C#添加文字水印

使用的是iTextSharp添加PDF水印，由於是接口動態生成PDF，所以采用的是全部是內存流的形式，而且水印是平鋪是。iTextSharp版本是5.5

/// <summary>
        /// 添加傾斜水印
        /// </summary>
        /// <param name="pdfStream">pdf文件流</param>
        /// <param name="waterMarkName">水印字符串</param>
        /// <param name="width">頁面寬度</param>
        /// <param name="height">頁面高度</param>
        public MemoryStream SetWaterMark(MemoryStream pdfStream, string waterMarkName, float width, float height)
        {
            try
            {
                int fontSize = 50;//設置字體大小
                int span = 40;//設置垂直位移
                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);//華文雲彩字體
                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);//在內容上方加水印
                                                           //content = pdfStamper.GetUnderContent(i);//在內容下方加水印
                    content.SetGState(gs);
                    content.BeginText();
                    content.SetColorFill(BaseColor.GREEN);
                    content.SetFontAndSize(font, fontSize);
                    int heightNumbert = (int)Math.Ceiling((decimal)height / (decimal)rise);//垂直重復的次數，進一發
                    int panleWith = (fontSize + span) * waterMarkNameLenth;
                    int widthNumber = (int)Math.Ceiling((decimal)width / (decimal)panleWith);//水平重復次數
                   
                    // 設置水印文字字體傾斜 開始 
                    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設置水印開始的絕對左邊，以左下角為x，y軸的起點
                            for (int k = 0; k < waterMarkNameLenth; k++)
                            {
                                content.SetTextRise(yleng);//指定的y軸值處添加
                                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;
            }
        }