ASP.NET 2.0,C#----图像特效处理

              graphics = Graphics.FromImage(bitmap);
              graphics.DrawString(log, new Font("宋体", 16), System.Drawing.Brushes.GreenYellow, new PointF(bitmap.Width / 2 - (log.Length) * 5, bitmap.Height / 2));
              try
              {
                  bitmap.Save(Server.MapPath("./_Log.jpg"), System.Drawing.Imaging.ImageFormat.Jpeg);
                  MessageShow("已经生成水印图片，路径为" + @Server.MapPath("./_log.jpg").Replace("", ""));

              }
              catch (Exception ex)
              {
                  MessageShow("生成图片错误！" + ex.Message);
                  throw;
              }
              graphics.Dispose();
              bitmap.Dispose();
          }
          private void MessageShow(string msg)
          {
              Page.ClientScript.RegisterStartupScript(Page.GetType(), "Message", string.Format(Message, msg));

          }
          //放大X*X倍
          protected void btnBig_Click(object sender, EventArgs e)
          {
              int i = int.Parse(txtBig.Text.Trim());
              System.Drawing.Image img = System.Drawing.Image.FromFile(path);
              bitmap = new Bitmap(img.Width * i, img.Height * i);
              graphics = Graphics.FromImage(bitmap);
              graphics.DrawImage(img, 0, 0, img.Width * i, img.Height * i);