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    copied!<p>Hopefully this can help someone else.</p> <p>I ended up using both ABCPDF and iTextSharp.</p> <p>I used ABCPDF to convert the HTML to PDF, and to tell me where the element is, and then I used iTextSharp to put the blank signature field over it.</p> <p>There were a couple of "gotchas" in this project:</p> <ol> <li>ABCPDF was better at converting HTML to PDF because it is more forgiving with non-standard html, and it was better at reading the physical paths when they contained small mistakes like "/" instead of "\".</li> <li>When sending your html to the PDF converter (iTextSharp or ABCPDF), the relative paths need to be changed into physical paths because the converter won't know in which web-site you are running or in which virtual directories to find the images, scripts and stylesheets. (See a converter below that can help with that)</li> <li>ABCPDF was better at interpreting the style sheets, and the end result looked much better with less code.</li> <li>When trying to figure out where ABCPDF placed the fields or tagged elements, bear in mind that after you add the first page, you still have to go into a loop to "chain" or register the rest of the pages, then only will you be able to resolve the field or the tagged element.</li> </ol> <p>Here is a sample project to demonstrate the solution.</p> <p>The sample html: (notice the <strong>abcpdf-tag-visible: true</strong> part in the style of the signature field, this will help us to see where the element is placed in the PDF)</p> <pre><code>&lt;!DOCTYPE html&gt; &lt;html lang="en" xmlns="http://www.w3.org/1999/xhtml"&gt; &lt;head&gt; &lt;meta charset="utf-8" /&gt; &lt;title&gt;Test Document&lt;/title&gt; &lt;/head&gt; &lt;body&gt; &lt;form method="POST"&gt; Sample Report Data: &lt;br /&gt; &lt;table style="border: solid 1px red; margin: 5px" cellpadding="5px"&gt; &lt;tr&gt; &lt;td&gt;Field 1:&lt;/td&gt; &lt;td&gt;&lt;input type="text" id="field1" name="field1" value="FIELD1VALUE" /&gt;&lt;/td&gt; &lt;/tr&gt; &lt;tr&gt; &lt;td&gt;Field 2:&lt;/td&gt; &lt;td&gt;&lt;input type="text" id="Text2" value="FIELD2VALUE" /&gt;&lt;/td&gt; &lt;/tr&gt; &lt;tr&gt; &lt;td&gt;Field 3:&lt;/td&gt; &lt;td&gt;&lt;input type="text" id="Text3" value="FIELD3VALUE" /&gt;&lt;/td&gt; &lt;/tr&gt; &lt;tr&gt; &lt;td&gt;Field 4:&lt;/td&gt; &lt;td&gt;&lt;input type="text" id="Text4" value="FIELD4VALUE" /&gt;&lt;/td&gt; &lt;/tr&gt; &lt;tr&gt; &lt;td&gt;Signature:&lt;/td&gt; &lt;td&gt;&lt;textarea id="ClientSignature" style="background-color:LightCyan;border-color:Gray;border-width:1px;border-style:Solid;height:50px;width:200px;abcpdf-tag-visible: true" rows="2" cols="20"&gt;&lt;/textarea&gt;&lt;/td&gt; &lt;/tr&gt; &lt;/table&gt; &lt;/form&gt; &lt;/body&gt; &lt;/html&gt; </code></pre> <p>Here is a screen shot of the PDF with a blank signature field, opened with Adobe afterwards.</p> <p><img src="https://i.stack.imgur.com/x7PIF.jpg" alt="pdfresultscreenshot"></p> <p>A sample console application to help test out the PDF converters:</p> <pre><code>namespace ABCPDFHtmlSignatureTest { using System; using System.Diagnostics; using System.IO; using System.Reflection; using iTextSharp.text; using iTextSharp.text.pdf; using WebSupergoo.ABCpdf8; /// &lt;summary&gt; /// The program. /// &lt;/summary&gt; public class Program { /// &lt;summary&gt; /// The file name. /// &lt;/summary&gt; private const string PdfFileName = @"c:\temp\pdftest.pdf"; /// &lt;summary&gt; /// Adds a blank signature field at the specified location. /// &lt;/summary&gt; /// &lt;param name="pdf"&gt;The PDF.&lt;/param&gt; /// &lt;param name="signatureRect"&gt;The signature location.&lt;/param&gt; /// &lt;param name="signaturePage"&gt;the page on which the signature appears&lt;/param&gt; /// &lt;returns&gt;The new PDF.