
-            }
-
-            return colorType;
-        }
-
-        /// <summary>
-        /// Returns true, if the color type is supported by the encoder.
-        /// </summary>
-        /// <param name="colorType">The color type.</param>
-        /// <returns>true, if color type is supported.</returns>
-        private static bool IsSupportedColorType(JpegEncodingColor? colorType)
-            => colorType == JpegEncodingColor.YCbCrRatio444
-            || colorType == JpegEncodingColor.YCbCrRatio420
-            || colorType == JpegEncodingColor.Luminance
-            || colorType == JpegEncodingColor.Rgb;
-
         /// <summary>
         /// Write the start of image marker.
         /// </summary>
@@ -611,7 +572,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
         /// <summary>
         /// Writes the StartOfScan marker.
         /// </summary>
-        private void WriteStartOfScan(int componentCount, JpegComponentConfig[] components)
+        private void WriteStartOfScan(Span<JpegComponentConfig> components)
         {
             // Write the SOS (Start Of Scan) marker "\xff\xda" followed by 12 bytes:
             // - the marker length "\x00\x0c",
@@ -626,13 +587,13 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
             this.buffer[1] = JpegConstants.Markers.SOS;
 
             // Length (high byte, low byte), must be 6 + 2 * (number of components in scan)
-            int sosSize = 6 + (2 * componentCount);
+            int sosSize = 6 + (2 * components.Length);
             this.buffer[2] = 0x00;
             this.buffer[3] = (byte)sosSize;
-            this.buffer[4] = (byte)componentCount; // Number of components in a scan
+            this.buffer[4] = (byte)components.Length; // Number of components in a scan
 
             // Components data
-            for (int i = 0; i < componentCount; i++)
+            for (int i = 0; i < components.Length; i++)
             {
                 int i2 = 2 * i;
 

src/ImageSharp/Formats/Jpeg/JpegMetadata.cs

@@ -99,9 +99,26 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
         }
 
         /// <summary>
-        /// Gets or sets the color type.
+        /// Gets the color type.
         /// </summary>
-        public JpegEncodingColor? ColorType { get; set; }
+        public JpegEncodingColor? ColorType { get; internal set; }
+
+        /// <summary>
+        /// Gets the component encoding mode.
+        /// </summary>
+        /// <remarks>
+        /// Interleaved encoding mode encodes all color components in a single scan.
+        /// Non-interleaved encoding mode encodes each color component in a separate scan.
+        /// </remarks>
+        public bool? Interleaved { get; internal set; }
+
+        /// <summary>
+        /// Gets the scan encoding mode.
+        /// </summary>
+        /// <remarks>
+        /// Progressive jpeg images encode component data across multiple scans.
+        /// </remarks>
+        public bool? Progressive { get; internal set; }
 
         /// <inheritdoc/>
         public IDeepCloneable DeepClone() => new JpegMetadata(this);

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

@@ -151,7 +151,7 @@ namespace SixLabors.ImageSharp.Tests.Formats.Jpg
                 {
                     // Due to underlying architecture, baseline interleaved jpegs would inject spectral data during parsing
                     // Progressive and multi-scan images must be loaded manually
-                    if (this.frame.Progressive || this.frame.MultiScan)
+                    if (this.frame.Progressive || !this.frame.Interleaved)
                     {
                         LibJpegTools.ComponentData[] components = this.spectralData.Components;
                         for (int i = 0; i < components.Length; i++)