Add derived format info types and allow persistance of palette lengths

src/ImageSharp/Formats/Bmp/BmpDecoderCore.cs

@@ -10,6 +10,7 @@ using SixLabors.ImageSharp.Memory;
 using SixLabors.ImageSharp.MetaData;
 using SixLabors.ImageSharp.PixelFormats;
 using SixLabors.Memory;
+using SixLabors.Primitives;
 
 namespace SixLabors.ImageSharp.Formats.Bmp
 {
@@ -164,7 +165,9 @@ namespace SixLabors.ImageSharp.Formats.Bmp
         public IImageInfo Identify(Stream stream)
         {
             this.ReadImageHeaders(stream, out _, out _);
-            return new ImageInfo(new PixelTypeInfo(this.infoHeader.BitsPerPixel), this.infoHeader.Width, this.infoHeader.Height, this.metaData);
+
+            var size = new Size(this.infoHeader.Width, this.infoHeader.Height);
+            return new BmpInfo(new PixelTypeInfo(this.infoHeader.BitsPerPixel), size, this.metaData);
         }
 
         /// <summary>
@@ -175,10 +178,7 @@ namespace SixLabors.ImageSharp.Formats.Bmp
         /// <param name="inverted">Whether the bitmap is inverted.</param>
         /// <returns>The <see cref="int"/> representing the inverted value.</returns>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        private static int Invert(int y, int height, bool inverted)
-        {
-            return (!inverted) ? height - y - 1 : y;
-        }
+        private static int Invert(int y, int height, bool inverted) => (!inverted) ? height - y - 1 : y;
 
         /// <summary>
         /// Calculates the amount of bytes to pad a row.
@@ -206,10 +206,7 @@ namespace SixLabors.ImageSharp.Formats.Bmp
         /// <param name="value">The masked and shifted value</param>
         /// <returns>The <see cref="byte"/></returns>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        private static byte GetBytesFrom5BitValue(int value)
-        {
-            return (byte)((value << 3) | (value >> 2));
-        }
+        private static byte GetBytesFrom5BitValue(int value) => (byte)((value << 3) | (value >> 2));
 
         /// <summary>
         /// Looks up color values and builds the image from de-compressed RLE8 data.
@@ -524,8 +521,10 @@ namespace SixLabors.ImageSharp.Formats.Bmp
             }
 
             // Resolution is stored in PPM.
-            var meta = new ImageMetaData();
-            meta.ResolutionUnits = PixelResolutionUnit.PixelsPerMeter;
+            var meta = new ImageMetaData
+            {
+                ResolutionUnits = PixelResolutionUnit.PixelsPerMeter
+            };
             if (this.infoHeader.XPelsPerMeter > 0 && this.infoHeader.YPelsPerMeter > 0)
             {
                 meta.HorizontalResolution = this.infoHeader.XPelsPerMeter;

src/ImageSharp/Formats/Bmp/BmpInfo.cs

@@ -0,0 +1,25 @@
+// Copyright (c) Six Labors and contributors.
+// Licensed under the Apache License, Version 2.0.
+
+using SixLabors.ImageSharp.MetaData;
+using SixLabors.Primitives;
+
+namespace SixLabors.ImageSharp.Formats.Bmp
+{
+    /// <summary>
+    /// Contains information about the bmp including dimensions, pixel type information and additional metadata.
+    /// </summary>
+    public class BmpInfo : ImageInfo
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="BmpInfo" /> class.
+        /// </summary>
+        /// <param name="pixelType">The image pixel type information.</param>
+        /// <param name="size">The size of the image in pixels.</param>
+        /// <param name="metaData">The images metadata.</param>
+        internal BmpInfo(PixelTypeInfo pixelType, Size size, ImageMetaData metaData)
+            : base(pixelType, size, metaData)
+        {
+        }
+    }
+}

src/ImageSharp/Formats/Gif/GifDecoderCore.cs

@@ -55,6 +55,11 @@ namespace SixLabors.ImageSharp.Formats.Gif
         /// </summary>
         private GifGraphicControlExtension graphicsControlExtension;
 
+        /// <summary>
+        /// The image desciptor.
+        /// </summary>
+        private GifImageDescriptor imageDescriptor;
+
         /// <summary>
         /// The metadata
         /// </summary>
@@ -120,8 +125,7 @@ namespace SixLabors.ImageSharp.Formats.Gif
                     }
                     else if (nextFlag == GifConstants.ExtensionIntroducer)
                     {
-                        int label = stream.ReadByte();
-                        switch (label)
+                        switch (stream.ReadByte())
                         {
                             case GifConstants.GraphicControlLabel:
                                 this.ReadGraphicalControlExtension();
@@ -178,13 +182,11 @@ namespace SixLabors.ImageSharp.Formats.Gif
                 {
                     if (nextFlag == GifConstants.ImageLabel)
                     {
-                        // Skip image block
-                        this.Skip(0);
+                        this.ReadImageDescriptor();
                     }
                     else if (nextFlag == GifConstants.ExtensionIntroducer)
                     {
-                        int label = stream.ReadByte();
-                        switch (label)
+                        switch (stream.ReadByte())
                         {
                             case GifConstants.GraphicControlLabel:
 
@@ -224,7 +226,17 @@ namespace SixLabors.ImageSharp.Formats.Gif
                 this.globalColorTable?.Dispose();
             }
 
-            return new ImageInfo(new PixelTypeInfo(this.logicalScreenDescriptor.BitsPerPixel), this.logicalScreenDescriptor.Width, this.logicalScreenDescriptor.Height, this.metaData);
+            GifColorTableMode colorTableMode = this.logicalScreenDescriptor.GlobalColorTableFlag
+            ? GifColorTableMode.Global
+            : GifColorTableMode.Local;
+
+            var size = new Size(this.logicalScreenDescriptor.Width, this.logicalScreenDescriptor.Height);
+
+            return new GifInfo(
+                colorTableMode,
+                new PixelTypeInfo(this.logicalScreenDescriptor.BitsPerPixel),
+                size,
+                this.metaData);
         }
 
         /// <summary>
@@ -238,14 +250,13 @@ namespace SixLabors.ImageSharp.Formats.Gif
         }
 