&lt;/returns&gt; private static byte[] AddBlankSignatureField(byte[] pdf, Rectangle signatureRect, int signaturePage) { var pdfReader = new PdfReader(pdf); using (var ms = new MemoryStream()) { var pdfStamper = new PdfStamper(pdfReader, ms); var signatureField = PdfFormField.CreateSignature(pdfStamper.Writer); signatureField.SetWidget(signatureRect, null); signatureField.Flags = PdfAnnotation.FLAGS_PRINT; signatureField.Put(PdfName.DA, new PdfString("/Helv 0 Tf 0 g")); signatureField.FieldName = "ClientSignature"; signatureField.Page = signaturePage; pdfStamper.AddAnnotation(signatureField, signaturePage); pdfStamper.Close(); return ms.ToArray(); } } /// &lt;summary&gt; /// The application entry point. /// &lt;/summary&gt; /// &lt;param name="args"&gt; /// The args. /// &lt;/param&gt; public static void Main(string[] args) { var html = GetHtml(); XRect signatureRect; int signaturePage; byte[] pdf; GetPdfUsingAbc(html, out pdf, out signatureRect, out signaturePage); /* convert to type that iTextSharp needs */ var signatureRect2 = new Rectangle( Convert.ToSingle(signatureRect.Left), Convert.ToSingle(signatureRect.Top), Convert.ToSingle(signatureRect.Right), Convert.ToSingle(signatureRect.Bottom)); pdf = AddBlankSignatureField(pdf, signatureRect2, signaturePage); /* save the PDF to disk */ File.WriteAllBytes(PdfFileName, pdf); /* open the PDF */ Process.Start(PdfFileName); } /// &lt;summary&gt; /// Returns the PDF for the specified html. The conversion is done using ABCPDF. /// &lt;/summary&gt; /// &lt;param name="html"&gt;The html.&lt;/param&gt; /// &lt;param name="pdf"&gt;the PDF&lt;/param&gt; /// &lt;param name="signatureRect"&gt;the location of the signature field&lt;/param&gt; /// &lt;param name="signaturePage"&gt;the page of the signature field&lt;/param&gt; public static void GetPdfUsingAbc(string html, out byte[] pdf, out XRect signatureRect, out int signaturePage) { var document = new Doc(); document.MediaBox.String = "A4"; document.Color.String = "255 255 255"; document.FontSize = 7; /* tag elements marked with "abcpdf-tag-visible: true" */ document.HtmlOptions.AddTags = true; int pageId = document.AddImageHtml(html, true, 950, true); int pageNumber = 1; signatureRect = null; signaturePage = -1; TryIdentifySignatureLocationOnCurrentPage(document, pageId, pageNumber, ref signatureRect, ref signaturePage); while (document.Chainable(pageId)) { document.Page = document.AddPage(); pageId = document.AddImageToChain(pageId); pageNumber++; TryIdentifySignatureLocationOnCurrentPage(document, pageId, pageNumber, ref signatureRect, ref signaturePage); } pdf = document.GetData(); } /// &lt;summary&gt; /// The try identify signature location on current page. /// &lt;/summary&gt; /// &lt;param name="document"&gt;The document.&lt;/param&gt; /// &lt;param name="currentPageId"&gt;The current page id.&lt;/param&gt; /// &lt;param name="currentPageNumber"&gt;The current page number.&lt;/param&gt; /// &lt;param name="signatureRect"&gt;The signature location.&lt;/param&gt; /// &lt;param name="signaturePage"&gt;The signature page.&lt;/param&gt; private static void TryIdentifySignatureLocationOnCurrentPage(Doc document, int currentPageId, int currentPageNumber, ref XRect signatureRect, ref int signaturePage) { if (null != signatureRect) return; var tagIds = document.HtmlOptions.GetTagIDs(currentPageId); if (tagIds.Length &gt; 0) { int index = -1; foreach (var tagId in tagIds) { index++; if (tagId.Contains("ClientSignature")) { var rects = document.HtmlOptions.GetTagRects(currentPageId); signatureRect = rects[index]; signaturePage = currentPageNumber; break; } } } } /// &lt;summary&gt; /// The get html. /// &lt;/summary&gt; /// &lt;returns&gt; /// The &lt;see cref="string"/&gt;. /// &lt;/returns&gt; public static string GetHtml() { using (var stream = Assembly.GetExecutingAssembly().GetManifestResourceStream("ABCPDFHtmlSignatureTest.HTMLPage1.html")) { if (null == stream) { throw new InvalidOperationException("Unable to resolve the html"); } using (var streamReader = new StreamReader(stream)) { return streamReader.ReadToEnd(); } } } } } </code></pre> <p>When running inside the web server and still generating the HTML, you can use this class to change the relative (virtual) paths to physical (UNC) paths:</p> <pre><code>namespace YourNameSpace { using System; using System.Collections.Generic; using System.IO; using System.Text; using System.Web; /// &lt;summary&gt; /// Replaces all uris within in an html document to physical paths, making it valid /// html outside the context of a web site. This is necessary because outside the /// context of a web site root folder, the uris are meaningless, and the html cannot /// be interpreted correctly by external components, like ABCPDF or iTextSharp. /// Without this step, the images and other 'SRC' references cannot be resolved. /// &lt;/summary&gt; public sealed