While building the perfect apps with Apitron PDF Rasterizer for .NET you were probably thinking about own PDF text search functionality implementation.
It could be useful for custom viewers, and having this feature makes your PDF rendering toolkit really complete: you’d have the Apitron PDFRasterizer for rendering, Apitron PDF Viewer (our free pdf viewer control) for viewing and integrated text search for fast and efficient text search and navigation.
We did it for you.
From now on, the Apitron PDF Rasterizer has the integrated text search engine and you can easily use it in your apps.
The code
For demonstration purposes we will review a sample that opens PDF file, searches for some text, renders corresponding PDF page and highlights the results(complete C# code can be found under samples\SearchAndHighlightSpecifiedText folder in our download package).
Our PDF text search engine uses concept called search index, prior to searching we analyze the document and build its “index” - data used for actual searching. It can be stored by you for later use if you wish, so you could avoid its recreation next time the document is being opened.
Index creation
FileStream pdfDocumentStreamToSearch = newFileStream( Path.Combine( pathToDocuments, "2003_ar.pdf" ), FileMode.Open, FileAccess.Read );
SearchIndex searchIndex = newSearchIndex( pdfDocumentStreamToSearch );
As you see, index creation takes just a few lines of code. It’s also possible to save the index to output stream for later use. Password-protected PDF files are also supported.
Text search
I used the PDF document from Adobe website, http://www.adobe.com/aboutadobe/invrelations/pdfs/2003_ar.pdfand all images attached to this post represent actual output from the code sample.
staticvoid Main(string[] args)
{
string pathToDocument = @"..\Documents\2003_ar.pdf";
// create index from PDF file
using ( StreampdfDocumentStreamToSearch = newFileStream( pathToDocument, FileMode.Open, FileAccess.Read ) )
{
SearchIndex searchIndex = newSearchIndex(pdfDocumentStreamToSearch);
// create document used for rendering
using ( StreampdfDocumentStreamToRasterize = newFileStream( pathToDocument, FileMode.Open, FileAccess.Read ) )
{
document = newDocument(pdfDocumentStreamToRasterize);
// search text in PDF document and render pages containing results
searchIndex.Search( SearchHandler, "software products derive" );
}
}
}
///<summary>
/// Handle search results here. Draw pages with highlighted text.
///</summary>
///<param name="handlerArgs">The handler args.</param>
privatestaticvoid SearchHandler(SearchHandlerArgshandlerArgs)
{
if (handlerArgs.ResultItems.Count != 0)
{
string outputFileName = string.Format("{0}.png", handlerArgs.PageIndex);
Page page = document.Pages[handlerArgs.PageIndex];
using (Imagebm = page.Render((int)page.Width * 2, (int)page.Height * 2, renderingSettings))
{
foreach (SearchResultItemsearchResultItem in handlerArgs.ResultItems)
{
HighlightSearchResult(bm, searchResultItem, page);
}
bm.Save( outputFileName );
}
Process.Start( outputFileName );
}
// Search cancellation condition, now we stop if we have more than 3 results found,
// or all pages are searched
if (handlerArgs.ResultItems.Count > 3)
{
handlerArgs.CancelSearch = true;
}
}
What happens here? We take the previously created index data and call the SearchIndex.Search method accepting the search event handler.
Resulting images
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| Resulting image(see yellow markers) |
 |
| One of the results produced by searching for “Intelligent Documents” |
 |
| Result produced for spiral text |
How to get it
The described PDF search engine is included in latest Apitron PDF Rasterizer for .NET release, all related classes can be found under Apitron.PDF.Rasterizer.Search namespace. We always welcome any feedback, so feel free to ask questions and share ideas.