Philip Hendry's Blog

Create a contents page with page numbers from html input using Websupergoo Abcpdf

Dec 23, 2011 • ASP.NET • 2 min read

I’ve created a report pdf from an html page output from our ASP.NET based product but I needed to change a contents list that was rendered as a hyperlink list on the page into a list of section headings and page number since the pdf was primarily for printing. The solution wasn’t immediately obvious but I’ve come up with the following which I was running in a unit test for simple quick prototyping. The key is using the HtmlOptions.AddTags property in ABCpdf which allows areas of the HTML to be retrieve during pdf rendering and modified.

using System.Diagnostics;
using System.IO;
using System.Collections.Generic;
using System.Linq;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using WebSupergoo.ABCpdf8;

namespace TestPdfFormFields
    public class PdfPrototyping
        struct Tag
            public string name;
            public string rectString;
            public int pagenumber;

        public void testCreatingAPdfWithContentsPageFromHtml()
            // Create Websupergoo ABCpdf document and set up the page size
            var theDoc = new Doc();
            theDoc.Rect.Inset(100, 100);
            theDoc.Rect.Top = 700;

            // The following HtmlOption instructs ABCpdf to interpret the style tags 'abcpdf-tag-visible' and
            // create a array of the id's take from the html and the rectangles representing the size of the
            // html element.
            theDoc.HtmlOptions.AddTags = true;

            // The basis of this solution therefore is to create placeholders where page numbers will be rendered
            // in the contents page and back-fill them once we know where the sections/chapters have been rendered
            // since it won't be known until ABCpdf has chained pages together.
            var theID = theDoc.AddImageHtml(
                    <li><span id='contents1' style='abcpdf-tag-visible: true; width: 20px;'></span>.......First paragraph</li>
                    <li><span id='contents2' style='abcpdf-tag-visible: true; width: 20px;'></span>.......Second paragraph</li>
                    <li><span id='contents3' style='abcpdf-tag-visible: true; width: 20px;'></span>.......Third paragraph</li>
                <h1 id='heading1' style='abcpdf-tag-visible: true; page-break-before:always;'>Section One</h1>
                <h1 id='heading2' style='abcpdf-tag-visible: true; page-break-before:always;'>Section Two</h1>
                <h1 id='heading3' style='abcpdf-tag-visible: true; page-break-before:always;'>Section Three</h1>

            var tagCache = new List<Tag>();
            var pagenumber = 1;
            while (true)
                // Fetch all the tags and rectangles and add them to a tagCache for the current theID. Chaining
                // creates a new theID which will contain more tags to add
                var tags = theDoc.HtmlOptions.GetTagIDs(theID);
                var tagRects = theDoc.HtmlOptions.GetTagRects(theID);
                tagCache.AddRange(tags.Select((t, i) => new Tag {name = t, pagenumber = pagenumber, rectString = tagRects[i].String}));

                if (!theDoc.Chainable(theID))

                theDoc.Page = theDoc.AddPage();
                theID = theDoc.AddImageToChain(theID);

            // Now we have a cache of all contents and heading tags we can iterate through the
            // contents tags, find the smallest page number of the corresponding section then
            // render the page number into the contents.
            theDoc.HPos = 1.0; // Right justify
            theDoc.VPos = 0.5; // Centre vertically
            theDoc.FontSize = 8;
            foreach (var tag in tagCache.Where(t =>"contents")))
                var paragraphName = "heading" +"contents".Length);
                var paragraphPageNumber = tagCache.Where(t => == paragraphName).Select(t => t.pagenumber).Min();

                theDoc.PageNumber = tag.pagenumber;
                theDoc.Rect.String = tag.rectString;

            // Now iterate through all the pages, add page numbers and flatten the layers.
            theDoc.Rect.String = "100 70 500 150";
            var pageCount = theDoc.PageCount;
            for (var pageNumber = 1; pageNumber <= pageCount; pageNumber++)
                theDoc.PageNumber = pageNumber;
                theDoc.AddText("Page " + pageNumber + " of " + pageCount);

            const string testFilename = @"c:\temp\HtmlOptionsGetTagRects.pdf";
            if (File.Exists(testFilename))

Post by: Philip Hendry