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);
}
internal CommentEx GetCommentEx(Stream stream)
{
CommentEx cmtEx = new CommentEx();
StreamHelper streamHelper = new StreamHelper(stream);
cmtEx.CommentDatas = new List <string>();
int nextFlag = streamHelper.Read();
cmtEx.CommentDatas = new List <string>();
while (nextFlag != 0)
{
int blockSize = nextFlag;
string data = streamHelper.ReadString(blockSize);
cmtEx.CommentDatas.Add(data);
nextFlag = streamHelper.Read();
}
return(cmtEx);
}
/// <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);
}