C# -- ITextSharp生成带水印的PDF

   上周按需求需要在系统上实现PDF带水印文档的导出，网上搜了一下发现开源的组件还挺多的，用的比较多的是ITextsharp，Demo也相对较多，就它了！

   （一）首先下载ITextSharp.dll,可在官网上下载：http://sourceforge.net/projects/itextsharp/，本人用了itextsharp-dll-core文件夹下的dll。

   （二）网上有很多类似的Demo和ITextSharp各属性的详细讲解，就不做重复累赘了，可自行百度参考。

   （三）使用过程：在需要的地方调用CreatePDF.Instance.GeneratePDF()即可，详细代码如下：

//要用到的命名空间
    using System.IO;
    using iTextSharp.text;
    using iTextSharp.text.pdf;
    using System.Text;
    using System.Data;
    public class CreatePDF
    {
        private static CreatePDF instance;
        public static CreatePDF GetInstance()
        {
            if (instance == null)
            {
                instance = new CreatePDF();
            }
            return instance;
        }

        private static Document doc;
        private static BaseFont bf = BaseFont.CreateFont(@"C://Windows/Fonts/simsun.ttc,0", BaseFont.IDENTITY_H, BaseFont.EMBEDDED);
        //四种字体
        private static Font fontBig = new Font(bf, 20, Font.BOLD);
        private static Font fontMiddle = new Font(bf, 15, Font.BOLD);
        private static Font fontSmall = new Font(bf, 13, Font.BOLD);
        private static Font fontSmallNoBold = new Font(bf, 13);
        private static float IndentationLeft = 50;//距左边距
        //如果要传参数进来，可自定义
        public void GeneratePDF()
        {
            doc = new Document(PageSize.A4);
            try
            {
                //MemoryStream ms2 = new MemoryStream();
                string fileName = string.Format("数据_{0}.pdf", DateTime.Now.ToString("yyyyMMddHHmmss"));
                string filePath = string.Format("{0}/Resource/{1}", AppDomain.CurrentDomain.BaseDirectory, fileName);
                FileStream fs = new FileStream(filePath, FileMode.Create);//创建临时文件，到时生成好后删除
                PdfWriter writer = PdfWriter.GetInstance(doc, fs);
                writer.CloseStream = false;//把doc内容写入流中
                doc.Open();

                //核心操作
                CreateLine();//生成一条下横线
                CreateEmptyRow(1);//生成一行空行
                AddHeaderTitleContent("表10 已安装工程量明细表");//添加表头
                CreateEmptyRow(1);//生成一行空行
                AddPartnerContent("工程名称", "建设名称", "施工名称", "监理名称");//添加合作单位
                AddPageNumberContent();//添加页码
                CreateEmptyRow(1);//生成一行空行

                #region 生成表格数据
                PdfPTable table = new PdfPTable(6);//6列的table
                //添加表格列头               
                table.SetTotalWidth(new float[] { 50, 200, 60, 60, 100, 100 });
                table.AddCell(GetPdfCell("序号", fontSmallNoBold, Element.ALIGN_CENTER));
                table.AddCell(GetPdfCell("工程量名称", fontSmallNoBold, Element.ALIGN_CENTER));
                table.AddCell(GetPdfCell("单位", fontSmallNoBold, Element.ALIGN_CENTER));
                table.AddCell(GetPdfCell("数量", fontSmallNoBold, Element.ALIGN_CENTER));
                table.AddCell(GetPdfCell("安装地点、路段", fontSmallNoBold, Element.ALIGN_CENTER));
                table.AddCell(GetPdfCell("备注", fontSmallNoBold, Element.ALIGN_CENTER));