         /// <summary>
-        /// Reads the image descriptor
+        /// Reads the image descriptor.
         /// </summary>
-        /// <returns><see cref="GifImageDescriptor"/></returns>
-        private GifImageDescriptor ReadImageDescriptor()
+        private void ReadImageDescriptor()
         {
             this.stream.Read(this.buffer, 0, 9);
 
-            return GifImageDescriptor.Parse(this.buffer);
+            this.imageDescriptor = GifImageDescriptor.Parse(this.buffer);
         }
 
         /// <summary>
@@ -312,25 +323,25 @@ namespace SixLabors.ImageSharp.Formats.Gif
         private void ReadFrame<TPixel>(ref Image<TPixel> image, ref ImageFrame<TPixel> previousFrame)
             where TPixel : struct, IPixel<TPixel>
         {
-            GifImageDescriptor imageDescriptor = this.ReadImageDescriptor();
+            this.ReadImageDescriptor();
 
             IManagedByteBuffer localColorTable = null;
             IManagedByteBuffer indices = null;
             try
             {
                 // Determine the color table for this frame. If there is a local one, use it otherwise use the global color table.
-                if (imageDescriptor.LocalColorTableFlag)
+                if (this.imageDescriptor.LocalColorTableFlag)
                 {
-                    int length = imageDescriptor.LocalColorTableSize * 3;
+                    int length = this.imageDescriptor.LocalColorTableSize * 3;
                     localColorTable = this.configuration.MemoryAllocator.AllocateManagedByteBuffer(length, AllocationOptions.Clean);
                     this.stream.Read(localColorTable.Array, 0, length);
                 }
 
-                indices = this.configuration.MemoryAllocator.AllocateManagedByteBuffer(imageDescriptor.Width * imageDescriptor.Height, AllocationOptions.Clean);
+                indices = this.configuration.MemoryAllocator.AllocateManagedByteBuffer(this.imageDescriptor.Width * this.imageDescriptor.Height, AllocationOptions.Clean);
 
-                this.ReadFrameIndices(imageDescriptor, indices.GetSpan());
+                this.ReadFrameIndices(this.imageDescriptor, indices.GetSpan());
                 ReadOnlySpan<Rgb24> colorTable = MemoryMarshal.Cast<byte, Rgb24>((localColorTable ?? this.globalColorTable).GetSpan());
-                this.ReadFrameColors(ref image, ref previousFrame, indices.GetSpan(), colorTable, imageDescriptor);
+                this.ReadFrameColors(ref image, ref previousFrame, indices.GetSpan(), colorTable, this.imageDescriptor);
 
                 // Skip any remaining blocks
                 this.Skip(0);
@@ -508,6 +519,18 @@ namespace SixLabors.ImageSharp.Formats.Gif
                 meta.FrameDelay = this.graphicsControlExtension.DelayTime;
             }
 
+            // Frames can either use the global table or their own local table.
+            if (this.logicalScreenDescriptor.GlobalColorTableFlag
+                && this.logicalScreenDescriptor.GlobalColorTableSize > 0)
+            {
+                meta.ColorTableLength = this.logicalScreenDescriptor.GlobalColorTableSize;
+            }
+            else if (this.imageDescriptor.LocalColorTableFlag
+                && this.imageDescriptor.LocalColorTableSize > 0)
+            {
+                meta.ColorTableLength = this.imageDescriptor.LocalColorTableSize;
+            }
+
             meta.DisposalMethod = this.graphicsControlExtension.DisposalMethod;
         }
 

src/ImageSharp/Formats/Gif/GifEncoderCore.cs

@@ -146,7 +146,8 @@ namespace SixLabors.ImageSharp.Formats.Gif
                 }
                 else
                 {
-                    using (QuantizedFrame<TPixel> paletteQuantized = palleteQuantizer.CreateFrameQuantizer(() => quantized.Palette).QuantizeFrame(frame))
+                    using (QuantizedFrame<TPixel> paletteQuantized
+                        = palleteQuantizer.CreateFrameQuantizer(() => quantized.Palette).QuantizeFrame(frame))
                     {
                         this.WriteImageData(paletteQuantized, stream);
                     }
@@ -157,13 +158,25 @@ namespace SixLabors.ImageSharp.Formats.Gif
         private void EncodeLocal<TPixel>(Image<TPixel> image, QuantizedFrame<TPixel> quantized, Stream stream)
             where TPixel : struct, IPixel<TPixel>
         {
+            ImageFrame<TPixel> previousFrame = null;
             foreach (ImageFrame<TPixel> frame in image.Frames)
             {
                 if (quantized is null)
                 {
-                    quantized = this.quantizer.CreateFrameQuantizer<TPixel>().QuantizeFrame(frame);
+                    // Allow each frame to be encoded at whatever color depth the frame designates if set.
+                    if (previousFrame != null
+                        && previousFrame.MetaData.ColorTableLength != frame.MetaData.ColorTableLength
+                        && frame.MetaData.ColorTableLength > 0)
+                    {
+                        quantized = this.quantizer.CreateFrameQuantizer<TPixel>(frame.MetaData.ColorTableLength).QuantizeFrame(frame);
+                    }
+                    else
+                    {
+                        quantized = this.quantizer.CreateFrameQuantizer<TPixel>().QuantizeFrame(frame);
+                    }
                 }
 
+                this.bitDepth = ImageMaths.GetBitsNeededForColorDepth(quantized.Palette.Length).Clamp(1, 8);
                 this.WriteGraphicalControlExtension(frame.MetaData, this.GetTransparentIndex(quantized), stream);
                 this.WriteImageDescriptor(frame, true, stream);
                 this.WriteColorTable(quantized, stream);
@@ -171,6 +184,7 @@ namespace SixLabors.ImageSharp.Formats.Gif
 
                 quantized?.Dispose();
                 quantized = null; // So next frame can regenerate it
+                previousFrame = frame;
             }
         }
 
