gifdecoder.cs

gif图像处理 包括对多帧gif动画的缩放

#region Copyright & License
/*----------------------------------------------------------------
// Copyright (C) 2008 jillzhang 版权所有。 
//  
// 文件名：GifDecoder.cs    使用请保留版权信息  
// 文件功能描述： 更多信息请访问 http://jillzhang.cnblogs.com
// 
// 创建标识：jillzhang 
// 修改标识：
// 修改描述：
//
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//----------------------------------------------------------------*/
/*-------------------------New BSD License ------------------
 Copyright (c) 2008, jillzhang
All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

* Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

* Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

* Neither the name of jillzhang nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
 */
#endregion

using System;
using System.Collections.Generic;
using System.Text;
using System.IO;
using System.Drawing;
using System.Drawing.Imaging;
using System.Collections;

namespace Jillzhang.GifUtility
{
    #region 类GifDecoder-gif文件解码类
    /// <summary>
    /// GIF图像文件的解码器
    /// </summary>
    internal class GifDecoder
    {      
        #region 私有方法，用于类内部使用     
        static void ReadImage(StreamHelper streamHelper, Stream fs, GifImage gifImage, List<GraphicEx> graphics, int frameCount)
        {
            ImageDescriptor imgDes = streamHelper.GetImageDescriptor(fs);
            GifFrame frame = new GifFrame();
            frame.ImageDescriptor = imgDes;
            frame.LocalColorTable = gifImage.GlobalColorTable;
            if (imgDes.LctFlag)
            {
                frame.LocalColorTable = streamHelper.ReadByte(imgDes.LctSize*3);
            }
            LZWDecoder lzwDecoder = new LZWDecoder(fs);
            int dataSize = streamHelper.Read();
            frame.ColorDepth = dataSize;        
            byte[] piexel = lzwDecoder.DecodeImageData(imgDes.Width, imgDes.Height, dataSize);
            frame.IndexedPixel = piexel;
            int blockSize = streamHelper.Read();
            DataStruct data = new DataStruct(blockSize, fs);         
            GraphicEx graphicEx = graphics[frameCount];
            frame.GraphicExtension = graphicEx;        
            Bitmap img = GetImageFromPixel(piexel, frame.Palette, imgDes.InterlaceFlag, imgDes.Width, imgDes.Height);
            frame.Image = img;          
            gifImage.Frames.Add(frame);
        }
        static Bitmap GetImageFromPixel(byte[] pixel, Color32[] colorTable, bool interlactFlag, int iw, int ih)
        {
            Bitmap img = new Bitmap(iw, ih);           
            BitmapData bmpData = img.LockBits(new Rectangle(0, 0, iw, ih), ImageLockMode.ReadWrite, img.PixelFormat);
            unsafe
            {
                Color32* p = (Color32*)bmpData.Scan0.ToPointer();
                Color32* tempPointer = p;
                int offSet = 0;
                if (interlactFlag)
                {
                    #region 交织存储模式
                    int i = 0;
                    int pass = 0;//当前通道            
                    while (pass < 4)
                    {
                        //总共有4个通道
                        if (pass == 1)
                        {
                            p = tempPointer;
                            p += (4 * iw );
                            offSet += 4 * iw;
                        }
                        else if (pass == 2)
                        {
                            p = tempPointer;
                            p += (2 * iw );
                            offSet += 2 * iw;
                        }
                        else if (pass == 3)
                        {
                            p = tempPointer;
                            p += (1 * iw);
                            offSet += 1 * iw;
                        }
                        int rate = 2;
                        if (pass == 0 | pass == 1)
                        {
                            rate = 8;
                        }
                        else if (pass == 2)
                        {
                            rate = 4;
                        }
                        while (i < pixel.Length)
                        {                         
                            *p++ = colorTable[pixel[i++]];                          
                            offSet++;
                            if (i % (iw) == 0)
                            {
                                p += (iw * (rate - 1));
                                offSet += (iw * (rate - 1));
                                if ( offSet  >= pixel.Length)
                                {
                                    pass++;
                                    offSet = 0;
                                    break;
                                }                               
                            }                        
                        }
                    }
                    #endregion
                }
                else
                {
                    int i = 0;
                    for (i = 0; i < pixel.Length; )
                    {                        
                        *p++ = colorTable[pixel[i++]];   
                    }
                }
            }
            img.UnlockBits(bmpData);  
            return img;
        }
        #endregion

        #region 对gif图像文件进行解码
        /// <summary>
        /// 对gif图像文件进行解码
        /// </summary>
        /// <param name="gifPath">gif文件路径</param>
        internal static GifImage Decode(string gifPath)
        {
            FileStream fs=null;
            StreamHelper streamHelper=null;
            GifImage gifImage = new GifImage();
            List<GraphicEx> graphics = new List<GraphicEx>();        
            int frameCount = 0;
            try
            {
                fs = new FileStream(gifPath,FileMode.Open);
                streamHelper = new StreamHelper(fs);
                //读取文件头
                gifImage.Header = streamHelper.ReadString(6);
                //读取逻辑屏幕标示符
                gifImage.LogicalScreenDescriptor = streamHelper.GetLCD(fs);  
                if (gifImage.LogicalScreenDescriptor.GlobalColorTableFlag)
                {
                    //读取全局颜色列表
                    gifImage.GlobalColorTable = streamHelper.ReadByte(gifImage.LogicalScreenDescriptor.GlobalColorTableSize * 3);
                }
                int nextFlag = streamHelper.Read();
                while (nextFlag != 0)
                {
                    if (nextFlag == GifExtensions.ImageLabel)
                    {
                        ReadImage(streamHelper, fs, gifImage, graphics, frameCount);
                        frameCount++;
                    }
                    else if (nextFlag == GifExtensions.ExtensionIntroducer)
                    {
                        int gcl = streamHelper.Read();
                        switch (gcl)
                        {
                            case GifExtensions.GraphicControlLabel:
                                {
                                    GraphicEx graphicEx = streamHelper.GetGraphicControlExtension(fs);
                                    graphics.Add(graphicEx);
                                    break;
                                }
                            case GifExtensions.CommentLabel:
                                {
                                    CommentEx comment = streamHelper.GetCommentEx(fs);
                                    gifImage.CommentExtensions.Add(comment);
                                    break;
                                }
                            case GifExtensions.ApplicationExtensionLabel:
                                {
                                    ApplicationEx applicationEx = streamHelper.GetApplicationEx(fs);
                                    gifImage.ApplictionExtensions.Add(applicationEx);
                                    break;
                                }
                            case GifExtensions.PlainTextLabel:
                                {
                                    PlainTextEx textEx = streamHelper.GetPlainTextEx(fs);
                                    gifImage.PlainTextEntensions.Add(textEx);
                                    break;
                                }
                        }
                    }
                    else if (nextFlag == GifExtensions.EndIntroducer)
                    {
                        //到了文件尾
                        break;
                    }
                    nextFlag = streamHelper.Read();
                }
            }
            catch
            {
                throw;
            }
            finally
            {
                fs.Close();
            }
            return gifImage;
        }     
        #endregion    
    }
    #endregion
}