//加边框
try
{
  Bitmap Backbmp = new Bitmap(@"" + Path);
  float w = (float)(Backbmp.Width * 0.2);
  using (Graphics g = Graphics.FromImage(Backbmp))
  {
    using (Brush brush = new SolidBrush(Color.FromArgb(0, 156, 255)))
    {
      using (Pen pen = new Pen(brush, w))
      {
        pen.DashStyle = DashStyle.Custom;
        g.DrawRectangle(pen, new Rectangle(0, 0, Math.Abs(Backbmp.Width), Math.Abs(Backbmp.Height)));
        g.Dispose();
        pic.BackgroundImage = Backbmp;
      }
    }
  }
}
catch (Exception)
{
}
//加椭圆
try
{
  Bitmap Backbmp = new Bitmap(@"" + Path);
  float w = (float)(Backbmp.Width * 0.2);
  using (Graphics g = Graphics.FromImage(Backbmp))
  {
    using (Brush brush = new SolidBrush(Color.FromArgb(0, 156, 255)))
    {
      using (Pen pen = new Pen(brush, w))
      {
        pen.DashStyle = DashStyle.Custom;
        g.DrawEllipse(pen, new Rectangle(0, 0, Math.Abs(Backbmp.Width), Math.Abs(Backbmp.Height)));
        g.Dispose();
        pic.BackgroundImage = Backbmp;
      }
    }
  }
}
catch (Exception)
{
}