@@ -210,10 +224,7 @@ namespace SixLabors.ImageSharp.Formats.Gif
         /// </summary>
         /// <param name="stream">The stream to write to.</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        private void WriteHeader(Stream stream)
-        {
-            stream.Write(GifConstants.MagicNumber, 0, GifConstants.MagicNumber.Length);
-        }
+        private void WriteHeader(Stream stream) => stream.Write(GifConstants.MagicNumber, 0, GifConstants.MagicNumber.Length);
 
         /// <summary>
         /// Writes the logical screen descriptor to the stream.
@@ -226,7 +237,7 @@ namespace SixLabors.ImageSharp.Formats.Gif
         private void WriteLogicalScreenDescriptor<TPixel>(Image<TPixel> image, int transparencyIndex, bool useGlobalTable, Stream stream)
             where TPixel : struct, IPixel<TPixel>
         {
-            byte packedValue = GifLogicalScreenDescriptor.GetPackedValue(useGlobalTable, this.bitDepth - 1, false, this.bitDepth - 1);
+            byte packedValue = GifLogicalScreenDescriptor.GetPackedValue(useGlobalTable, this.bitDepth, false, this.bitDepth - 1);
 
             // The Pixel Aspect Ratio is defined to be the quotient of the pixel's
             // width over its height.  The value range in this field allows
@@ -382,7 +393,7 @@ namespace SixLabors.ImageSharp.Formats.Gif
                 localColorTableFlag: hasColorTable,
                 interfaceFlag: false,
                 sortFlag: false,
-                localColorTableSize: (byte)this.bitDepth);
+                localColorTableSize: this.bitDepth - 1);
 
             var descriptor = new GifImageDescriptor(
                 left: 0,
@@ -407,7 +418,8 @@ namespace SixLabors.ImageSharp.Formats.Gif
         {
             int pixelCount = image.Palette.Length;
 
-            int colorTableLength = (int)Math.Pow(2, this.bitDepth) * 3; // The maximium number of colors for the bit depth
+            // The maximium number of colors for the bit depth
+            int colorTableLength = (int)Math.Pow(2, this.bitDepth) * 3;
             Rgb24 rgb = default;
 
             using (IManagedByteBuffer colorTable = this.memoryAllocator.AllocateManagedByteBuffer(colorTableLength))

src/ImageSharp/Formats/Gif/GifInfo.cs

@@ -0,0 +1,33 @@
+// Copyright (c) Six Labors and contributors.
+// Licensed under the Apache License, Version 2.0.
+
+using SixLabors.ImageSharp.MetaData;
+using SixLabors.Primitives;
+
+namespace SixLabors.ImageSharp.Formats.Gif
+{
+    /// <summary>
+    /// Contains information about the bmp including dimensions, pixel type information and additional metadata.
+    /// </summary>
+    public class GifInfo : ImageInfo
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="GifInfo" /> class.
+        /// </summary>
+        /// <param name="colorTableMode">The color table mode.</param>
+        /// <param name="pixelType">The image pixel type information.</param>
+        /// <param name="size">The size of the image in pixels.</param>
+        /// <param name="metaData">The images metadata.</param>
+        internal GifInfo(
+            GifColorTableMode colorTableMode,
+            PixelTypeInfo pixelType,
+            Size size,
+            ImageMetaData metaData)
+            : base(pixelType, size, metaData) => this.ColorTableMode = colorTableMode;
+
+        /// <summary>
+        /// Gets the color table mode.
+        /// </summary>
+        public GifColorTableMode ColorTableMode { get; }
+    }
+}

src/ImageSharp/Formats/Gif/Sections/GifImageDescriptor.cs

@@ -81,7 +81,7 @@ namespace SixLabors.ImageSharp.Formats.Gif
             return MemoryMarshal.Cast<byte, GifImageDescriptor>(buffer)[0];
         }
 
-        public static byte GetPackedValue(bool localColorTableFlag, bool interfaceFlag, bool sortFlag, byte localColorTableSize)
+        public static byte GetPackedValue(bool localColorTableFlag, bool interfaceFlag, bool sortFlag, int localColorTableSize)
         {
             /*
             Local Color Table Flag     | 1 Bit

src/ImageSharp/Formats/Jpeg/JpegDecoderCore.cs

@@ -234,7 +234,8 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
             this.InitExifProfile();
             this.InitIccProfile();
             this.InitDerivedMetaDataProperties();
-            return new ImageInfo(new PixelTypeInfo(this.BitsPerPixel), this.ImageWidth, this.ImageHeight, this.MetaData);
+
+            return new JpegInfo(new PixelTypeInfo(this.BitsPerPixel), new Size(this.ImageWidth, this.ImageHeight), this.MetaData);
         }
 
         /// <summary>
@@ -899,9 +900,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
         /// <param name="values">The values</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         private void BuildHuffmanTable(HuffmanTables tables, int index, ReadOnlySpan<byte> codeLengths, ReadOnlySpan<byte> values)
-        {
-            tables[index] = new HuffmanTable(this.configuration.MemoryAllocator, codeLengths, values);
-        }
+            => tables[index] = new HuffmanTable(this.configuration.MemoryAllocator, codeLengths, values);
 
         /// <summary>
         /// Reads a <see cref="ushort"/> from the stream advancing it by two bytes

src/ImageSharp/Formats/Jpeg/JpegInfo.cs

@@ -0,0 +1,25 @@
+// Copyright (c) Six Labors and contributors.
+// Licensed under the Apache License, Version 2.0.
+
+using SixLabors.ImageSharp.MetaData;
+using SixLabors.Primitives;
+
+namespace SixLabors.ImageSharp.Formats.Jpeg
+{
+    /// <summary>
+    /// Contains information about the bmp including dimensions, pixel type information and additional metadata.
+    /// </summary>
+    public class JpegInfo : ImageInfo
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="JpegInfo" /> class.
+        /// </summary>
+        /// <param name="pixelType">The image pixel type information.</param>
+        /// <param name="size">The size of the image in pixels.</param>
+        /// <param name="metaData">The images metadata.</param>
+        internal JpegInfo(PixelTypeInfo pixelType, Size size, ImageMetaData metaData)
+            : base(pixelType, size, metaData)
+        {
+        }
+    }
+}

src/ImageSharp/Formats/Png/PngDecoderCore.cs

@@ -10,7 +10,6 @@ using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 using System.Text;
 using SixLabors.ImageSharp.Advanced;
-using SixLabors.ImageSharp.Common.Helpers;
 using SixLabors.ImageSharp.Formats.Png.Filters;
 using SixLabors.ImageSharp.Formats.Png.Zlib;
 using SixLabors.ImageSharp.Memory;
@@ -18,6 +17,7 @@ using SixLabors.ImageSharp.MetaData;
 using SixLabors.ImageSharp.MetaData.Profiles.Exif;
 using SixLabors.ImageSharp.PixelFormats;
 using SixLabors.Memory;
+using SixLabors.Primitives;
 
 namespace SixLabors.ImageSharp.Formats.Png
 {
@@ -349,7 +349,7 @@ namespace SixLabors.ImageSharp.Formats.Png
                 throw new ImageFormatException("PNG Image does not contain a header chunk");
             }
 
