我用了button ，openpicturedialog，image空间，做了个小小编程，现在我要在image里打开的图片上画线，是单击鼠标左键开始画线，拉动一段距离后，单击右键完成画线，
求高手给个程序代码




procedure TForm1.Button1Click(Sender: TObject);
begin
if openpicturedialog1.Execute then
image1.Picture.LoadFromFile(openpicturedialog1.FileName);
end;