C#使用iTextSharp添加PDF水印

/// <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 = 50;//设置字体大小        int span = 40;//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 + 1;        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 = 0;        string spanString = " ";//水平位移        for (int i = 1; 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 = 0; w < widthNumber; w++)          {            for (int h = 1; 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 = 0; 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;      }    }