-            return new ImageInfo(new PixelTypeInfo(this.CalculateBitsPerPixel()), this.header.Width, this.header.Height, metadata);
+            return new PngInfo(new PixelTypeInfo(this.CalculateBitsPerPixel()), new Size(this.header.Width, this.header.Height), metadata);
         }
 
         /// <summary>
@@ -360,9 +360,7 @@ namespace SixLabors.ImageSharp.Formats.Png
         /// <returns>The <see cref="int"/></returns>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         private static byte ReadByteLittleEndian(ReadOnlySpan<byte> buffer, int offset)
-        {
-            return (byte)(((buffer[offset] & 0xFF) << 16) | (buffer[offset + 1] & 0xFF));
-        }
+            => (byte)(((buffer[offset] & 0xFF) << 16) | (buffer[offset + 1] & 0xFF));
 
         /// <summary>
         /// Attempts to convert a byte array to a new array where each value in the original array is represented by the

src/ImageSharp/Formats/Png/PngInfo.cs

@@ -0,0 +1,25 @@
+// Copyright (c) Six Labors and contributors.
+// Licensed under the Apache License, Version 2.0.
+
+using SixLabors.ImageSharp.MetaData;
+using SixLabors.Primitives;
+
+namespace SixLabors.ImageSharp.Formats.Png
+{
+    /// <summary>
+    /// Contains information about the bmp including dimensions, pixel type information and additional metadata.
+    /// </summary>
+    public class PngInfo : ImageInfo
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="PngInfo" /> class.
+        /// </summary>
+        /// <param name="pixelType">The image pixel type information.</param>
+        /// <param name="size">The size of the image in pixels.</param>
+        /// <param name="metaData">The images metadata.</param>
+        internal PngInfo(PixelTypeInfo pixelType, Size size, ImageMetaData metaData)
+            : base(pixelType, size, metaData)
+        {
+        }
+    }
+}

src/ImageSharp/ImageInfo.cs

@@ -3,26 +3,26 @@
 
 using SixLabors.ImageSharp.Formats;
 using SixLabors.ImageSharp.MetaData;
+using SixLabors.Primitives;
 
 namespace SixLabors.ImageSharp
 {
     /// <summary>
     /// Contains information about the image including dimensions, pixel type information and additional metadata
     /// </summary>
-    internal sealed class ImageInfo : IImageInfo
+    public abstract class ImageInfo : IImageInfo
     {
         /// <summary>
         /// Initializes a new instance of the <see cref="ImageInfo"/> class.
         /// </summary>
         /// <param name="pixelType">The image pixel type information.</param>
-        /// <param name="width">The width of the image in pixels.</param>
-        /// <param name="height">The height of the image in pixels.</param>
+        /// <param name="size">The size of the image in pixels.</param>
         /// <param name="metaData">The images metadata.</param>
-        public ImageInfo(PixelTypeInfo pixelType, int width, int height, ImageMetaData metaData)
+        protected ImageInfo(PixelTypeInfo pixelType, Size size, ImageMetaData metaData)
         {
             this.PixelType = pixelType;
-            this.Width = width;
-            this.Height = height;
+            this.Width = size.Width;
+            this.Height = size.Height;
             this.MetaData = metaData;
         }
 

src/ImageSharp/MetaData/ImageFrameMetaData.cs

@@ -28,10 +28,18 @@ namespace SixLabors.ImageSharp.MetaData
         {
             DebugGuard.NotNull(other, nameof(other));
 
+            this.ColorTableLength = other.ColorTableLength;
             this.FrameDelay = other.FrameDelay;
             this.DisposalMethod = other.DisposalMethod;
         }
 
+        /// <summary>
+        /// Gets or sets the length of the color table for paletted images.
+        /// If not 0, then this field indicates the maximum number of colors to use when quantizing the
+        /// image frame.
+        /// </summary>
+        public int ColorTableLength { get; set; }
+
         /// <summary>
         /// Gets or sets the frame delay for animated images.
         /// If not 0, when utilized in Gif animation, this field specifies the number of hundredths (1/100) of a second to
@@ -51,9 +59,6 @@ namespace SixLabors.ImageSharp.MetaData
         /// Clones this ImageFrameMetaData.
         /// </summary>
         /// <returns>The cloned instance.</returns>
-        public ImageFrameMetaData Clone()
-        {
-            return new ImageFrameMetaData(this);
-        }
+        public ImageFrameMetaData Clone() => new ImageFrameMetaData(this);
     }
 }

src/ImageSharp/Processing/Processors/Quantization/IQuantizer.cs

@@ -23,5 +23,14 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
         /// <returns>The <see cref="IFrameQuantizer{TPixel}"/></returns>
         IFrameQuantizer<TPixel> CreateFrameQuantizer<TPixel>()
             where TPixel : struct, IPixel<TPixel>;
+
+        /// <summary>
+        /// Creates the generic frame quantizer
+        /// </summary>
+        /// <typeparam name="TPixel">The pixel format.</typeparam>
+        /// <param name="maxColors">The maximum number of colors to hold in the color palette.</param>
+        /// <returns>The <see cref="IFrameQuantizer{TPixel}"/></returns>
+        IFrameQuantizer<TPixel> CreateFrameQuantizer<TPixel>(int maxColors)
+            where TPixel : struct, IPixel<TPixel>;
     }
 }

src/ImageSharp/Processing/Processors/Quantization/OctreeFrameQuantizer{TPixel}.cs

