private void ReadLogicalScreenDescriptor()
{
byte[] buffer = new byte[7];
_stream.Read(buffer, 0, buffer.Length);
byte packed = buffer[4];
_logicalScreenDescriptor = new GifLogicalScreenDescriptor();
_logicalScreenDescriptor.Width = BitConverter.ToInt16(buffer, 0);
_logicalScreenDescriptor.Height = BitConverter.ToInt16(buffer, 2);
_logicalScreenDescriptor.Background = buffer[5];
_logicalScreenDescriptor.GlobalColorTableFlag = ((packed & 0x80) >> 7) == 1;
_logicalScreenDescriptor.GlobalColorTableSize = 2 << (packed & 0x07);
}
