uses
jpeg;

procedure TForm1.BitBtn1Click(Sender: TObject);
var
  pict : TPicture;
begin
 pict := TPicture.Create;
  try
    pict.LoadFromFile('D:\Projets Delphi\Dimensions jpeg\Test.jpg');
    LabeledEdit1.Text:=IntToStr(pict.Width);
    LabeledEdit2.Text:=IntToStr(pict.Height);
  finally
    pict.Free;
  end;
end;