Moar gif updates

Former-commit-id: e3548b3f5fb82d262a1054c6d2ff89c24f86206d
Former-commit-id: d9ba2a7a4c74231ba7b8f7c90a87567c41b0605a
Former-commit-id: a6b6bac2b10088c73838b5177636b5c9db6424c4

src/ImageProcessor/Formats/Gif/GifConstants.cs

@@ -0,0 +1,68 @@
+// --------------------------------------------------------------------------------------------------------------------
+// <copyright file="GifConstants.cs" company="James South">
+//   Copyright © James South and contributors.
+//   Licensed under the Apache License, Version 2.0.
+// </copyright>
+// <summary>
+//   Constants that define specific points within a gif.
+// </summary>
+// --------------------------------------------------------------------------------------------------------------------
+
+namespace ImageProcessor.Formats
+{
+    /// <summary>
+    /// Constants that define specific points within a gif.
+    /// </summary>
+    internal sealed class GifConstants
+    {
+        /// <summary>
+        /// The maximum comment length.
+        /// </summary>
+        public const int MaxCommentLength = 1024 * 8;
+
+        /// <summary>
+        /// The extension block introducer <value>!</value>.
+        /// </summary>
+        public const byte ExtensionIntroducer = 0x21;
+
+        /// <summary>
+        /// The terminator.
+        /// </summary>
+        public const byte Terminator = 0;
+
+        /// <summary>
+        /// The image label introducer <value>,</value>.
+        /// </summary>
+        public const byte ImageLabel = 0x2C;
+
+        /// <summary>
+        /// The end introducer trailer <value>;</value>.
+        /// </summary>
+        public const byte EndIntroducer = 0x3B;
+
+        /// <summary>
+        /// The application extension label.
+        /// </summary>
+        public const byte ApplicationExtensionLabel = 0xFF;
+
+        /// <summary>
+        /// The comment label.
+        /// </summary>
+        public const byte CommentLabel = 0xFE;
+
+        /// <summary>
+        /// The image descriptor label <value>,</value>.
+        /// </summary>
+        public const byte ImageDescriptorLabel = 0x2C;
+
+        /// <summary>
+        /// The plain text label.
+        /// </summary>
+        public const byte PlainTextLabel = 0x01;
+
+        /// <summary>
+        /// The graphic control label.
+        /// </summary>
+        public const byte GraphicControlLabel = 0xF9;
+    }
+}

src/ImageProcessor/Formats/Gif/GifDecoder.cs

@@ -24,6 +24,9 @@ namespace ImageProcessor.Formats
         /// <value>The size of the header.</value>
         public int HeaderSize => 6;
 
+        internal GifDecoderCore CoreDecoder { get; private set; }
+
+
         /// <summary>
         /// Returns a value indicating whether the <see cref="IImageDecoder"/> supports the specified
         /// file header.
@@ -34,7 +37,7 @@ namespace ImageProcessor.Formats
         /// </returns>
         public bool IsSupportedFileExtension(string extension)
         {
-            Guard.NotNullOrEmpty(extension, "extension");
+            Guard.NotNullOrEmpty(extension, nameof(extension));
 
             extension = extension.StartsWith(".") ? extension.Substring(1) : extension;
             return extension.Equals("GIF", StringComparison.OrdinalIgnoreCase);
@@ -66,7 +69,8 @@ namespace ImageProcessor.Formats
         /// <param name="stream">The <see cref="Stream"/> containing image data.</param>
         public void Decode(Image image, Stream stream)
         {
-            new GifDecoderCore().Decode(image, stream);
+            this.CoreDecoder = new GifDecoderCore();
+            this.CoreDecoder.Decode(image, stream);
         }
     }
 }

src/ImageProcessor/Formats/Gif/GifDecoderCore.cs

@@ -24,8 +24,9 @@
         private Stream currentStream;
         private byte[] globalColorTable;
         private byte[] currentFrame;
-        private GifLogicalScreenDescriptor logicalScreenDescriptor;
-        private GifGraphicsControlExtension graphicsControlExtension;
+
+        internal GifLogicalScreenDescriptor LogicalScreenDescriptor { get; set; }
+        internal GifGraphicsControlExtension GraphicsControlExtension { get; set; }
 
         public void Decode(Image image, Stream stream)
         {
@@ -37,16 +38,16 @@
             this.currentStream.Seek(6, SeekOrigin.Current);
             this.ReadLogicalScreenDescriptor();
 