@@ -22,7 +22,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
         /// <summary>
         /// Maximum allowed color depth
         /// </summary>
-        private readonly byte colors;
+        private readonly int colors;
 
         /// <summary>
         /// Stores the tree
@@ -43,9 +43,23 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
         /// the second pass quantizes a color based on the nodes in the tree
         /// </remarks>
         public OctreeFrameQuantizer(OctreeQuantizer quantizer)
+            : this(quantizer, quantizer.MaxColors)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="OctreeFrameQuantizer{TPixel}"/> class.
+        /// </summary>
+        /// <param name="quantizer">The octree quantizer.</param>
+        /// <param name="maxColors">The maximum number of colors to hold in the color palette.</param>
+        /// <remarks>
+        /// The Octree quantizer is a two pass algorithm. The initial pass sets up the Octree,
+        /// the second pass quantizes a color based on the nodes in the tree
+        /// </remarks>
+        public OctreeFrameQuantizer(OctreeQuantizer quantizer, int maxColors)
             : base(quantizer, false)
         {
-            this.colors = (byte)quantizer.MaxColors;
+            this.colors = maxColors;
             this.octree = new Octree(ImageMaths.GetBitsNeededForColorDepth(this.colors).Clamp(1, 8));
         }
 
@@ -261,13 +275,13 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
             [MethodImpl(MethodImplOptions.AggressiveInlining)]
             public TPixel[] Palletize(int colorCount)
             {
-                while (this.Leaves > colorCount)
+                while (this.Leaves > colorCount - 1)
                 {
                     this.Reduce();
                 }
 
                 // Now palletize the nodes
-                var palette = new TPixel[colorCount + 1];
+                var palette = new TPixel[colorCount];
 
                 int paletteIndex = 0;
                 this.root.ConstructPalette(palette, ref paletteIndex);
@@ -285,10 +299,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
             /// The <see cref="int"/>.
             /// </returns>
             [MethodImpl(MethodImplOptions.AggressiveInlining)]
-            public int GetPaletteIndex(ref TPixel pixel, ref Rgba32 rgba)
-            {
-                return this.root.GetPaletteIndex(ref pixel, 0, ref rgba);
-            }
+            public int GetPaletteIndex(ref TPixel pixel, ref Rgba32 rgba) => this.root.GetPaletteIndex(ref pixel, 0, ref rgba);
 
             /// <summary>
             /// Keep track of the previous node that was quantized
@@ -297,10 +308,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
             /// The node last quantized
             /// </param>
             [MethodImpl(MethodImplOptions.AggressiveInlining)]
-            protected void TrackPrevious(OctreeNode node)
-            {
-                this.previousNode = node;
-            }
+            protected void TrackPrevious(OctreeNode node) => this.previousNode = node;
 
             /// <summary>
             /// Reduce the depth of the tree

src/ImageSharp/Processing/Processors/Quantization/OctreeQuantizer.cs

@@ -15,6 +15,11 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
     /// </summary>
     public class OctreeQuantizer : IQuantizer
     {
+        /// <summary>
+        /// The default maximum number of colors to use when quantizing the image.
+        /// </summary>
+        public const int DefaultMaxColors = 256;
+
         /// <summary>
         /// Initializes a new instance of the <see cref="OctreeQuantizer"/> class.
         /// </summary>
@@ -26,7 +31,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
         /// <summary>
         /// Initializes a new instance of the <see cref="OctreeQuantizer"/> class.
         /// </summary>
-        /// <param name="maxColors">The maximum number of colors to hold in the color palette</param>
+        /// <param name="maxColors">The maximum number of colors to hold in the color palette.</param>
         public OctreeQuantizer(int maxColors)
             : this(GetDiffuser(true), maxColors)
         {
@@ -37,7 +42,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
         /// </summary>
         /// <param name="dither">Whether to apply dithering to the output image</param>
         public OctreeQuantizer(bool dither)
-            : this(GetDiffuser(dither), 255)
+            : this(GetDiffuser(dither), DefaultMaxColors)
         {
         }
 
@@ -46,7 +51,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
         /// </summary>
         /// <param name="diffuser">The error diffusion algorithm, if any, to apply to the output image</param>
         public OctreeQuantizer(IErrorDiffuser diffuser)
-            : this(diffuser, 255)
+            : this(diffuser, DefaultMaxColors)
         {
         }
 
@@ -57,10 +62,8 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
         /// <param name="maxColors">The maximum number of colors to hold in the color palette</param>
         public OctreeQuantizer(IErrorDiffuser diffuser, int maxColors)
         {
-            Guard.MustBeBetweenOrEqualTo(maxColors, 1, 255, nameof(maxColors));
-
             this.Diffuser = diffuser;
-            this.MaxColors = maxColors;
+            this.MaxColors = maxColors.Clamp(1, DefaultMaxColors);
         }
 
         /// <inheritdoc />
@@ -76,6 +79,14 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
             where TPixel : struct, IPixel<TPixel>
             => new OctreeFrameQuantizer<TPixel>(this);
 
+        /// <inheritdoc/>
+        public IFrameQuantizer<TPixel> CreateFrameQuantizer<TPixel>(int maxColors)
+            where TPixel : struct, IPixel<TPixel>
+        {
+            maxColors = maxColors.Clamp(1, DefaultMaxColors);
+            return new OctreeFrameQuantizer<TPixel>(this, maxColors);
+        }
+
         private static IErrorDiffuser GetDiffuser(bool dither) => dither ? KnownDiffusers.FloydSteinberg : null;
     }
 }

src/ImageSharp/Processing/Processors/Quantization/PaletteFrameQuantizer{TPixel}.cs

