用TImageList动态画透明图片

procedure TForm1.Button1Click(Sender: TObject);
var
  bm : TBitmap;
  il : TImageList;
begin
  bm := TBitmap.Create;
  bm.LoadFromFile('C:DownLoadTEST.BMP');
  il := TImageList.CreateSize(bm.Width,
                              bm.Height);
  il.DrawingStyle := dsTransparent;
  il.Masked := true;
  il.AddMasked(bm, clRed);
  il.Draw(Form1.Canvas, 0, 0, 0);
  bm.Free;
  il.Free;
end;