Public Sub AppendLtd( _
   ByVal sourceFileName As String, _
   ByVal destFileName As String _
) 

Dim instance As DocumentWriter
Dim sourceFileName As String
Dim destFileName As String
 
instance.AppendLtd(sourceFileName, destFileName)

public void AppendLtd( 
   string sourceFileName,
   string destFileName
)

public:
void AppendLtd( 
   String^ sourceFileName,
   String^ destFileName
) 

Public Shared Sub AppendLtdExample()
      ' Unlock the support needed for LEADTOOLS Document Writers (with PDF output)
      RasterSupport.Unlock(RasterSupportType.Document, "Replace with your own key here")
      RasterSupport.Unlock(RasterSupportType.OcrProfessional, "Replace with your own key here")
      RasterSupport.Unlock(RasterSupportType.OcrProfessionalPdfLeadOutput, "Replace with your own key here")
      ' Get a multi-page source file
      Dim sourceFileName As String = GetImageFileName()
      Dim destFileName As String = Path.Combine(LEAD_VARS.ImagesDir, "AppendLtdExample.pdf")
      File.Delete(destFileName)

      ' Use OCR Professional engine
      Using ocrEngine As IOcrEngine = OcrEngineManager.CreateEngine(OcrEngineType.Professional, False)
         ocrEngine.Startup(Nothing, Nothing, Nothing, Nothing)

         ' Get the number of pages in the source file
         Dim pageCount As Integer
         Using imageInfo As CodecsImageInfo = ocrEngine.RasterCodecsInstance.GetInformation(sourceFileName, True)
            pageCount = imageInfo.TotalPages
         End Using

         Console.WriteLine("OCRing {0} pages", pageCount)

         ' Use all possible cores
         Dim maxThreads As Integer = Environment.ProcessorCount
         Console.WriteLine("Machine has {0} cores", maxThreads)

         Dim threadCount As Integer = Math.Min(maxThreads, pageCount)
         Console.WriteLine("Using {0} threads", threadCount)

         ' Initialie the thread parameters
         Dim threadParams(threadCount - 1) As MyThreadParam
         For i As Integer = 0 To threadCount - 1
            threadParams(i) = New MyThreadParam()
            threadParams(i).ThreadFinishedEvent = New AutoResetEvent(False)
            threadParams(i).OcrEngine = ocrEngine
            ' We can re-use the documents, so create them once here
            threadParams(i).OcrDocument = ocrEngine.DocumentManager.CreateDocument()
            threadParams(i).SourceFileName = sourceFileName
            ' We can re-use the LTD files, so get them here once
            threadParams(i).LtdFileName = Path.GetTempFileName()
         Next

         ' This is the LTD file we will use to append all recognition data
         ' from all threads
         Dim mainLtdFileName As String = Path.GetTempFileName()
         File.Delete(mainLtdFileName)

         Dim pageNumber As Integer = 1
         While pageNumber <= pageCount
            Dim queuedUpEvents As New List(Of AutoResetEvent)

            ' Queue up the threads, each thread will have its own
            ' IOcrDocument to recognize one page to a separate LTD file
            Dim ltdCounter As Integer = 0
            For threadIndex As Integer = 0 To threadCount - 1
               If pageNumber <= pageCount Then
                  ' Queue up this page
                  Console.WriteLine("Queing up page {0}", pageNumber)
                  threadParams(threadIndex).PageNumber = pageNumber
                  queuedUpEvents.Add(threadParams(threadIndex).ThreadFinishedEvent)
                  ThreadPool.QueueUserWorkItem(AddressOf MyThreadProc, threadParams(threadIndex))
                  pageNumber = pageNumber + 1
                  ltdCounter = ltdCounter + 1
               End If
            Next

            ' Wait for the queued up threads to finish
            Console.WriteLine("Waiting on queued up pages to finished")
            WaitHandle.WaitAll(queuedUpEvents.ToArray())

