private void Read(Stream stream) { this.Signature = GifHelpers.ReadString(stream, 3); if (this.Signature != "GIF") { throw GifHelpers.InvalidSignatureException(this.Signature); } this.Version = GifHelpers.ReadString(stream, 3); if (this.Version != "87a" && this.Version != "89a") { throw GifHelpers.UnsupportedVersionException(this.Version); } this.LogicalScreenDescriptor = GifLogicalScreenDescriptor.ReadLogicalScreenDescriptor(stream); }