@@ -36,6 +36,8 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
         public PaletteFrameQuantizer(PaletteQuantizer quantizer, TPixel[] colors)
             : base(quantizer, true)
         {
+            // TODO: Why is this value constrained? Gif has limitations but theoretically
+            // we might want to reduce the palette of an image to greater than that limitation.
             Guard.MustBeBetweenOrEqualTo(colors.Length, 1, 256, nameof(colors));
             this.palette = colors;
             this.paletteVector = new Vector4[this.palette.Length];

src/ImageSharp/Processing/Processors/Quantization/PaletteQuantizer.cs

@@ -37,10 +37,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
         /// Initializes a new instance of the <see cref="PaletteQuantizer"/> class.
         /// </summary>
         /// <param name="diffuser">The error diffusion algorithm, if any, to apply to the output image</param>
-        public PaletteQuantizer(IErrorDiffuser diffuser)
-        {
-            this.Diffuser = diffuser;
-        }
+        public PaletteQuantizer(IErrorDiffuser diffuser) => this.Diffuser = diffuser;
 
         /// <inheritdoc />
         public IErrorDiffuser Diffuser { get; }
@@ -50,6 +47,21 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
             where TPixel : struct, IPixel<TPixel>
             => this.CreateFrameQuantizer(() => NamedColors<TPixel>.WebSafePalette);
 
+        /// <inheritdoc/>
+        public IFrameQuantizer<TPixel> CreateFrameQuantizer<TPixel>(int maxColors)
+            where TPixel : struct, IPixel<TPixel>
+        {
+            TPixel[] websafe = NamedColors<TPixel>.WebSafePalette;
+            int max = Math.Min(maxColors, websafe.Length);
+
+            if (max != websafe.Length)
+            {
+                return this.CreateFrameQuantizer(() => NamedColors<TPixel>.WebSafePalette.AsSpan(0, max).ToArray());
+            }
+
+            return this.CreateFrameQuantizer(() => websafe);
+        }
+
         /// <summary>
         /// Gets the palette to use to quantize the image.
         /// </summary>

src/ImageSharp/Processing/Processors/Quantization/WuFrameQuantizer{TPixel}.cs

@@ -3,7 +3,6 @@
 
 using System;
 using System.Buffers;
-using System.Collections.Generic;
 using System.Numerics;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
@@ -128,11 +127,22 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
         /// the second pass quantizes a color based on the position in the histogram.
         /// </remarks>
         public WuFrameQuantizer(WuQuantizer quantizer)
-            : base(quantizer, false)
+            : this(quantizer, quantizer.MaxColors)
         {
-            this.colors = quantizer.MaxColors;
         }
 
+        /// <summary>
+        /// Initializes a new instance of the <see cref="WuFrameQuantizer{TPixel}"/> class.
+        /// </summary>
+        /// <param name="quantizer">The wu quantizer.</param>
+        /// <param name="maxColors">The maximum number of colors to hold in the color palette.</param>
+        /// <remarks>
+        /// The Wu quantizer is a two pass algorithm. The initial pass sets up the 3-D color histogram,
+        /// the second pass quantizes a color based on the position in the histogram.
+        /// </remarks>
+        public WuFrameQuantizer(WuQuantizer quantizer, int maxColors)
+            : base(quantizer, false) => this.colors = maxColors;
+
         /// <inheritdoc/>
         public override QuantizedFrame<TPixel> QuantizeFrame(ImageFrame<TPixel> image)
         {

src/ImageSharp/Processing/Processors/Quantization/WuQuantizer.cs

@@ -14,6 +14,11 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
     /// </summary>
     public class WuQuantizer : IQuantizer
     {
+        /// <summary>
+        /// The default maximum number of colors to use when quantizing the image.
+        /// </summary>
+        public const int DefaultMaxColors = 256;
+
         /// <summary>
         /// Initializes a new instance of the <see cref="WuQuantizer"/> class.
         /// </summary>
@@ -36,7 +41,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
         /// </summary>
         /// <param name="dither">Whether to apply dithering to the output image</param>
         public WuQuantizer(bool dither)
-            : this(GetDiffuser(dither), 255)
+            : this(GetDiffuser(dither), DefaultMaxColors)
         {
         }
 
@@ -45,7 +50,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
         /// </summary>
         /// <param name="diffuser">The error diffusion algorithm, if any, to apply to the output image</param>
         public WuQuantizer(IErrorDiffuser diffuser)
-            : this(diffuser, 255)
+            : this(diffuser, DefaultMaxColors)
         {
         }
 
@@ -56,10 +61,8 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
         /// <param name="maxColors">The maximum number of colors to hold in the color palette</param>
         public WuQuantizer(IErrorDiffuser diffuser, int maxColors)
         {
-            Guard.MustBeBetweenOrEqualTo(maxColors, 1, 255, nameof(maxColors));
-
             this.Diffuser = diffuser;
-            this.MaxColors = maxColors;
+            this.MaxColors = maxColors.Clamp(1, DefaultMaxColors);
         }
 
         /// <inheritdoc />
@@ -75,6 +78,14 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
             where TPixel : struct, IPixel<TPixel>
             => new WuFrameQuantizer<TPixel>(this);
 
+        /// <inheritdoc/>
+        public IFrameQuantizer<TPixel> CreateFrameQuantizer<TPixel>(int maxColors)
+            where TPixel : struct, IPixel<TPixel>
+        {
+            maxColors = maxColors.Clamp(1, DefaultMaxColors);
+            return new WuFrameQuantizer<TPixel>(this, maxColors);
+        }
+
         private static IErrorDiffuser GetDiffuser(bool dither) => dither ? KnownDiffusers.FloydSteinberg : null;
     }
 }