-            if (this.logicalScreenDescriptor.GlobalColorTableFlag)
+            if (this.LogicalScreenDescriptor.GlobalColorTableFlag)
             {
-                this.globalColorTable = new byte[this.logicalScreenDescriptor.GlobalColorTableSize * 3];
+                this.globalColorTable = new byte[this.LogicalScreenDescriptor.GlobalColorTableSize * 3];
 
                 // Read the global color table from the stream
                 stream.Read(this.globalColorTable, 0, this.globalColorTable.Length);
             }
 
             int nextFlag = stream.ReadByte();
-            while (nextFlag != 0)
+            while (nextFlag != Terminator)
             {
                 if (nextFlag == ImageLabel)
                 {
@@ -89,7 +90,7 @@
 
             byte packed = buffer[1];
 
-            this.graphicsControlExtension = new GifGraphicsControlExtension
+            this.GraphicsControlExtension = new GifGraphicsControlExtension
             {
                 DelayTime = BitConverter.ToInt16(buffer, 2),
                 TransparencyIndex = buffer[4],
@@ -134,7 +135,7 @@
 
             byte packed = buffer[4];
 
-            this.logicalScreenDescriptor = new GifLogicalScreenDescriptor
+            this.LogicalScreenDescriptor = new GifLogicalScreenDescriptor
             {
                 Width = BitConverter.ToInt16(buffer, 0),
                 Height = BitConverter.ToInt16(buffer, 2),
@@ -144,16 +145,16 @@
                 GlobalColorTableSize = 2 << (packed & 0x07)
             };
 
-            if (this.logicalScreenDescriptor.GlobalColorTableSize > 255 * 4)
+            if (this.LogicalScreenDescriptor.GlobalColorTableSize > 255 * 4)
             {
                 throw new ImageFormatException(
-                    $"Invalid gif colormap size '{this.logicalScreenDescriptor.GlobalColorTableSize}'");
+                    $"Invalid gif colormap size '{this.LogicalScreenDescriptor.GlobalColorTableSize}'");
             }
 
-            if (this.logicalScreenDescriptor.Width > ImageBase.MaxWidth || this.logicalScreenDescriptor.Height > ImageBase.MaxHeight)
+            if (this.LogicalScreenDescriptor.Width > ImageBase.MaxWidth || this.LogicalScreenDescriptor.Height > ImageBase.MaxHeight)
             {
                 throw new ArgumentOutOfRangeException(
-                    $"The input gif '{this.logicalScreenDescriptor.Width}x{this.logicalScreenDescriptor.Height}' is bigger then the max allowed size '{ImageBase.MaxWidth}x{ImageBase.MaxHeight}'");
+                    $"The input gif '{this.LogicalScreenDescriptor.Width}x{this.LogicalScreenDescriptor.Height}' is bigger then the max allowed size '{ImageBase.MaxWidth}x{ImageBase.MaxHeight}'");
             }
         }
 
@@ -232,8 +233,8 @@
 
         private void ReadFrameColors(byte[] indices, byte[] colorTable, GifImageDescriptor descriptor)
         {
-            int imageWidth = this.logicalScreenDescriptor.Width;
-            int imageHeight = this.logicalScreenDescriptor.Height;
+            int imageWidth = this.LogicalScreenDescriptor.Width;
+            int imageHeight = this.LogicalScreenDescriptor.Height;
 
             if (this.currentFrame == null)
             {
@@ -242,8 +243,8 @@
 
             byte[] lastFrame = null;
 
