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@ -1,8 +1,27 @@ |
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// --------------------------------------------------------------------------------------------------------------------
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// <copyright file="GifEncoder.cs" company="James South">
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// Copyright (c) James South.
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// Licensed under the Apache License, Version 2.0.
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// </copyright>
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// <summary>
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// Encodes multiple images as an animated gif to a stream.
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// <remarks>
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// Always wire this up in a using block.
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// Disposing the encoder will complete the file.
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// Uses default .NET GIF encoding and adds animation headers.
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// </remarks>
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// </summary>
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// --------------------------------------------------------------------------------------------------------------------
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namespace ImageProcessor.Imaging |
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{ |
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#region Using
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using System; |
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using System.Drawing; |
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using System.Drawing.Imaging; |
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using System.IO; |
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using System.Linq; |
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#endregion
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/// <summary>
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/// Encodes multiple images as an animated gif to a stream.
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@ -14,25 +33,93 @@ namespace ImageProcessor.Imaging |
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/// </summary>
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public class GifEncoder : IDisposable |
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{ |
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#region Fields
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private const string FileType = "GIF"; |
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private const string FileVersion = "89a"; |
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private const byte FileTrailer = 0x3b; |
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#region Constants
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/// <summary>
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/// The application block size.
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/// </summary>
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private const byte ApplicationBlockSize = 0x0b; |
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/// <summary>
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/// The application extension block identifier.
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/// </summary>
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private const int ApplicationExtensionBlockIdentifier = 0xff21; |
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private const byte ApplicationBlockSize = 0x0b; |
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/// <summary>
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/// The application identification.
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/// </summary>
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private const string ApplicationIdentification = "NETSCAPE2.0"; |
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/// <summary>
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/// The file trailer.
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/// </summary>
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private const byte FileTrailer = 0x3b; |
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/// <summary>
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/// The file type.
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/// </summary>
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private const string FileType = "GIF"; |
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/// <summary>
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/// The file version.
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/// </summary>
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private const string FileVersion = "89a"; |
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/// <summary>
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/// The graphic control extension block identifier.
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/// </summary>
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private const int GraphicControlExtensionBlockIdentifier = 0xf921; |
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/// <summary>
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/// The graphic control extension block size.
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/// </summary>
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private const byte GraphicControlExtensionBlockSize = 0x04; |
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/// <summary>
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/// The source color block length.
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/// </summary>
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private const long SourceColorBlockLength = 768; |
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/// <summary>
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/// The source color block position.
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/// </summary>
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private const long SourceColorBlockPosition = 13; |
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/// <summary>
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/// The source global color info position.
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/// </summary>
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private const long SourceGlobalColorInfoPosition = 10; |
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private const long SourceGraphicControlExtensionPosition = 781; |
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/// <summary>
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/// The source graphic control extension length.
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/// </summary>
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private const long SourceGraphicControlExtensionLength = 8; |
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private const long SourceImageBlockPosition = 789; |
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/// <summary>
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/// The source graphic control extension position.
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/// </summary>
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private const long SourceGraphicControlExtensionPosition = 781; |
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/// <summary>
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/// The source image block header length.
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/// </summary>
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private const long SourceImageBlockHeaderLength = 11; |
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private const long SourceColorBlockPosition = 13; |
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private const long SourceColorBlockLength = 768; |
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/// <summary>
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/// The source image block position.
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/// </summary>
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private const long SourceImageBlockPosition = 789; |
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#endregion
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#region Fields
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/// <summary>
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/// The stream.
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/// </summary>
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private Stream inputStream; |
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/// <summary>
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/// The height.
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/// </summary>
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private int? height; |
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/// <summary>
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/// A value indicating whether this instance of the given entity has been disposed.
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@ -46,9 +133,103 @@ namespace ImageProcessor.Imaging |
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/// life in the Garbage Collector.
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/// </remarks>
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private bool isDisposed; |
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/// <summary>
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/// The is first image.
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/// </summary>
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private bool isFirstImage = true; |
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/// <summary>
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/// The repeat count.
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/// </summary>
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private int? repeatCount; |
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/// <summary>
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/// The width.
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/// </summary>
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private int? width; |
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#endregion
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#region Constructors and Destructors
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/// <summary>
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/// Initializes a new instance of the <see cref="GifEncoder"/> class.
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/// </summary>
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/// <param name="stream">
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/// The stream that will be written to.
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/// </param>
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/// <param name="width">
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/// Sets the width for this gif or null to use the first frame's width.
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/// </param>
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/// <param name="height">
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/// Sets the height for this gif or null to use the first frame's height.
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/// </param>
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/// <param name="repeatCount">
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/// The number of times to repeat the animation.
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/// </param>
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public GifEncoder(Stream stream, int? width = null, int? height = null, int? repeatCount = null) |
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{ |
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this.inputStream = stream; |
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this.width = width; |
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this.height = height; |
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this.repeatCount = repeatCount; |
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} |
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/// <summary>
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/// Finalizes an instance of the <see cref="GifEncoder"/> class.
