Detailed explanation of C# code case for adding PDF watermark using iTextSharp

This article mainly introduces in detail the relevant information of C# using iTextSharp to add PDF watermark. It has certain reference value. Interested friends can refer to it

Usage What is used is iTextSharp to add PDF watermarks. Since the interface dynamically generates PDF, it is all in the form of memory streams, and the watermarks are tiled. iTextSharp version is 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 = 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;
      }
    }

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