-            if (this.graphicsControlExtension != null &&
-                this.graphicsControlExtension.DisposalMethod == DisposalMethod.RestoreToPrevious)
+            if (this.GraphicsControlExtension != null &&
+                this.GraphicsControlExtension.DisposalMethod == DisposalMethod.RestoreToPrevious)
             {
                 lastFrame = new byte[imageWidth * imageHeight * 4];
 
@@ -299,9 +300,9 @@
 
                     index = indices[i];
 
-                    if (this.graphicsControlExtension == null ||
-                        this.graphicsControlExtension.TransparencyFlag == false ||
-                        this.graphicsControlExtension.TransparencyIndex != index)
+                    if (this.GraphicsControlExtension == null ||
+                        this.GraphicsControlExtension.TransparencyFlag == false ||
+                        this.GraphicsControlExtension.TransparencyIndex != index)
                     {
                         this.currentFrame[offset * 4 + 0] = colorTable[index * 3 + 2];
                         this.currentFrame[offset * 4 + 1] = colorTable[index * 3 + 1];
@@ -324,9 +325,9 @@
                 currentImage = this.image;
                 currentImage.SetPixels(imageWidth, imageHeight, pixels);
 
-                if (this.graphicsControlExtension != null && this.graphicsControlExtension.DelayTime > 0)
+                if (this.GraphicsControlExtension != null && this.GraphicsControlExtension.DelayTime > 0)
                 {
-                    this.image.FrameDelay = this.graphicsControlExtension.DelayTime;
+                    this.image.FrameDelay = this.GraphicsControlExtension.DelayTime;
                 }
             }
             else
@@ -339,9 +340,9 @@
                 this.image.Frames.Add(frame);
             }
 
-            if (this.graphicsControlExtension != null)
+            if (this.GraphicsControlExtension != null)
             {
-                if (this.graphicsControlExtension.DisposalMethod == DisposalMethod.RestoreToBackground)
+                if (this.GraphicsControlExtension.DisposalMethod == DisposalMethod.RestoreToBackground)
                 {
                     for (int y = descriptor.Top; y < descriptor.Top + descriptor.Height; y++)
                     {
@@ -356,7 +357,7 @@
                         }
                     }
                 }
-                else if (this.graphicsControlExtension.DisposalMethod == DisposalMethod.RestoreToPrevious)
+                else if (this.GraphicsControlExtension.DisposalMethod == DisposalMethod.RestoreToPrevious)
                 {
                     this.currentFrame = lastFrame;
                 }

src/ImageProcessor/Formats/Gif/GifEncoder.cs

@@ -11,7 +11,7 @@ namespace ImageProcessor.Formats
         /// </summary>
         private int quality = 256;
 
-        private ImageBase image;
+        private Image image;
 
         /// <summary>
         /// Gets or sets the quality of output for images.
@@ -58,48 +58,65 @@ namespace ImageProcessor.Formats
         /// <param name="stream">The <see cref="Stream"/> to encode the image data to.</param>
         public void Encode(ImageBase image, Stream stream)
         {
-            Guard.NotNull(image, "image");
-            Guard.NotNull(stream, "stream");
+            Guard.NotNull(image, nameof(image));
+            Guard.NotNull(stream, nameof(stream));
 
-            this.image = image;
+            this.image = (Image)image;
 
             // Write the header.
             // File Header signature and version.
             this.WriteString(stream, "GIF");
             this.WriteString(stream, "89a");
 
-            GifLogicalScreenDescriptor descriptor = new GifLogicalScreenDescriptor
-            {
-                Width = (short)image.Width,
-                Height = (short)image.Height,
-                GlobalColorTableFlag = true,
-                GlobalColorTableSize = this.Quality
-            };
-
-            this.WriteGlobalLogicalScreenDescriptor(stream, descriptor);
-
+            int bitdepth = this.GetBitsNeededForColorDepth(this.Quality) - 1;
 