            Console.WriteLine("Appending LTDs")
            For i As Integer = 0 To ltdCounter - 1
               ' Notice, first time, the main LTD does not exist, AppendLtd will
               ' just copy the data over from the source file
               ocrEngine.DocumentWriterInstance.AppendLtd(threadParams(i).LtdFileName, mainLtdFileName)
            Next
         End While

         ' We are done, convert the LTD to final format, here, we will
         ' use PDF
         Console.WriteLine("Converting to final format")
         ocrEngine.DocumentWriterInstance.Convert(mainLtdFileName, destFileName, DocumentFormat.Pdf)

         ' Clean-up
         For i As Integer = 0 To threadCount - 1
            threadParams(i).ThreadFinishedEvent.Close()
            threadParams(i).OcrDocument.Dispose()
         Next

         Console.WriteLine("Success, file {0} is created", destFileName)
      End Using
   End Sub

   Class MyThreadParam
      ' Event to trigger when recognition is done
      Public ThreadFinishedEvent As AutoResetEvent
      ' OCR engine to use
      Public OcrEngine As IOcrEngine
      ' OCR Document to use
      Public OcrDocument As IOcrDocument
      ' Source image file
      Public SourceFileName As String
      ' Page number to recognize by this thread
      Public PageNumber As Integer
      ' LTD file to save temporary recognition data
      Public LtdFileName As String
   End Class

   Private Shared Sub MyThreadProc(ByVal state As Object)
      Dim threadParams As MyThreadParam = CType(state, MyThreadParam)
      Console.WriteLine("  Thread {0} is working on pages {1}", Thread.CurrentThread.GetHashCode(), threadParams.PageNumber)

      Try
         ' Delete the LTD file if it exists so we can put fresh data in it
         File.Delete(threadParams.LtdFileName)

         ' Clear any previous pages in this document
         threadParams.OcrDocument.Pages.Clear()

         ' Load the page
         Console.WriteLine("  Thread {0} is loading the page", Thread.CurrentThread.GetHashCode())
         threadParams.OcrDocument.Pages.AddPages(threadParams.SourceFileName, threadParams.PageNumber, threadParams.PageNumber, Nothing)

         ' Get it, it is the last page we added
         Dim ocrPage As IOcrPage = threadParams.OcrDocument.Pages(threadParams.OcrDocument.Pages.Count - 1)

         ' Auto-zone it
         Console.WriteLine("  Thread {0} is auto-zoning the page", Thread.CurrentThread.GetHashCode())
         ocrPage.AutoZone(Nothing)

         ' Recognize it
         Console.WriteLine("  Thread {0} is recognizing the page", Thread.CurrentThread.GetHashCode())
         ocrPage.Recognize(Nothing)

         ' Save it
         Console.WriteLine("  Thread {0} is saving the page", Thread.CurrentThread.GetHashCode())
         threadParams.OcrDocument.Save(threadParams.LtdFileName, DocumentFormat.Ltd, Nothing)
      Finally
         Console.WriteLine("  Thread {0} is done", Thread.CurrentThread.GetHashCode())
         threadParams.ThreadFinishedEvent.Set()
      End Try
   End Sub

   Private Shared Function GetImageFileName() As String
      Dim pageTileTemplate As String = Path.Combine(LEAD_VARS.ImagesDir, "Ocr{0}.tif")
      Dim multiPageImageFileName As String = Path.Combine(LEAD_VARS.ImagesDir, "AppendLtdExample.tif")

      File.Delete(multiPageImageFileName)

      ' Create a multi-page TIF file by stitching OCR1 to OCR4.tif shipped with LEADTOOLS
      Using codecs As New RasterCodecs()
         Dim finalImage As RasterImage = Nothing

         For page As Integer = 1 To 4
            Dim pageImage As RasterImage = codecs.Load(String.Format(pageTileTemplate, page))
            If IsNothing(finalImage) Then
               finalImage = pageImage
            Else
               finalImage.AddPage(pageImage)
               pageImage.Dispose()
            End If
         Next

