iTextSharp之pdfRead（两个文件文本内容的比较，指定页数的pdf截取，水印的添加）

using iTextSharp.text;
using iTextSharp.text.pdf;
using iTextSharp.text.pdf.parser;
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication1
{
    class pdfRead
    {
        /// <summary>
        /// 读取2个pdf的内容判断文件是否相同
        /// </summary>
        /// <param name="filepath"></param>
        /// <param name="filepath2"></param>
        /// <returns></returns>
        public string reading(string filepath, string filepath2)
        {
            try
            {
                PdfReader pdfReader = new PdfReader(filepath);
                PdfReader pdfReader2 = new PdfReader(filepath2);

                int numberOfPages = pdfReader.NumberOfPages;
                int numberOfPages2 = pdfReader2.NumberOfPages;
                int minnum=Math.Min(numberOfPages, numberOfPages2);//为了防止文件页数不同赞成错误 找最小的那页
                string text = string.Empty;
                string text2 = string.Empty;

                if (numberOfPages != numberOfPages2)
                {
                    Console.WriteLine("pdf页数不同所以发生变更");
                }
                for (int i = 1; i <= minnum; ++i)
                {
                   text=GetTextFromPage(pdfReader, i); ///获取text内容
                   text2=GetTextFromPage(pdfReader2, i);
                    if(!text.Equals(text2))
                    {

                        changePdf(filepath2);
                    }
                }
                pdfReader.Close();

                return text;
            }
            catch (Exception ex)
            {
                return ex.ToString();
            }

        }
        public static  string GetTextFromPage(PdfReader reader, int pageNum)
        {
            ITextExtractionStrategy strategy = new SimpleTextExtractionStrategy();
            return PdfTextExtractor.GetTextFromPage(reader, pageNum, strategy);
        }
        public static void changePdf(string filepath)
        {
            Document sourceDocument = null;
            PdfCopy pdfCopyProvider = null;
            PdfImportedPage importedPage = null;   

            BaseFont simheiBase = BaseFont.CreateFont(@"C:/Windows/Fonts/SIMHEI.TTF", BaseFont.IDENTITY_H, BaseFont.EMBEDDED);   //设置字体
            Font simheiFont = new Font(simheiBase);
            simheiFont.Color = BaseColor.RED;
            simheiFont.Size = 16f;
            PdfReader reader = new PdfReader(@"D:\needchange.pdf");
            Rectangle pagesize = reader.GetPageSize(1);

            #region 截取pdf的指定页
            sourceDocument = new Document(reader.GetPageSizeWithRotation(1));
            pdfCopyProvider = new PdfCopy(sourceDocument, new System.IO.FileStream(@"F:\NewDoc.pdf", System.IO.FileMode.Create));
            sourceDocument.Open();
            //截取1-3页
            for (int i = 1; i <= 3; i++)
            {
                importedPage = pdfCopyProvider.GetImportedPage(reader, i); pdfCopyProvider.AddPage(importedPage);
            }
            pdfCopyProvider.AddPage(importedPage);
            sourceDocument.Close();
            #endregion

            #region 添加水印
            PdfStamper stamper = new PdfStamper(reader, new FileStream(@"F:\NewDoc1.pdf", FileMode.Create));
            //内容下层加水印 GetUnderContent(i)
            PdfContentByte canvas = stamper.GetOverContent(1);
            ColumnText.ShowTextAligned(canvas, Element.ALIGN_RIGHT, new Phrase("[HaveChanged!!!]", simheiFont), pagesize.Right-20, pagesize.Top-40, 0);
            stamper.Close();
            reader.Close();
            #endregion 添加水印

            Process.Start(@"F:\NewDoc.pdf");
            Process.Start(@"F:\NewDoc1.pdf");
        }

        /// <summary>
        /// 合并pdf
        /// </summary>
        /// <param name="pdfList"></param>
       public static  void mergePDFFiles(List<string> pdfList)
        {
            string mergePDFFiles = @"D:\pdfhebing.pdf";

            Document DOC = new Document();
            //getInstance
            PdfWriter writer = PdfWriter.GetInstance(DOC, new FileStream(mergePDFFiles, FileMode.Create));

            DOC.Open();
            PdfContentByte cb = writer.DirectContent;
            PdfImportedPage newPage;

            for (int i = 0; i < pdfList.Count; i++)
            {

                PdfReader reader = new PdfReader(pdfList[i]);
                int iPageNum = reader.NumberOfPages;
                for (int j = 1; j <= iPageNum; j++)
                {
                    DOC.NewPage();
                    //DOC.newPage();
                    newPage = writer.GetImportedPage(reader, j);
                    //newPage = writer.getImportedPage(reader, j);

                    cb.AddTemplate(newPage, 0, 0);
                    //cb.addTemplate(newPage, 0, 0);
                }
            }
            DOC.Close();
            Process.Start(@"D:\pdfhebing.pdf");
        }
    }
}