+            this.WriteGlobalLogicalScreenDescriptor(stream, bitdepth);
+           
+            foreach (ImageFrame frame in this.image.Frames)
+            {
+                this.WriteColorTable(stream, bitdepth);
+                this.WriteGraphicalControlExtension(stream);
+            }
 
             throw new System.NotImplementedException();
         }
 
-        private void WriteGlobalLogicalScreenDescriptor(Stream stream, GifLogicalScreenDescriptor descriptor)
+        private void WriteGlobalLogicalScreenDescriptor(Stream stream, int bitDepth)
         {
+            IImageDecoder decoder = ((Image)this.image).Decoder;
+            GifLogicalScreenDescriptor descriptor;
+
+            // Try and grab an existing descriptor.
+            if (decoder.GetType() == typeof(GifDecoder))
+            {
+                // Ensure the dimensions etc are up to date.
+                descriptor = ((GifDecoder)decoder).CoreDecoder.LogicalScreenDescriptor;
+                descriptor.Width = (short)this.image.Width;
+                descriptor.Height = (short)this.image.Height;
+                descriptor.GlobalColorTableSize = this.Quality;
+            }
+            else
+            {
+                descriptor = new GifLogicalScreenDescriptor
+                {
+                    Width = (short)this.image.Width,
+                    Height = (short)this.image.Height,
+                    GlobalColorTableFlag = true,
+                    GlobalColorTableSize = this.Quality
+                };
+            }
+
             this.WriteShort(stream, descriptor.Width);
             this.WriteShort(stream, descriptor.Width);
-            int size = descriptor.GlobalColorTableSize;
-            int bitdepth = this.GetBitsNeededForColorDepth(size) - 1;
+
             int packed = 0x80 | // 1   : Global color table flag = 1 (GCT used)
                          0x70 | // 2-4 : color resolution
                          0x00 | // 5   : GCT sort flag = 0
-                         bitdepth; // 6-8 : GCT size assume 1:1
+                         bitDepth; // 6-8 : GCT size assume 1:1
 
             this.WriteByte(stream, packed);
             this.WriteByte(stream, descriptor.BackgroundColorIndex); // Background Color Index
             this.WriteByte(stream, descriptor.PixelAspectRatio); // Pixel aspect ratio
-
-            // Write the global color table.
-            this.WriteColorTable(stream, bitdepth);
         }
 
         private void WriteColorTable(Stream stream, int bitDepth)
@@ -127,6 +144,54 @@ namespace ImageProcessor.Formats
             stream.Write(colorTable, 0, colorTableLength);
         }
 
+        private void WriteGraphicalControlExtension(Stream stream)
+        {
+            Image i = ((Image)this.image);
+            IImageDecoder decoder = i.Decoder;
+            GifGraphicsControlExtension extension;
+
+            // Try and grab an existing descriptor.
+            // TODO: Check whether we need to.
+            if (decoder.GetType() == typeof(GifDecoder))
+            {
+                // Ensure the dimensions etc are up to date.
+                extension = ((GifDecoder)decoder).CoreDecoder.GraphicsControlExtension;
+                extension.TransparencyFlag = this.Quality > 1;
+                extension.TransparencyIndex = this.Quality - 1;
+                extension.DelayTime = i.FrameDelay;
+            }
+            else
+            {
+                bool hasTransparent = this.Quality > 1;
+                DisposalMethod disposalMethod = hasTransparent
+                    ? DisposalMethod.RestoreToBackground
+                    : DisposalMethod.Unspecified;
+
+                extension = new GifGraphicsControlExtension()
+                {
+                    DisposalMethod = disposalMethod,
+                    TransparencyFlag = hasTransparent,
+                    TransparencyIndex = this.Quality - 1, // Quantizer set last as transparent.
+                    DelayTime = i.FrameDelay
+                };
+            }
+
+            this.WriteByte(stream, GifConstants.ExtensionIntroducer);
+            this.WriteByte(stream, GifConstants.GraphicControlLabel);
+            this.WriteByte(stream, 4); // Size
+
+            int packed = 0 | // 1-3 : Reserved
+                         (int)extension.DisposalMethod | // 4-6 : Disposal
+                         0 | // 7 : User input - 0 = none
+                         extension.TransparencyIndex;
+
+            this.WriteByte(stream, packed);
+            this.WriteShort(stream, extension.DelayTime);
+            this.WriteByte(stream, GifConstants.Terminator);
+        }
+
+
+
         private void WriteApplicationExtension(Stream stream)
         {
             // TODO: Implement
@@ -146,7 +211,7 @@ namespace ImageProcessor.Formats
         }
 