class HtmlRelativeToPhysicalPathConverter { #region FIELDS /// &lt;summary&gt; /// The _server. /// &lt;/summary&gt; private readonly HttpServerUtility _server; /// &lt;summary&gt; /// The _html. /// &lt;/summary&gt; private readonly string _html; #endregion #region CONSTRUCTOR /// &lt;summary&gt; /// Initialises a new instance of the &lt;see cref="HtmlRelativeToPhysicalPathConverter"/&gt; class. /// &lt;/summary&gt; /// &lt;param name="server"&gt; /// The server. /// &lt;/param&gt; /// &lt;param name="html"&gt; /// The html. /// &lt;/param&gt; /// &lt;exception cref="ArgumentNullException"&gt; /// when &lt;paramref name="server"/&gt; or &lt;paramref name="html"/&gt; is null or empty. /// &lt;/exception&gt; public HtmlRelativeToPhysicalPathConverter(HttpServerUtility server, string html) { if (null == server) throw new ArgumentNullException("server"); if (string.IsNullOrWhiteSpace(html)) throw new ArgumentNullException("html"); _server = server; _html = html; } #endregion #region Convert Html /// &lt;summary&gt; /// Convert the html. /// &lt;/summary&gt; /// &lt;param name="leaveUrisIfFileCannotBeFound"&gt;an additional validation can be performed before changing the uri to a directory path&lt;/param&gt; /// &lt;returns&gt;The converted html with physical paths in all uris.&lt;/returns&gt; public string ConvertHtml(bool leaveUrisIfFileCannotBeFound = false) { var htmlBuilder = new StringBuilder(_html); // Double quotes foreach (var relativePath in this.GetRelativePaths(htmlBuilder, '"')) { this.ReplaceRelativePath(htmlBuilder, relativePath, leaveUrisIfFileCannotBeFound); } // Single quotes foreach (var relativePath in this.GetRelativePaths(htmlBuilder, '\'')) { this.ReplaceRelativePath(htmlBuilder, relativePath, leaveUrisIfFileCannotBeFound); } return htmlBuilder.ToString(); } #endregion #region Replace Relative Path /// &lt;summary&gt; /// Convert a uri to the physical path. /// &lt;/summary&gt; /// &lt;param name="htmlBuilder"&gt;The html builder.&lt;/param&gt; /// &lt;param name="relativePath"&gt;The relative path or uri string.&lt;/param&gt; /// &lt;param name="leaveUrisIfFileCannotBeFound"&gt;an additional validation can be performed before changing the uri to a directory path&lt;/param&gt; private void ReplaceRelativePath(StringBuilder htmlBuilder, string relativePath, bool leaveUrisIfFileCannotBeFound) { try { var parts = relativePath.Split('?'); var mappedPath = _server.MapPath(parts[0]); if ((leaveUrisIfFileCannotBeFound &amp;&amp; File.Exists(mappedPath)) || !leaveUrisIfFileCannotBeFound) { if (parts.Length &gt; 1) { mappedPath += "?" + parts[1]; } htmlBuilder.Replace(relativePath, mappedPath); } else { /* decide what you want to do with these */ } } catch (ArgumentException) { /* ignore these */ } } #endregion #region Get Relative Paths /// &lt;summary&gt; /// They are NOT guaranteed to be valid uris, simply values between quote characters. /// &lt;/summary&gt; /// &lt;param name="html"&gt;the html builder&lt;/param&gt; /// &lt;param name="quoteChar"&gt;the quote character to use, e.g. " or '&lt;/param&gt; /// &lt;returns&gt;each of the relative paths&lt;/returns&gt; private IEnumerable&lt;string&gt; GetRelativePaths(StringBuilder html, char quoteChar) { var position = 0; var oldPosition = -1; var htmlString = html.ToString(); var previousUriString = string.Empty; while (oldPosition != position) { oldPosition = position; position = htmlString.IndexOf(quoteChar, position + 1); if (position == -1) break; var uriString = htmlString.Substring(oldPosition + 1, (position - oldPosition) - 1); if (Uri.IsWellFormedUriString(uriString, UriKind.Relative) &amp;&amp; uriString != previousUriString /* as far as I know we never reference a file without an extension, so avoid the IDs this way */ &amp;&amp; uriString.Contains(".") &amp;&amp; !uriString.EndsWith(".")) { yield return uriString; /* refresh the html string, and reiterate again */ htmlString = html.ToString(); position = oldPosition; oldPosition = position - 1; /* don't exit yet */ previousUriString = uriString; } } } #endregion } } </code></pre> <p>You can use the class like this:</p> <pre><code>var html = textWriter.ToString(); // change relative paths to be absolute html = new HtmlRelativeToPhysicalPathConverter(server, html).ConvertHtml(); </code></pre>
 

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