/// <summary>
/// 从文件流中读取应用程序扩展块
/// </summary>
/// <param name="stream"></param>
/// <returns></returns>
internal ApplicationEx GetApplicationEx(Stream stream)
{
ApplicationEx appEx = new ApplicationEx();
int blockSize = Read();
if (blockSize != ApplicationEx.BlockSize)
{
throw new Exception("数据格式错误！");
}
appEx.ApplicationIdentifier = ReadChar(8);
appEx.ApplicationAuthenticationCode = ReadChar(3);
int nextFlag = Read();
appEx.Datas = new List <DataStruct>();
while (nextFlag != 0)
{
DataStruct data = new DataStruct(nextFlag, stream);
appEx.Datas.Add(data);
nextFlag = Read();
}
return(appEx);
}
public static GifImage Decode(Stream fs)
{
StreamHelper streamHelper = null;
GifImage gifImage = new GifImage();
List <GraphicEx> graphics = new List <GraphicEx>();
int frameCount = 0;
streamHelper = new StreamHelper(fs);
gifImage.Header = streamHelper.ReadString(6);
gifImage.LogicalScreenDescriptor = streamHelper.GetLCD(fs);
if (gifImage.LogicalScreenDescriptor.GlobalColorTableFlag)
{
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)
{
break;
}
nextFlag = streamHelper.Read();
}
return(gifImage);
}