         /// <summary>
-        /// Writes a short to the given stream.
+        /// Writes a byte to the given stream.
         /// </summary>
         /// <param name="stream">The <see cref="Stream"/> containing image data.</param>
         /// <param name="value">The value to write.</param>

src/ImageProcessor/Formats/Gif/GifGraphicsControlExtension.cs

@@ -42,7 +42,6 @@ namespace ImageProcessor.Formats
         /// If not 0, this field specifies the number of hundredths (1/100) of a second to 
         /// wait before continuing with the processing of the Data Stream. 
         /// The clock starts ticking immediately after the graphic is rendered. 
-        /// This field may be used in conjunction with the User Input Flag field. 
         /// </summary>
         public int DelayTime { get; set; }
     }

src/ImageProcessor/Formats/Gif/LzwEncoder.cs

@@ -63,7 +63,7 @@
 
         // General DEFINEs
 
-        private const int BITS = 12;
+        private const int Bits = 12;
 
         private const int HSIZE = 5003; // 80% occupancy
 
@@ -79,12 +79,12 @@
         //              Joe Orost              (decvax!vax135!petsd!joe)
 
         private int numberOfBits; // number of bits/code
-        private int maxbits = BITS; // user settable max # bits/code
+        private int maxbits = Bits; // user settable max # bits/code
         private int maxcode; // maximum code, given n_bits
-        private int maxmaxcode = 1 << BITS; // should NEVER generate this code
+        private int maxmaxcode = 1 << Bits; // should NEVER generate this code
 
-        private int[] htab = new int[HSIZE];
-        private int[] codetab = new int[HSIZE];
+        private readonly int[] hashTable = new int[HSIZE];
+        private readonly int[] codeTable = new int[HSIZE];
 
         private int hsize = HSIZE; // for dynamic table sizing
 
@@ -168,7 +168,7 @@
         {
             for (int i = 0; i < hsize; ++i)
             {
-                this.htab[i] = -1;
+                this.hashTable[i] = -1;
             }
         }
 
@@ -210,21 +210,21 @@
 
             this.Output(this.ClearCode, outs);
 
-        // TODO: Refactor this. Goto is baaaaaaad!
-        outer_loop:
+            // TODO: Refactor this. Goto is baaaaaaad!
+            //  outer_loop:
             while ((c = this.NextPixel()) != EOF)
             {
                 fcode = (c << this.maxbits) + ent;
                 int i = c << hshift ^ ent;
 
-                if (this.htab[i] == fcode)
+                if (this.hashTable[i] == fcode)
                 {
-                    ent = this.codetab[i];
+                    ent = this.codeTable[i];
                     continue;
                 }
 
                 // non-empty slot
-                if (this.htab[i] >= 0)
+                if (this.hashTable[i] >= 0)
                 {
                     disp = hsize_reg - i; // secondary hash (after G. Knott)
                     if (i == 0)
@@ -239,13 +239,14 @@
                             i += hsize_reg;
                         }
 