         ' Save the final image
         codecs.Save(finalImage, multiPageImageFileName, RasterImageFormat.CcittGroup4, 1)
      End Using

      Return multiPageImageFileName
   End Function

Public NotInheritable Class LEAD_VARS
   Public Const ImagesDir As String = "C:\Users\Public\Documents\LEADTOOLS Images"
End Class

public static void AppendLtdExample()
   {
      // Unlock the support needed for LEADTOOLS Document Writers (with PDF output)
      RasterSupport.Unlock(RasterSupportType.Document, "Replace with your own key here");
      RasterSupport.Unlock(RasterSupportType.OcrProfessional, "Replace with your own key here");
      RasterSupport.Unlock(RasterSupportType.OcrProfessionalPdfLeadOutput, "Replace with your own key here");
      // Get a multi-page source file
      string sourceFileName = GetImageFileName();
      string destFileName = Path.Combine(LEAD_VARS.ImagesDir,"AppendLtdExample.pdf");
      File.Delete(destFileName);

      // Use OCR Professional engine
      using(IOcrEngine ocrEngine = OcrEngineManager.CreateEngine(OcrEngineType.Professional, false))
      {
         ocrEngine.Startup(null, null, null, null);

         // Get the number of pages in the source file
         int pageCount;
         using(CodecsImageInfo imageInfo = ocrEngine.RasterCodecsInstance.GetInformation(sourceFileName, true))
         {
            pageCount = imageInfo.TotalPages;
         }

         Console.WriteLine("OCRing {0} pages", pageCount);

         // Use all possible cores
         int maxThreads = Environment.ProcessorCount;
         Console.WriteLine("Machine has {0} cores", maxThreads);

         int threadCount = Math.Min(maxThreads, pageCount);
         Console.WriteLine("Using {0} threads", threadCount);

         // Initialie the thread parameters
         MyThreadParam[] threadParams = new MyThreadParam[threadCount];
         for(int i = 0; i < threadCount; i++)
         {
            threadParams[i] = new MyThreadParam();
            threadParams[i].ThreadFinishedEvent = new AutoResetEvent(false);
            threadParams[i].OcrEngine = ocrEngine;
            // We can re-use the documents, so create them once here
            threadParams[i].OcrDocument = ocrEngine.DocumentManager.CreateDocument();
            threadParams[i].SourceFileName = sourceFileName;
            // We can re-use the LTD files, so get them here once
            threadParams[i].LtdFileName = Path.GetTempFileName();
         }

         // This is the LTD file we will use to append all recognition data
         // from all threads
         string mainLtdFileName = Path.GetTempFileName();
         File.Delete(mainLtdFileName);

         int pageNumber = 1;
         while(pageNumber <= pageCount)
         {
            List<AutoResetEvent> queuedUpEvents = new List<AutoResetEvent>();

            // Queue up the threads, each thread will have its own
            // IOcrDocument to recognize one page to a separate LTD file
            int ltdCounter = 0;
            for(int threadIndex = 0; threadIndex < threadCount; threadIndex++)
            {
               if(pageNumber <= pageCount)
               {
                  // Queue up this page
                  Console.WriteLine("Queing up page {0}", pageNumber);
                  threadParams[threadIndex].PageNumber = pageNumber;
                  queuedUpEvents.Add(threadParams[threadIndex].ThreadFinishedEvent);
                  ThreadPool.QueueUserWorkItem(new WaitCallback(MyThreadProc), threadParams[threadIndex]);
                  pageNumber++;
                  ltdCounter++;
               }
            }

            // Wait for the queued up threads to finish
            Console.WriteLine("Waiting on queued up pages to finished");
            WaitHandle.WaitAll(queuedUpEvents.ToArray());

            Console.WriteLine("Appending LTDs");
            for(int i = 0; i < ltdCounter; i++)
            {
               // Notice, first time, the main LTD does not exist, AppendLtd will
               // just copy the data over from the source file
               ocrEngine.DocumentWriterInstance.AppendLtd(threadParams[i].LtdFileName, mainLtdFileName);
            }
         }

