C#添加文字水印

使用的是iTextSharp添加PDF水印，由于是接口动态生成PDF，所以采用的是全部是内存流的形式，而且水印是平铺是。iTextSharp版本是5.5

 /// <summary>
         /// 添加倾斜水印
         /// </summary>
         /// <param name="pdfStream">pdf文件流</param>
         /// <param name="waterMarkName">水印字符串</param>
         /// <param name="width">页面宽度</param>
         /// <param name="height">页面高度</param>
         public MemoryStream SetWaterMark(MemoryStream pdfStream, string waterMarkName, float width, float height)
         {
             try
             {
                 int fontSize = ;//设置字体大小
                 int span = ;//设置垂直位移
                 MemoryStream outStream = new MemoryStream();
                 PdfReader pdfReader = new PdfReader(pdfStream);
                 PdfStamper pdfStamper = new PdfStamper(pdfReader, outStream);
                 pdfStamper.Writer.CloseStream = false;
                 int total = pdfReader.NumberOfPages + ;
                 PdfContentByte content;
                 BaseFont font = BaseFont.CreateFont(@"C:\WINDOWS\Fonts\STCAIYUN.TTF", BaseFont.IDENTITY_H, BaseFont.EMBEDDED);//华文云彩字体
                 PdfGState gs = new PdfGState();
                 gs.FillOpacity = 0.15f;//透明度
                 int waterMarkNameLenth = waterMarkName.Length;
                 char c;
                 int rise = ;
                 string spanString = " ";//水平位移
                 for (int i = ; i < total; i++)
                 {
                     rise = waterMarkNameLenth * span;
                     content = pdfStamper.GetOverContent(i);//在内容上方加水印
                                                            //content = pdfStamper.GetUnderContent(i);//在内容下方加水印
                     content.SetGState(gs);
                     content.BeginText();
                     content.SetColorFill(BaseColor.GREEN);
                     content.SetFontAndSize(font, fontSize);
                     int heightNumbert = (int)Math.Ceiling((decimal)height / (decimal)rise);//垂直重复的次数，进一发
                     int panleWith = (fontSize + span) * waterMarkNameLenth;
                     int widthNumber = (int)Math.Ceiling((decimal)width / (decimal)panleWith);//水平重复次数

                     // 设置水印文字字体倾斜 开始
                     for (int w = ; w < widthNumber; w++)
                     {
                         for (int h = ; h <= heightNumbert; h++)
                         {
                             int yleng = rise * h;
                             content.SetTextMatrix(w * panleWith, yleng);//x,y设置水印开始的绝对左边，以左下角为x，y轴的起点
                             for (int k = ; k < waterMarkNameLenth; k++)
                             {
                                 content.SetTextRise(yleng);//指定的y轴值处添加
                                 c = waterMarkName[k];
                                 content.ShowText(c + spanString);
                                 yleng -= span;
                             }
                         }
                     }
                     content.EndText();
                 }
                 if (pdfStamper != null)
                     pdfStamper.Close();

                 if (pdfReader != null)
                     pdfReader.Close();

                 return outStream;
             }
             catch (Exception ex)
             {
                 throw ex;
             }
         }