-                        if (this.htab[i] == fcode)
+                        if (this.hashTable[i] == fcode)
                         {
-                            ent = this.codetab[i];
-                            goto outer_loop;
+                            ent = this.codeTable[i];
+                            // goto outer_loop;
+                            break;
                         }
                     }
-                    while (this.htab[i] >= 0);
+                    while (this.hashTable[i] >= 0);
                 }
 
                 this.Output(ent, outs);
@@ -253,8 +254,8 @@
 
                 if (this.freeEntry < this.maxmaxcode)
                 {
-                    this.codetab[i] = this.freeEntry++; // code -> hashtable
-                    this.htab[i] = fcode;
+                    this.codeTable[i] = this.freeEntry++; // code -> hashtable
+                    this.hashTable[i] = fcode;
                 }
                 else
                 {

src/ImageProcessor/Image.cs

@@ -98,7 +98,7 @@ namespace ImageProcessor
         public Image(Image other)
             : base(other)
         {
-            Guard.NotNull(other, "other", "Other image cannot be null.");
+            Guard.NotNull(other, nameof(other), "Other image cannot be null.");
 
             foreach (ImageFrame frame in other.Frames)
             {
@@ -120,7 +120,7 @@ namespace ImageProcessor
         /// </param>
         public Image(Stream stream)
         {
-            Guard.NotNull(stream, "stream");
+            Guard.NotNull(stream, nameof(stream));
             this.Load(stream, Decoders);
         }
 
@@ -154,9 +154,8 @@ namespace ImageProcessor
         /// If not 0, this field specifies the number of hundredths (1/100) of a second to 
         /// wait before continuing with the processing of the Data Stream. 
         /// The clock starts ticking immediately after the graphic is rendered. 
-        /// This field may be used in conjunction with the User Input Flag field. 
         /// </summary>
-        public int? FrameDelay { get; set; }
+        public int FrameDelay { get; set; }
 
         /// <summary>
         /// Gets or sets the resolution of the image in x- direction. It is defined as 
@@ -240,6 +239,8 @@ namespace ImageProcessor
         /// <value>A list of image properties.</value>
         public IList<ImageProperty> Properties { get; } = new List<ImageProperty>();
 
+        internal IImageDecoder Decoder { get; set; }
+
         /// <summary>
         /// Loads the image from the given stream.
         /// </summary>
@@ -279,7 +280,8 @@ namespace ImageProcessor
                         IImageDecoder decoder = decoders.FirstOrDefault(x => x.IsSupportedFileFormat(header));
                         if (decoder != null)
                         {
-                            decoder.Decode(this, stream);
+                            this.Decoder = decoder;
+                            this.Decoder.Decode(this, stream);
                             return;
                         }
                     }

src/ImageProcessor/ImageBase.cs

@@ -40,8 +40,8 @@ namespace ImageProcessor
         /// </exception>
         protected ImageBase(int width, int height)
         {
-            Guard.MustBeGreaterThan(width, 0, "width");
-            Guard.MustBeGreaterThan(height, 0, "height");
+            Guard.MustBeGreaterThan(width, 0, nameof(width));
+            Guard.MustBeGreaterThan(height, 0, nameof(height));
 
             this.Width = width;
             this.Height = height;

tests/ImageProcessor.Tests/Colors/ColorConversionTests.cs

@@ -88,7 +88,7 @@ namespace ImageProcessor.Tests
         }
 
         /// <summary>
-        /// Tests the implicit conversion from <see cref="YCbCr"/> to <see cref="Bgra"/>.
+        /// Tests the implicit conversion from <see cref="Bgra"/> to <see cref="Hsv"/>.
         /// </summary>
         [Fact]
         [SuppressMessage("StyleCop.CSharp.NamingRules", "SA1305:FieldNamesMustNotUseHungarianNotation",
@@ -128,6 +128,9 @@ namespace ImageProcessor.Tests
             Assert.Equal(80, hsv3.V, 1);
         }
 
+        /// <summary>
+        /// Tests the implicit conversion from <see cref="Hsv"/> to <see cref="Bgra"/>.
+        /// </summary>
         [Fact]
         public void HsvToBgr()
         {