tests/ImageSharp.Tests/Formats/Gif/GifEncoderTests.cs

@@ -179,5 +179,44 @@ namespace SixLabors.ImageSharp.Tests.Formats.Gif
                 Assert.True(fileInfoGlobal.Length < fileInfoLocal.Length);
             }
         }
+
+        [Fact]
+        public void NonMutatingEncodePreservesPaletteCount()
+        {
+            using (var inStream = new MemoryStream(TestFile.Create(TestImages.Gif.Leo).Bytes))
+            using (var outStream = new MemoryStream())
+            {
+                var info = (GifInfo)Image.Identify(inStream);
+                GifColorTableMode colorMode = info.ColorTableMode;
+                inStream.Position = 0;
+
+                var image = Image.Load(inStream);
+                var encoder = new GifEncoder()
+                {
+                    ColorTableMode = colorMode,
+                    Quantizer = new OctreeQuantizer(image.Frames.RootFrame.MetaData.ColorTableLength)
+                };
+
+                image.Save(outStream, encoder);
+                outStream.Position = 0;
+
+                var cloneInfo = (GifInfo)Image.Identify(outStream);
+                outStream.Position = 0;
+                var clone = Image.Load(outStream);
+
+                // Gifiddle and Cyotek GifInfo say this image has 64 colors.
+                Assert.Equal(64, image.Frames.RootFrame.MetaData.ColorTableLength);
+                Assert.Equal(info.ColorTableMode, cloneInfo.ColorTableMode);
+
+                for (int i = 0; i < image.Frames.Count; i++)
+                {
+                    Assert.Equal(image.Frames[i].MetaData.ColorTableLength, clone.Frames[i].MetaData.ColorTableLength);
+                    Assert.Equal(image.Frames[i].MetaData.FrameDelay, clone.Frames[i].MetaData.FrameDelay);
+                }
+
+                image.Dispose();
+                clone.Dispose();
+            }
+        }
     }
 }

tests/ImageSharp.Tests/ImageInfoTests.cs

@@ -2,6 +2,10 @@
 // Licensed under the Apache License, Version 2.0.
 
 using SixLabors.ImageSharp.Formats;
+using SixLabors.ImageSharp.Formats.Bmp;
+using SixLabors.ImageSharp.Formats.Gif;
+using SixLabors.ImageSharp.Formats.Jpeg;
+using SixLabors.ImageSharp.Formats.Png;
 using SixLabors.ImageSharp.MetaData;
 using SixLabors.Primitives;
 
@@ -12,7 +16,7 @@ namespace SixLabors.ImageSharp.Tests
     public class ImageInfoTests
     {
         [Fact]
-        public void ImageInfoInitializesCorrectly()
+        public void JpegInfoInitializesCorrectly()
         {
             const int Width = 50;
             const int Height = 60;
@@ -21,7 +25,7 @@ namespace SixLabors.ImageSharp.Tests
             var pixelType = new PixelTypeInfo(8);
             var meta = new ImageMetaData();
 
-            var info = new ImageInfo(pixelType, Width, Height, meta);
+            var info = new JpegInfo(pixelType, size, meta);
 
             Assert.Equal(pixelType, info.PixelType);
             Assert.Equal(Width, info.Width);
@@ -30,5 +34,67 @@ namespace SixLabors.ImageSharp.Tests
             Assert.Equal(rectangle, info.Bounds());
             Assert.Equal(meta, info.MetaData);
         }
+
+        [Fact]
+        public void BmpInfoInitializesCorrectly()
+        {
+            const int Width = 50;
+            const int Height = 60;
+            var size = new Size(Width, Height);
+            var rectangle = new Rectangle(0, 0, Width, Height);
+            var pixelType = new PixelTypeInfo(8);
+            var meta = new ImageMetaData();
+
+            var info = new BmpInfo(pixelType, size, meta);
+
+            Assert.Equal(pixelType, info.PixelType);
+            Assert.Equal(Width, info.Width);
+            Assert.Equal(Height, info.Height);
+            Assert.Equal(size, info.Size());
+            Assert.Equal(rectangle, info.Bounds());
+            Assert.Equal(meta, info.MetaData);
+        }
+
+        [Fact]
+        public void PngInfoInitializesCorrectly()
+        {
+            const int Width = 50;
+            const int Height = 60;
+            var size = new Size(Width, Height);
+            var rectangle = new Rectangle(0, 0, Width, Height);
+            var pixelType = new PixelTypeInfo(8);
+            var meta = new ImageMetaData();
+
+            var info = new PngInfo(pixelType, size, meta);
+
+            Assert.Equal(pixelType, info.PixelType);
+            Assert.Equal(Width, info.Width);
+            Assert.Equal(Height, info.Height);
+            Assert.Equal(size, info.Size());
+            Assert.Equal(rectangle, info.Bounds());
+            Assert.Equal(meta, info.MetaData);
+        }
+
+        [Fact]
+        public void GifInfoInitializesCorrectly()
+        {
+            const GifColorTableMode mode = GifColorTableMode.Local;
+            const int Width = 50;
+            const int Height = 60;
+            var size = new Size(Width, Height);
+            var rectangle = new Rectangle(0, 0, Width, Height);
+            var pixelType = new PixelTypeInfo(8);
+            var meta = new ImageMetaData();
+
+            var info = new GifInfo(mode, pixelType, size, meta);
+
+            Assert.Equal(mode, info.ColorTableMode);
+            Assert.Equal(pixelType, info.PixelType);
+            Assert.Equal(Width, info.Width);
+            Assert.Equal(Height, info.Height);
+            Assert.Equal(size, info.Size());
+            Assert.Equal(rectangle, info.Bounds());
+            Assert.Equal(meta, info.MetaData);
+        }
     }
 }

tests/ImageSharp.Tests/MetaData/ImageFrameMetaDataTests.cs

@@ -1,7 +1,6 @@
 // Copyright (c) Six Labors and contributors.
 // Licensed under the Apache License, Version 2.0.
 
-using SixLabors.ImageSharp.Formats;
 using SixLabors.ImageSharp.Formats.Gif;
 using SixLabors.ImageSharp.MetaData;
 using Xunit;
@@ -16,14 +15,22 @@ namespace SixLabors.ImageSharp.Tests
         [Fact]
         public void ConstructorImageFrameMetaData()
         {
-            ImageFrameMetaData metaData = new ImageFrameMetaData();
-            metaData.FrameDelay = 42;
-            metaData.DisposalMethod = DisposalMethod.RestoreToBackground;
+            const int frameDelay = 42;
+            const int colorTableLength = 128;
+            const DisposalMethod disposalMethod = DisposalMethod.RestoreToBackground;
 
-            ImageFrameMetaData clone = new ImageFrameMetaData(metaData);
+            var metaData = new ImageFrameMetaData
+            {
+                FrameDelay = frameDelay,
+                ColorTableLength = colorTableLength,
+                DisposalMethod = disposalMethod
+            };
 