                int emptyRow = 20;//如果table的行数小于20行，那么剩余部分显示空白行
                #region 构造数据源
                DataTable tableSource = new DataTable();
                tableSource.Columns.Add(new DataColumn("aa"));
                tableSource.Columns.Add(new DataColumn("bb"));
                tableSource.Columns.Add(new DataColumn("cc"));
                tableSource.Columns.Add(new DataColumn("dd"));
                tableSource.Columns.Add(new DataColumn("ee"));
                for (int i = 0; i < 15; i++)
                {
                    DataRow row = tableSource.NewRow();
                    row["aa"] = "aa";
                    row["bb"] = "bb";
                    row["cc"] = "cc";
                    row["dd"] = "dd";
                    row["ee"] = "ee";
                    tableSource.Rows.Add(row);
                }
                #endregion
                if (tableSource.Rows.Count > 0)
                {
                    emptyRow = emptyRow - tableSource.Rows.Count;//如果为负数，说明不需要生成空白行
                    for (int i = 0; i < tableSource.Rows.Count; i++)
                    {
                        DataRow row = tableSource.Rows[i];
                        table.AddCell(GetPdfCell((i + 1).ToString(), fontSmallNoBold, Element.ALIGN_CENTER));
                        table.AddCell(GetPdfCell(row["aa"].ToString(), fontSmallNoBold, Element.ALIGN_CENTER));
                        table.AddCell(GetPdfCell(row["bb"].ToString(), fontSmallNoBold, Element.ALIGN_CENTER));
                        table.AddCell(GetPdfCell(row["cc"].ToString(), fontSmallNoBold, Element.ALIGN_CENTER));
                        table.AddCell(GetPdfCell(row["dd"].ToString(), fontSmallNoBold, Element.ALIGN_CENTER));
                        table.AddCell(GetPdfCell(row["ee"].ToString(), fontSmallNoBold, Element.ALIGN_CENTER));
                    }
                }
                if (emptyRow > 0)//说明数据源不足20行
                {
                    for (int i = 0; i < emptyRow; i++)
                    {
                        table.AddCell(GetPdfCell(((20 - emptyRow) + i + 1).ToString(), fontSmallNoBold, Element.ALIGN_CENTER));
                        table.AddCell(GetPdfCell("", fontSmallNoBold, Element.ALIGN_CENTER));
                        table.AddCell(GetPdfCell("", fontSmallNoBold, Element.ALIGN_CENTER));
                        table.AddCell(GetPdfCell("", fontSmallNoBold, Element.ALIGN_CENTER));
                        table.AddCell(GetPdfCell("", fontSmallNoBold, Element.ALIGN_CENTER));
                        table.AddCell(GetPdfCell("", fontSmallNoBold, Element.ALIGN_CENTER));
                    }
                }
                doc.Add(table); 
                #endregion

                #region 添加水印
                string waterMarkName = "经度：无  纬度：无  地址：无  验收负责人：无";
                string waterMarkAddr = "广州市天河区";
                if (!string.IsNullOrEmpty(waterMarkAddr))
                {
                    waterMarkName = string.Format("经度：{0}  纬度：{1}  地址：{2}  验收负责人：{3}", "113.211", "23.211", waterMarkAddr, "张三");
                } 
                #endregion
                
                doc.Close();
                MemoryStream ms = new MemoryStream();
                if (fs != null)
                {
                    byte[] bytes = new byte[fs.Length];//定义一个长度为fs长度的字节数组
                    fs.Read(bytes, 0, (int)fs.Length);//把fs的内容读到字节数组中
                    ms.Write(bytes, 0, bytes.Length);//把字节内容读到流中
                    fs.Flush();
                    fs.Close();
                }
                MemoryStream waterMS = SetWaterMark(ms, filePath, waterMarkName);//先生成水印，再删除临时文件
                if (File.Exists(filePath))//判断临时文件是否存在，如果存在则删除
                {
                    File.Delete(filePath);
                    GC.Collect();//回收垃圾
                }
                SendFile(fileName, waterMS);//把PDF文件发送回浏览器
            }
            catch (DocumentException ex)
            {
                throw new Exception(ex.Message);
            }
        }
        #region 生成一条横线
        private static void CreateLine()
        {
            PdfPTable table = new PdfPTable(1);//一个单元格的
            table.TotalWidth = 500;
            PdfPCell cell = new PdfPCell();
            cell.BorderWidthBottom = 0.5f;
            table.AddCell(cell);
            doc.Add(table);
        }
        #endregion