         // We are done, convert the LTD to final format, here, we will
         // use PDF
         Console.WriteLine("Converting to final format");
         ocrEngine.DocumentWriterInstance.Convert(mainLtdFileName, destFileName, DocumentFormat.Pdf);

         // Clean-up
         for(int i = 0; i < threadCount; i++)
         {
            threadParams[i].ThreadFinishedEvent.Close();
            threadParams[i].OcrDocument.Dispose();
         }

         Console.WriteLine("Success, file {0} is created", destFileName);
      }
   }

   class MyThreadParam
   {
      // Event to trigger when recognition is done
      public AutoResetEvent ThreadFinishedEvent;
      // OCR engine to use
      public IOcrEngine OcrEngine;
      // OCR Document to use
      public IOcrDocument OcrDocument;
      // Source image file
      public string SourceFileName;
      // Page number to recognize by this thread
      public int PageNumber;
      // LTD file to save temporary recognition data
      public string LtdFileName;
   }

   private static void MyThreadProc(object state)
   {
      MyThreadParam threadParams = state as MyThreadParam;
      Console.WriteLine("  Thread {0} is working on pages {1}", Thread.CurrentThread.GetHashCode(), threadParams.PageNumber);

      try
      {
         // Delete the LTD file if it exists so we can put fresh data in it
         File.Delete(threadParams.LtdFileName);

         // Clear any previous pages in this document
         threadParams.OcrDocument.Pages.Clear();

         // Load the page
         Console.WriteLine("  Thread {0} is loading the page", Thread.CurrentThread.GetHashCode());
         threadParams.OcrDocument.Pages.AddPages(threadParams.SourceFileName, threadParams.PageNumber, threadParams.PageNumber, null);

         // Get it, it is the last page we added
         IOcrPage ocrPage = threadParams.OcrDocument.Pages[threadParams.OcrDocument.Pages.Count - 1];

         // Auto-zone it
         Console.WriteLine("  Thread {0} is auto-zoning the page", Thread.CurrentThread.GetHashCode());
         ocrPage.AutoZone(null);

         // Recognize it
         Console.WriteLine("  Thread {0} is recognizing the page", Thread.CurrentThread.GetHashCode());
         ocrPage.Recognize(null);

         // Save it
         Console.WriteLine("  Thread {0} is saving the page", Thread.CurrentThread.GetHashCode());
         threadParams.OcrDocument.Save(threadParams.LtdFileName, DocumentFormat.Ltd, null);
      }
      finally
      {
         Console.WriteLine("  Thread {0} is done", Thread.CurrentThread.GetHashCode());
         threadParams.ThreadFinishedEvent.Set();
      }
   }

   private static string GetImageFileName()
   {
      string pageTileTemplate = Path.Combine(LEAD_VARS.ImagesDir,"Ocr{0}.tif");
      string multiPageImageFileName = Path.Combine(LEAD_VARS.ImagesDir,"AppendLtdExample.tif");

      File.Delete(multiPageImageFileName);

      // Create a multi-page TIF file by stitching OCR1 to OCR4.tif shipped with LEADTOOLS
      using(RasterCodecs codecs = new RasterCodecs())
      {
         RasterImage finalImage = null;

         for(int page = 1; page <= 4; page++)
         {
            RasterImage pageImage = codecs.Load(string.Format(pageTileTemplate, page));
            if(finalImage == null)
            {
               finalImage = pageImage;
            }
            else
            {
               finalImage.AddPage(pageImage);
               pageImage.Dispose();
            }
         }

         // Save the final image
         codecs.Save(finalImage, multiPageImageFileName, RasterImageFormat.CcittGroup4, 1);
      }

      return multiPageImageFileName;
   }

static class LEAD_VARS
{
   public const string ImagesDir = @"C:\Users\Public\Documents\LEADTOOLS Images";
}