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/// </summary>
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/// <remarks>
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/// Use C# destructor syntax for finalization code.
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/// This destructor will run only if the Dispose method
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/// does not get called.
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/// It gives your base class the opportunity to finalize.
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/// Do not provide destructors in types derived from this class.
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/// </remarks>
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~GifEncoder() |
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{ |
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// Do not re-create Dispose clean-up code here.
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// Calling Dispose(false) is optimal in terms of
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// readability and maintainability.
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this.Dispose(false); |
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} |
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#endregion
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#region Properties
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/// <summary>
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/// Gets or sets the frame delay.
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/// </summary>
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public TimeSpan FrameDelay { get; set; } |
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#endregion
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#region IDisposable Members
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#region Public Methods and Operators
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/// <summary>
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/// Adds a frame to the gif.
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/// </summary>
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/// <param name="frame">
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/// The <see cref="GifFrame"/> containing the image.
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/// </param>
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public void AddFrame(GifFrame frame) |
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{ |
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using (MemoryStream gifStream = new MemoryStream()) |
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{ |
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frame.Image.Save(gifStream, ImageFormat.Gif); |
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if (this.isFirstImage) |
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{ |
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// Steal the global color table info
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this.WriteHeaderBlock(gifStream, frame.Image.Width, frame.Image.Height); |
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} |
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this.WriteGraphicControlBlock(gifStream, frame.Delay); |
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this.WriteImageBlock(gifStream, !this.isFirstImage, frame.X, frame.Y, frame.Image.Width, frame.Image.Height); |
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} |
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this.isFirstImage = false; |
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} |
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public Image Save() |
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{ |
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} |
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/// <summary>
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/// Disposes the object and frees resources for the Garbage Collector.
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/// </summary>
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@ -63,11 +244,15 @@ namespace ImageProcessor.Imaging |
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// from executing a second time.
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GC.SuppressFinalize(this); |
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} |
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#endregion
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#region Methods
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/// <summary>
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/// Disposes the object and frees resources for the Garbage Collector.
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/// </summary>
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/// <param name="disposing">If true, the object gets disposed.</param>
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/// <param name="disposing">
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/// If true, the object gets disposed.
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/// </param>
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protected virtual void Dispose(bool disposing) |
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{ |
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if (this.isDisposed) |
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@ -78,18 +263,21 @@ namespace ImageProcessor.Imaging |
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if (disposing) |
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{ |
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// Dispose of any managed resources here.
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//if (this.Image != null)
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//{
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// // Dispose of the memory stream from Load and the image.
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// if (this.inputStream != null)
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// {
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// this.inputStream.Dispose();
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// this.inputStream = null;
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// }
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// this.Image.Dispose();
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// this.Image = null;
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//}
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// Complete Application Block
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this.WriteByte(0); |
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// Complete File
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this.WriteByte(FileTrailer); |
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// Pushing data
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this.inputStream.Flush(); |
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// Dispose of the memory stream from Load and the image.
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if (this.inputStream != null) |
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{ |
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this.inputStream.Dispose(); |
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this.inputStream = null; |
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} |
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} |
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// Call the appropriate methods to clean up
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@ -97,6 +285,183 @@ namespace ImageProcessor.Imaging |
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// Note disposing is done.
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this.isDisposed = true; |
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} |
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/// <summary>
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/// Writes the header block of the animated gif to the stream.
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/// </summary>
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/// <param name="sourceGif">
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/// The source gif.
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/// </param>
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/// <param name="w">
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/// The width of the image.
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/// </param>
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/// <param name="h">
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/// The height of the image.
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/// </param>
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private void WriteHeaderBlock(Stream sourceGif, int w, int h) |
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{ |
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int count = this.repeatCount.GetValueOrDefault(0); |
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// File Header
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this.WriteString(FileType); |
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this.WriteString(FileVersion); |
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this.WriteShort(this.width.GetValueOrDefault(w)); // Initial Logical Width
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this.WriteShort(this.height.GetValueOrDefault(h)); // Initial Logical Height
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sourceGif.Position = SourceGlobalColorInfoPosition; |
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this.WriteByte(sourceGif.ReadByte()); // Global Color Table Info
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this.WriteByte(0); // Background Color Index
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this.WriteByte(0); // Pixel aspect ratio
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this.WriteColorTable(sourceGif); |
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// The different browsers interpret the spec differently when adding a loop.
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// If the loop count is one IE and FF < 3 (incorrectly) loop an extra number of times.
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// Removing the Netscape header should fix this.
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if (count != 1) |
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{ |
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// Application Extension Header
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this.WriteShort(ApplicationExtensionBlockIdentifier); |
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this.WriteByte(ApplicationBlockSize); |
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this.WriteString(ApplicationIdentification); |
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this.WriteByte(3); // Application block length
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this.WriteByte(1); |
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this.WriteShort(this.repeatCount.GetValueOrDefault(0)); // Repeat count for images.