        #region 生成N行空白行
        private static void CreateEmptyRow(int emptyRowNum)
        {
            for (int i = 0; i < emptyRowNum; i++)
            {
                doc.Add(new Paragraph(" "));
            }
        }
        #endregion

        #region 生成标题
        private static void AddHeaderTitleContent(string content)
        {
            Paragraph p = new Paragraph(content, fontMiddle);
            p.IndentationLeft = IndentationLeft;//距离左边距
            doc.Add(p);
        }
        #endregion

        #region 生成合作单位
        private static void AddPartnerContent(string stationName, string constructUnit, string buildUnit, string supervisionUnit)
        {
            fontMiddle.SetStyle(Font.UNDERLINE);//文字下划线
            IndentationLeft = IndentationLeft + 10;

            Paragraph content = new Paragraph();
            content.IndentationLeft = IndentationLeft;
            Chunk chunkName = new Chunk("单项或单位工程名称:", fontSmallNoBold);
            Chunk chunkText = new Chunk(GetEmptyString(25, stationName), fontMiddle);
            content.Add(0, chunkName);
            content.Add(1, chunkText);
            content.Alignment = 3;
            doc.Add(content);

            content = new Paragraph();
            content.IndentationLeft = IndentationLeft;
            chunkName = new Chunk("建设单位名称:", fontSmallNoBold);
            chunkText = new Chunk(GetEmptyString(30, constructUnit), fontMiddle);
            content.Add(0, chunkName);
            content.Add(1, chunkText);
            content.Alignment = 3;
            doc.Add(content);

            content = new Paragraph();
            content.IndentationLeft = IndentationLeft;
            chunkName = new Chunk("施工单位名称:", fontSmallNoBold);
            chunkText = new Chunk(GetEmptyString(30, buildUnit), fontMiddle);
            content.Add(0, chunkName);
            content.Add(1, chunkText);
            content.Alignment = 3;
            doc.Add(content);

            content = new Paragraph();
            content.IndentationLeft = IndentationLeft;
            chunkName = new Chunk("监理单位名称:", fontSmallNoBold);
            chunkText = new Chunk(GetEmptyString(30, supervisionUnit), fontMiddle);
            content.Add(0, chunkName);
            content.Add(1, chunkText);
            content.Alignment = 3;
            doc.Add(content);
        }
        //居中显示内容
        private static string GetEmptyString(int maxlength, string text)
        {
            int padding = (maxlength - text.Length * 2) / 2;
            string empty = string.Empty;
            for (int i = 0; i < padding; i++)
            {
                empty += " ";
            }
            return string.Format("{0}{1}{0}", empty, text);
        }
        #endregion

        #region 生成页码
        private static void AddPageNumberContent()
        {
            var content = new Paragraph("共   页  第   页", fontSmall);
            content.IndentationRight = IndentationLeft + 20;
            content.Alignment = 2;    //居左
            doc.Add(content);
        }
        #endregion

        #region 生成单元格
        private static PdfPCell GetPdfCell(string content, Font font, int horizontalAlignment)
        {
            PdfPCell cell = new PdfPCell(new Paragraph(content, font));
            cell.HorizontalAlignment = horizontalAlignment;//水平位置
            cell.VerticalAlignment = Element.ALIGN_CENTER;//垂直居中
            cell.MinimumHeight = 20;//单元格的最小高度
            return cell;
        }
        #endregion

