C#实现给图片加边框的方法

  Bitmap bit= new Bitmap(@"" + Path);//给图片加边框
  //Bitmap bit = new Bitmap(Screen.AllScreens[0].Bounds.Size.Width, Screen.AllScreens[0].Bounds.Size.Height);//给当前桌面图加边框
  float w = (float)(bit.Width * 0.2);//边框的宽度，可取任意值
   using (Graphics g = Graphics.FromImage(bit))
   {
       // g.CopyFromScreen(0, 0, 0, 0, Screen.AllScreens[0].Bounds.Size);//抓取背景图
         using (Pen pen = new Pen(Color.White, w))
        {
  　    　//g.DrawRectangle(pen, new Rectangle(0, 0, Screen.AllScreens[0].Bounds.Size.Width, Screen.AllScreens[0].Bounds.Size.Height));//给当前桌面画白框
         //g.DrawRectangle(pen, new Rectangle(0, 0, Math.Abs(bit.Width), Math.Abs(bit.Height)));//加边框
  　　      g.DrawEllipse(pen, new Rectangle(, , Math.Abs(bit.Width), Math.Abs(bit.Height)));//加椭圆边框
           g.Dispose();
         // pic.BackgroundImage = bit;
        }
    }