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this.WriteByte(0); // Terminator
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} |
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} |
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/// <summary>
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/// The write byte.
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/// </summary>
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/// <param name="value">
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/// The value.
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/// </param>
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private void WriteByte(int value) |
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{ |
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this.inputStream.WriteByte(Convert.ToByte(value)); |
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} |
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/// <summary>
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/// The write color table.
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/// </summary>
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/// <param name="sourceGif">
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/// The source gif.
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/// </param>
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private void WriteColorTable(Stream sourceGif) |
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{ |
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sourceGif.Position = SourceColorBlockPosition; // Locating the image color table
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byte[] colorTable = new byte[SourceColorBlockLength]; |
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sourceGif.Read(colorTable, 0, colorTable.Length); |
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this.inputStream.Write(colorTable, 0, colorTable.Length); |
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} |
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/// <summary>
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/// The write graphic control block.
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/// </summary>
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/// <param name="sourceGif">
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/// The source gif.
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/// </param>
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/// <param name="frameDelay">
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/// The frame delay.
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/// </param>
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private void WriteGraphicControlBlock(Stream sourceGif, int frameDelay) |
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{ |
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sourceGif.Position = SourceGraphicControlExtensionPosition; // Locating the source GCE
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byte[] blockhead = new byte[SourceGraphicControlExtensionLength]; |
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sourceGif.Read(blockhead, 0, blockhead.Length); // Reading source GCE
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this.WriteShort(GraphicControlExtensionBlockIdentifier); // Identifier
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this.WriteByte(GraphicControlExtensionBlockSize); // Block Size
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this.WriteByte(blockhead[3] & 0xf7 | 0x08); // Setting disposal flag
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this.WriteShort(Convert.ToInt32(frameDelay / 10)); // Setting frame delay
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this.WriteByte(blockhead[6]); // Transparent color index
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this.WriteByte(0); // Terminator
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} |
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/// <summary>
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/// The write image block.
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/// </summary>
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/// <param name="sourceGif">
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/// The source gif.
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/// </param>
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/// <param name="includeColorTable">
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/// The include color table.
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/// </param>
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/// <param name="x">
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/// The x position to write the image block.
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/// </param>
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/// <param name="y">
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/// The y position to write the image block.
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/// </param>
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/// <param name="h">
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/// The height of the image block.
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/// </param>
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/// <param name="w">
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/// The width of the image block.
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/// </param>
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private void WriteImageBlock(Stream sourceGif, bool includeColorTable, int x, int y, int h, int w) |
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{ |
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sourceGif.Position = SourceImageBlockPosition; // Locating the image block
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byte[] header = new byte[SourceImageBlockHeaderLength]; |
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sourceGif.Read(header, 0, header.Length); |
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this.WriteByte(header[0]); // Separator
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this.WriteShort(x); // Position X
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this.WriteShort(y); // Position Y
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this.WriteShort(h); // Height
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this.WriteShort(w); // Width
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if (includeColorTable) |
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{ |
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// If first frame, use global color table - else use local
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sourceGif.Position = SourceGlobalColorInfoPosition; |
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this.WriteByte(sourceGif.ReadByte() & 0x3f | 0x80); // Enabling local color table
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this.WriteColorTable(sourceGif); |
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} |
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else |
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{ |
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this.WriteByte(header[9] & 0x07 | 0x07); // Disabling local color table
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} |
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this.WriteByte(header[10]); // LZW Min Code Size
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// Read/Write image data
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sourceGif.Position = SourceImageBlockPosition + SourceImageBlockHeaderLength; |
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int dataLength = sourceGif.ReadByte(); |
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while (dataLength > 0) |
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{ |
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byte[] imgData = new byte[dataLength]; |
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sourceGif.Read(imgData, 0, dataLength); |
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this.inputStream.WriteByte(Convert.ToByte(dataLength)); |
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this.inputStream.Write(imgData, 0, dataLength); |
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dataLength = sourceGif.ReadByte(); |
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} |
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this.inputStream.WriteByte(0); // Terminator
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} |
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/// <summary>
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/// The write short.
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/// </summary>
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/// <param name="value">
|
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/// The value.
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/// </param>
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private void WriteShort(int value) |
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{ |
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|
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this.inputStream.WriteByte(Convert.ToByte(value & 0xff)); |
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|
this.inputStream.WriteByte(Convert.ToByte((value >> 8) & 0xff)); |
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} |
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/// <summary>
|
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|
|
/// The write string.
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|
/// </summary>
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|
/// <param name="value">
|
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|
|
/// The value.
|
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|
|
/// </param>
|
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|
|
private void WriteString(string value) |
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|
|
{ |
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|
|
this.inputStream.Write(value.ToArray().Select(c => (byte)c).ToArray(), 0, value.Length); |
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|
} |
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|
#endregion
|
|
|
|
} |
|
|
|
} |
|
|
|
} |
James South
12 years ago