function BmpToString(Bmp: TBitmap): string;var
  BinStream:TMemoryStream;
  StrStream: TStringStream;
  s: string;
begin
  BinStream := TMemoryStream.Create;
  try
    StrStream := TStringStream.Create(s);
    try
      Bmp.SaveToStream(BinStream);
      BinStream.Seek(0, soFromBeginning);      ObjectBinaryToText(BinStream, StrStream); 到这里出错。不知是为什么
    
      StrStream.Seek(0, soFromBeginning);
      Result:= StrStream.DataString;
    finally
      StrStream.Free;
    end;
  finally
    BinStream.Free
  end;
end;
那个S变量如何付值。