Simple .NET PDF Merger

• Download source code - 1.1 MB

Introduction

There are a couple of PDF mergers available on the Internet. But, either they are commercial products or don't support printing of the header and/or footer text, which is particularly interesting, e.g., to print the page number.

Background

The presented PDF merger uses the open source PDF library iTextSharp to process PDF files. The sample solution also includes a tiny Windows Forms application to demonstrate the functionality.

Using the code

For the merge process, the PDF library takes advantage of the PDF page events of the iTextSharp.text.pdf.PdfWriter object. During the initialization of the PdfPageEvent instance (which inherits from iTextSharp.text.pdf.IPdfPageEvent), necessary information for the header/footer text could be passed in to the constructor call:

writer.PageEvent = new PdfPageEvents(/*Any type of information goes here*/);

It is important that the header and the footer text, both, are rendered in the 'public void OnEndPage(PdfWriter writer, Document document)' method. The 'public void OnStartPage(PdfWriter writer, Document document)' is not accurate.

Even though the shown sample is very basic, it generally gives a good overview of how the header and the footer can be populated, e.g., with picture(s), text(s)...

The source code

using System;
using System.Collections.Generic;
using System.IO;
using iTextSharp.text;
using iTextSharp.text.pdf;

namespace SmartSoft.PdfLibrary
{
    public static class PdfMerger
    {
        /// <summary>
        /// Merge pdf files.
        /// </summary>
        /// <param name="sourceFiles">PDF files being merged.</param>
        /// <returns></returns>
        public static byte[] MergeFiles(List<byte[]> sourceFiles)
        {
            Document document = new Document();
            MemoryStream output = new MemoryStream();

            try
            {
                // Initialize pdf writer
                PdfWriter writer = PdfWriter.GetInstance(document, output);
                writer.PageEvent = new PdfPageEvents();
                
                // Open document to write
                document.Open();
                PdfContentByte content = writer.DirectContent;

                // Iterate through all pdf documents
                for (int fileCounter = 0; fileCounter < sourceFiles.Count; fileCounter++)
                {
                    // Create pdf reader
                    PdfReader reader = new PdfReader(sourceFiles[fileCounter]);
                    int numberOfPages = reader.NumberOfPages;

                    // Iterate through all pages
                    for (int currentPageIndex = 1; currentPageIndex <= 
                                       numberOfPages; currentPageIndex++)
                    {
                        // Determine page size for the current page
                        document.SetPageSize(
                           reader.GetPageSizeWithRotation(currentPageIndex));
                        
                        // Create page
                        document.NewPage();
                        PdfImportedPage importedPage = 
                          writer.GetImportedPage(reader, currentPageIndex);

                        
                        // Determine page orientation
                        int pageOrientation = reader.GetPageRotation(currentPageIndex);
                        if ((pageOrientation == 90) || (pageOrientation == 270))
                        {
                            content.AddTemplate(importedPage, 0, -1f, 1f, 0, 0,
                               reader.GetPageSizeWithRotation(currentPageIndex).Height);
                        }
                        else
                        {
                            content.AddTemplate(importedPage, 1f, 0, 0, 1f, 0, 0);
                        }
                    }
                }
            }
            catch (Exception exception)
            {
                throw new Exception("There has an unexpected exception" + 
                      " occured during the pdf merging process.", exception);
            }
            finally
            {
                document.Close();
            }
            return output.GetBuffer();
        }
    }



    /// <summary>
    /// Implements custom page events.
    /// </summary>
    internal class PdfPageEvents : IPdfPageEvent
    {
        #region members
        private BaseFont _baseFont = null;
        private PdfContentByte _content;
        #endregion

        #region IPdfPageEvent Members
        public void OnOpenDocument(PdfWriter writer, Document document)
        {
            _baseFont = BaseFont.CreateFont(BaseFont.HELVETICA, 
                             BaseFont.CP1252, BaseFont.NOT_EMBEDDED);
            _content = writer.DirectContent;
        }

        public void OnStartPage(PdfWriter writer, Document document)
        {}

        public void OnEndPage(PdfWriter writer, Document document)
        {
            // Write header text
            string headerText = "PDF Merger by Smart-Soft";
            _content.BeginText();
            _content.SetFontAndSize(_baseFont, 8);
            _content.SetTextMatrix(GetCenterTextPosition(headerText, 
                                   writer), writer.PageSize.Height - 10);
            _content.ShowText(headerText);
            _content.EndText();

            // Write footer text (page numbers)
            string text = "Page " + writer.PageNumber;
            _content.BeginText();
            _content.SetFontAndSize(_baseFont, 8);
            _content.SetTextMatrix(GetCenterTextPosition(text, writer), 10);
            _content.ShowText(text);
            _content.EndText();
        }

        public void OnCloseDocument(PdfWriter writer, Document document)
        {}

        public void OnParagraph(PdfWriter writer, 
                    Document document, float paragraphPosition)
        {}

        public void OnParagraphEnd(PdfWriter writer, 
                    Document document, float paragraphPosition)
        {}

        public void OnChapter(PdfWriter writer, Document document, 
                              float paragraphPosition, Paragraph title)
        {}

        public void OnChapterEnd(PdfWriter writer, 
                    Document document, float paragraphPosition)
        {}

        public void OnSection(PdfWriter writer, Document document, 
                    float paragraphPosition, int depth, Paragraph title)
        {}

        public void OnSectionEnd(PdfWriter writer, 
                    Document document, float paragraphPosition)
        {}

        public void OnGenericTag(PdfWriter writer, Document document, 
                                 Rectangle rect, string text)
        {}
        #endregion

        private float GetCenterTextPosition(string text, PdfWriter writer)
        {
            return writer.PageSize.Width / 2 - _baseFont.GetWidthPoint(text, 8) / 2;
        }
    }
}

History

• 01.08.2008 - Article created.