请问我的读取部分的代码有什么问题?

Question

总是在从DBF文件中读出JPEG图片时出问题,JPEG ERROR #50?!我可是用TBLOBFIELD.LOADFROMFILE()的方法直接保存JPEG图片的.//读取已保存的JPEG图片
procedure TForm1.DataSource1DataChange(Sender: TObject; Field: TField);
var
  tmp: tblobstream;tmpjpg: tjpegimage;
begin
  if not tblobfield(table1.fieldbyname('photo')).IsNull then
    begin
    tmp:=TBlobStream.Create(TBlobField(Table1.FieldbyName('photo')), bmRead);
    tmpjpg:= TJPEGImage.Create;
    tmp.Position:=0;
    //下面这句出错 JPEG ERROR #50
    tmpjpg.LoadFromStream(tmp);
    Image1.Picture.Assign(tmpjpg);
    tmp.free;
    tmpjpg.free;
  end
else
  image1.picture:=nil;end;//查找JPEG图片并用TIMAGE显示
procedure TForm1.Button1Click(Sender: TObject);
begin
  if openpicturedialog1.Execute then
    begin
    image1.Picture.LoadFromFile(openpicturedialog1.filename);
    button2.enabled:=true;
    end;
end;//保存JPEG图片
procedure TForm1.Button2Click(Sender: TObject);
var
  tmp: tmemorystream;
begin
  tmp:=tmemorystream.create;
  tmp.LoadFromFile(openpicturedialog1.filename);
  tmp.position:=0;
  table1.Edit;
  tblobfield(table1.FieldByName('photo')).LoadFromstream(tmp);
  tmp.free;
end;

Answer 1

temp: TStringStream;
tmp:=TBlobStream.Create(TBlobField(Table1.FieldbyName('photo')), bmRead);
 改一下；
temp := TStringStream.Create('');
TBlobField(TABLE1.FieldByName('PHOTO')).SaveToStream(temp);

Answer 2

table1.Edit;
  tblobfield(table1.FieldByName('photo')).LoadFromstream(tmp);
table1.post;////////没有保存
  tmp.free;
end;

Answer 3

tmp2: TStream; tmp2:= Table1.CreateBlobStream(Table1.FieldByName('photo'), bmReadWrite);
    try
      tmp2.CopyFrom(tmp, tmp.Size);
      Table1.Post;
    finally
      tmp2.Free;
    end;