/// <summary>
/// 从文件数据流中读取图形控制扩展(Graphic Control Extension)
/// </summary>
/// <param name="stream"></param>
/// <returns></returns>
internal LogicalScreenDescriptor GetLCD(Stream stream)
{
LogicalScreenDescriptor lcd = new LogicalScreenDescriptor();
lcd.Width = ReadShort();
lcd.Height = ReadShort();
lcd.Packed = (byte)Read();
lcd.GlobalColorTableFlag = ((lcd.Packed & 0x80) >> 7) == 1;
lcd.ColorResoluTion = (byte)((lcd.Packed & 0x60) >> 5);
lcd.SortFlag = (byte)(lcd.Packed & 0x10) >> 4;
lcd.GlobalColorTableSize = 2 << (lcd.Packed & 0x07);
lcd.BgColorIndex = (byte)Read();
lcd.PixcelAspect = (byte)Read();
return(lcd);
}
/// <summary>
/// 写逻辑屏幕标识符
/// </summary>
/// <param name="lsd"></param>
internal void WriteLSD(LogicalScreenDescriptor lsd)
{
WriteBytes(lsd.GetBuffer());
}