        #region 生成水印
        private static MemoryStream SetWaterMark(MemoryStream ms, string filePath, string waterMarkName, string waterMarkAddr = null)
        {
            MemoryStream msWater = new MemoryStream();
            PdfReader pdfReader = null;
            PdfStamper pdfStamper = null;
            try
            {
                pdfReader = new PdfReader(filePath);
                pdfStamper = new PdfStamper(pdfReader, msWater);

                int total = pdfReader.NumberOfPages + 1;//获取PDF的总页数
                iTextSharp.text.Rectangle psize = pdfReader.GetPageSize(1);//获取第一页
                float width = psize.Width;//PDF页面的宽度，用于计算水印倾斜
                float height = psize.Height;
                PdfContentByte waterContent;
                BaseFont basefont = BaseFont.CreateFont(@"C:WINDOWSFontsSIMFANG.TTF", BaseFont.IDENTITY_H, BaseFont.EMBEDDED);
                PdfGState gs = new PdfGState();
                for (int i = 1; i < total; i++)
                {
                    waterContent = pdfStamper.GetOverContent(i);//在内容上方加水印
                    //透明度
                    waterContent.SetGState(gs);
                    //开始写入文本
                    waterContent.BeginText();
                    waterContent.SetColorFill(BaseColor.RED);
                    waterContent.SetFontAndSize(basefont, 18);
                    waterContent.SetTextMatrix(0, 0);
                    if (waterMarkAddr == null || waterMarkAddr == "")
                    {
                        waterContent.ShowTextAligned(Element.ALIGN_CENTER, waterMarkName, width / 2, height / 2, 55);
                    }
                    else
                    {
                        waterContent.ShowTextAligned(Element.ALIGN_CENTER, waterMarkName, width / 2, height / 2 + 100, 55);
                        waterContent.ShowTextAligned(Element.ALIGN_CENTER, waterMarkAddr, width / 2, height / 2 - 100, 55);
                    }
                    waterContent.EndText();
                }
            }
            catch (Exception)
            {
                return ms;
            }
            finally
            {
                if (pdfStamper != null)
                    pdfStamper.Close();

                if (pdfReader != null)
                    pdfReader.Close();
            }
            return msWater;
        }
        #endregion

        //-----------------------发送PDF文件回浏览器端----------------------
        public static void SendFile(string fileName, MemoryStream ms, Encoding encoding = null)
        {
            fileName = (fileName + "").Replace(" ", "");
            encoding = encoding ?? Encoding.UTF8;
            if (ms != null && !string.IsNullOrEmpty(fileName))
            {
                System.Web.HttpResponse response = System.Web.HttpContext.Current.Response;
                response.Clear();
                response.Charset = encoding.BodyName;// "utf-8";
                if (!HttpContext.Current.Request.UserAgent.Contains("Firefox") && !HttpContext.Current.Request.UserAgent.Contains("Chrome"))
                {
                    fileName = HttpUtility.UrlEncode(fileName, encoding);
                }
                response.AddHeader("Content-Disposition", "attachment;filename=" + fileName);
                //为了解决打开，导出NPOI生成的xlsx文件时，提示发现不可读取内容。
                if (!(fileName + "").ToLower().EndsWith(".xlsx"))
                {
                    response.AddHeader("Content-Type", "application/octet-stream");
                    response.BinaryWrite(ms.GetBuffer());
                }
                else
                {
                    response.BinaryWrite(ms.ToArray());
                }
                ms.Close();
                ms = null;
                response.Flush();
                response.End();
            }
        }
    }

   （四）总结：

     从代码上，不难看出，普遍用到的标签大多为Document、Paragraph、Table、Cell、Chunck、Font、Element，通过这些标签大概能组合出自己想要的效果，有点类似Html思想。

      a.通过Paragraph、chunck即可显示行元素，若要设置间距或居中等效果，需要熟悉对属性的使用，如设置居中需要Element.ALIGN_CENTER

      b.table操作cell，cell内要添加Paragraph来显示内容，如果需要跨行跨列效果，则可通过cell.Colspan或cell.Rowspan来设置，

      c.实现上不难，如果要达到自己的效果，得多熟悉元素属性的使用和多思考多实践