Delphi将图片保存至Sql Server中的小问题？

Question

怎么限制保存图片的大小呢？比如说超过500K的图片就不允许提交。否则数据库太大了，读取也慢。保存图片代码如下，怎么改一下？：
//保存图片
procedure TForm1.btn1Click(Sender: TObject);
begin
  if dlgOpen1.Execute then
    img1.Picture.LoadFromFile(dlgOpen1.FileName);
  qry1.Append;
  qry1.Post;
end;
//提前之前将图片转换为数据流
procedure TForm1.qry1BeforePost(DataSet: TDataSet);
var
  ms: TMemoryStream;
  jpg: TJpegImage;
begin
  ms := TMemoryStream.Create;
  jpg := TJpegImage.Create;
  try
    if img1.Picture.Graphic<>nil then
      begin
        try
          img1.Picture.Graphic.SaveToStream(ms);
        finally
          TBlobField(qry1.FieldByName('pic')).LoadFromStream(ms);
        end;
      end;
  finally
    jpg.Free;
    ms.Free;
  end;
end;

Answer 1

if ms.Size > 500k then
  弹一个提示框

Answer 2

简单点改procedure TForm1.qry1BeforePost(DataSet: TDataSet);
var
  ms: TMemoryStream;
  jpg: TJpegImage;
begin
  ms := TMemoryStream.Create;
  jpg := TJpegImage.Create;
  try
    if img1.Picture.Graphic <>nil then
      begin
        try
          img1.Picture.Graphic.SaveToStream(ms);
//add          
          if ms.size>1024*500 then
          begin
            //do something
          end
          else
            //save to database
//add
        finally
          TBlobField(qry1.FieldByName('pic')).LoadFromStream(ms);
        end;
      end;
  finally
    jpg.Free;
    ms.Free;
  end;
end;

Answer 3

是通过TMemoryStream的Size来判断大小的。