delphi - 来自 EncodeBase64 和 TIDEncoderMime.EncodeStream 的不同字符串长度

Question

在以下代码片段中，方法 1 导致 showmessage 显示 10048，而方法 2 和 3 显示 9792。哪种方法提供正确的编码以供在 XML 节点中使用？磁盘上的文件大小为 7343。谢谢

DrawingField: AnsiString;
PicStream := TMemoryStream.Create;
encoder := TidEncoderMIME.Create(nil);
StringStream := TStringStream.Create('');
try
  Image1.Picture.LoadFromFile('Ryan.jpg');
  Image1.Picture.Graphic.SaveToStream(PicStream);

  {$ifdef METHOD1}
  DrawingField := EncodeBase64(PicStream.Memory, PicStream.Size);
  {$endif}
  {$ifdef METHOD2}
  PicStream.Position := 0;
  encoder.EncodeStream(PicStream, StringStream);
  DrawingField := StringStream.DataString;
  {$endif}
  {$ifdef METHOD3}
  PicStream.Position := 0;
  DrawingField := encoder.EncodeStream(PicStream, PicStream.Size);
  // SetString(DrawingField, PAnsiChar(PicStream.Memory), PicStream.Size);
  {$endif}

  ShowMessage(IntToStr(Length(DrawingField))); // 1 = 10048 2/3 = 9792
finally
  encoder.Free;
  PicStream.Free;
  StringStream.Free;
end;