-            Assert.Equal(42, clone.FrameDelay);
-            Assert.Equal(DisposalMethod.RestoreToBackground, clone.DisposalMethod);
+            var clone = new ImageFrameMetaData(metaData);
+
+            Assert.Equal(frameDelay, clone.FrameDelay);
+            Assert.Equal(colorTableLength, clone.ColorTableLength);
+            Assert.Equal(disposalMethod, clone.DisposalMethod);
         }
     }
 }

tests/ImageSharp.Tests/TestImages.cs

@@ -201,6 +201,7 @@ namespace SixLabors.ImageSharp.Tests
             public const string Cheers = "Gif/cheers.gif";
             public const string Trans = "Gif/trans.gif";
             public const string Kumin = "Gif/kumin.gif";
+            public const string Leo = "Gif/leo.gif";
             public const string Ratio4x1 = "Gif/base_4x1.gif";
             public const string Ratio1x4 = "Gif/base_1x4.gif";
 
@@ -211,7 +212,7 @@ namespace SixLabors.ImageSharp.Tests
                 public const string BadDescriptorWidth = "Gif/issues/issue403_baddescriptorwidth.gif";
             }
 
-            public static readonly string[] All = { Rings, Giphy, Cheers, Trans, Kumin, Ratio4x1, Ratio1x4 };
+            public static readonly string[] All = { Rings, Giphy, Cheers, Trans, Kumin, Leo, Ratio4x1, Ratio1x4 };
         }
     }
 }

tests/ImageSharp.Tests/TestUtilities/ImageProviders/FileProvider.cs

@@ -55,9 +55,20 @@ namespace SixLabors.ImageSharp.Tests
 
                 public bool Equals(Key other)
                 {
-                    if (other is null) return false;
-                    if (ReferenceEquals(this, other)) return true;
-                    if (!this.commonValues.Equals(other.commonValues)) return false;
+                    if (other is null)
+                    {
+                        return false;
+                    }
+
+                    if (ReferenceEquals(this, other))
+                    {
+                        return true;
+                    }
+
+                    if (!this.commonValues.Equals(other.commonValues))
+                    {
+                        return false;
+                    }
 
                     if (this.decoderParameters.Count != other.decoderParameters.Count)
                     {
@@ -66,8 +77,7 @@ namespace SixLabors.ImageSharp.Tests
 
                     foreach (KeyValuePair<string, object> kv in this.decoderParameters)
                     {
-                        object otherVal;
-                        if (!other.decoderParameters.TryGetValue(kv.Key, out otherVal))
+                        if (!other.decoderParameters.TryGetValue(kv.Key, out object otherVal))
                         {
                             return false;
                         }
@@ -81,26 +91,29 @@ namespace SixLabors.ImageSharp.Tests
 
                 public override bool Equals(object obj)
                 {
-                    if (obj is null) return false;
-                    if (ReferenceEquals(this, obj)) return true;
-                    if (obj.GetType() != this.GetType()) return false;
+                    if (obj is null)
+                    {
+                        return false;
+                    }
+
+                    if (ReferenceEquals(this, obj))
+                    {
+                        return true;
+                    }
+
+                    if (obj.GetType() != this.GetType())
+                    {
+                        return false;
+                    }
+
                     return this.Equals((Key)obj);
                 }
 
-                public override int GetHashCode()
-                {
-                    return this.commonValues.GetHashCode();
-                }
+                public override int GetHashCode() => this.commonValues.GetHashCode();
 
-                public static bool operator ==(Key left, Key right)
-                {
-                    return Equals(left, right);
-                }
+                public static bool operator ==(Key left, Key right) => Equals(left, right);
 
-                public static bool operator !=(Key left, Key right)
-                {
-                    return !Equals(left, right);
-                }
+                public static bool operator !=(Key left, Key right) => !Equals(left, right);
             }
 
             private static readonly ConcurrentDictionary<Key, Image<TPixel>> cache = new ConcurrentDictionary<Key, Image<TPixel>>();
@@ -111,10 +124,7 @@ namespace SixLabors.ImageSharp.Tests
             {
             }
 
-            public FileProvider(string filePath)
-            {
-                this.FilePath = filePath;
-            }
+            public FileProvider(string filePath) => this.FilePath = filePath;
 
             /// <summary>
             /// Gets the file path relative to the "~/tests/images" folder
@@ -135,12 +145,12 @@ namespace SixLabors.ImageSharp.Tests
 
                 if (!TestEnvironment.Is64BitProcess)
                 {
-                    return LoadImage(decoder);
+                    return this.LoadImage(decoder);
                 }
 
                 var key = new Key(this.PixelType, this.FilePath, decoder);
 
-                Image<TPixel> cachedImage = cache.GetOrAdd(key, fn => { return LoadImage(decoder); });
+                Image<TPixel> cachedImage = cache.GetOrAdd(key, _ => this.LoadImage(decoder));
 
                 return cachedImage.Clone();
             }

tests/ImageSharp.Tests/TestUtilities/ReferenceCodecs/SystemDrawingReferenceDecoder.cs

@@ -48,7 +48,16 @@ namespace SixLabors.ImageSharp.Tests.TestUtilities.ReferenceCodecs
             using (var sourceBitmap = new System.Drawing.Bitmap(stream))
             {
                 var pixelType = new PixelTypeInfo(System.Drawing.Image.GetPixelFormatSize(sourceBitmap.PixelFormat));
-                return new ImageInfo(pixelType, sourceBitmap.Width, sourceBitmap.Height, new ImageMetaData());
+                var size = new SixLabors.Primitives.Size(sourceBitmap.Width, sourceBitmap.Height);
+                return new SystemDrawingInfo(pixelType, size, new ImageMetaData());
+            }
+        }
+
+        private class SystemDrawingInfo : ImageInfo
+        {
+            public SystemDrawingInfo(PixelTypeInfo pixelType, SixLabors.Primitives.Size size, ImageMetaData metaData)
+                : base(pixelType, size, metaData)
+            {
             }
         }
     }

tests/Images/Input/Gif/leo.gif

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:6ee2bf4404165d534dcbfaebece0eee2a93999c47aec26850a7021b8c5d25f5c
+size 454544