Comment mettre une image sur un bouton?

Comment mettre une image sur un bouton?

var
  Bitmap, Bitmap2: TBitmap;
  MyHandle: THandle;
  Rec: TRect;
begin
  Bitmap:=TBitmap.Create;
  Bitmap2:=TBitmap.Create;
  Bitmap2.LoadFromFile('c:\a.bmp');
  Rec:=Rect(2, 2, Button1.Width-2, Button1.Height-2);
  MyHandle:=GetDC(Button1.Handle);
  Bitmap.Canvas.Handle:=MyHandle;
  Bitmap.Canvas.StretchDraw(Rec, Bitmap2);
end;