Creating a virtual printer to handle custom print job events

Question

I'm looking to create a .NET virtual printer that I can install on client's machines and have them print to it so that I can do some custom print job events such as:

• Parse the printjob for specific keywords and save the print out as PDF to specific folders depending on the keyword
• OCR the printjob if needed to detect the keywords

Anyone know of a library or software that can help me achieve this functionality?

Answer 1

There’s a customizable printer driver in the LEADTOOLS Virtual Printer SDK. (Disclosure: I work for LEADTOOLS vendor).

This forum post contains a C# demo project that uses the printer driver events to intercept print jobs and save them as PDF.

To parse the printed page text, I modified that project’s EMF event, which is triggered for every page in the print job, and obtained plain text from the page using the following code:

// Printed pages event
private static void Printer_EmfEvent(object sender, EmfEventArgs e)
{
   DocumentWriter tempDocWriter = new DocumentWriter();
   MemoryStream memoryStream = new MemoryStream();
   tempDocWriter.BeginDocument(memoryStream, DocumentFormat.Text);
   using (Metafile metaFile = new Metafile(e.Stream))
      tempDocWriter.AddPage(new DocumentWriterEmfPage()
      {
         EmfHandle = metaFile.GetHenhmetafile()
      });
   tempDocWriter.EndDocument(); // Save the page as TEXT format into the stream
   memoryStream.Position = 0;
   StreamReader streamReader = new StreamReader(memoryStream);
   string pageText = streamReader.ReadToEnd();
   //Now the string can be parsed
}

Regarding OCR, the toolkit also contains an OCR engine that can be used to convert image-based print jobs to text.

If you would like to try the SDK, there’s a free evaluation edition on this page.