AppendLtd Method

Appends one LEADTOOLS Temporary Document (LTD) file to another.

Syntax

public void AppendLtd( 
   string sourceFileName,
   string destFileName
)

public void AppendLtd( 
   string sourceFileName,
   string destFileName
)

- (BOOL)appendLtdFile:(NSString *)srcLtdFile 
   destinationLtdFile:(NSString *)dstLtdFile 
                error:(NSError **)error

public void appendLtd(String sourceFileName, String destFileName)

 function Leadtools.Forms.DocumentWriters.DocumentWriter.AppendLtd( 
   sourceFileName ,
   destFileName 
)

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

'Declaration

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

'Usage

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

Parameters

sourceFileName: The source LTD file.
destFileName: The destination LTD file.

Remarks

You can use this method to append several LTD files together before calling Convert. The example below shows how this can be useful in a multi-threading OCR solution.

sourceFileName must exist on disk before calling this method, otherwise, an exception will be thrown.

destFileName may or may not exit prior to calling this method, if it does not exist, a new file is created and the data is copied as is from the source file.

When this method returns, destFileName will contain all the pages from the source and destination file (if exists), for example if the source file has 10 pages and the destination file has 20 pages, the result will be an LTD with 30 pages in destFileName with the 10 pages from the source file appended to the end of the destination file at page index 20, 21, 22, etc.

The source file name is never changed by this method.

Example

This example will show how to use multiple threads to speed up OCR recognition of a multi-page image file. This example shows part of internal functionality already achieved with the IOcrAutoRecognizeManager class.

C#
Visual Basic

Imports Leadtools
Imports Leadtools.Codecs
Imports Leadtools.Forms.DocumentWriters
Imports Leadtools.Forms.Ocr

      
Public Sub AppendLtdExample()
   ' Get a multi-page source file
   Dim inputFileName As String = GetImageFileName()
   Dim outputFileName As String = Path.Combine(LEAD_VARS.ImagesDir, "AppendLtdExample.pdf")
   ' This is the LTD file we will use to append all recognition data
   Dim mainLtdFileName As String = Path.GetTempFileName()

   If (File.Exists(outputFileName)) Then File.Delete(outputFileName)

   If (File.Exists(mainLtdFileName)) Then File.Delete(mainLtdFileName)

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

      ' We can re-use LTD files, so create one
      Dim pageLtdFileName As String = Path.GetTempFileName()

      ' Get number of pages
      Dim pageCount As Integer = ocrEngine.RasterCodecsInstance.GetTotalPages(inputFileName)
      For pageNumber As Integer = 1 To pageCount
         ' OCR this page and save it as LTD
         Console.WriteLine("Processing page {0} of {1}", pageNumber, pageCount)
         RecognizeAndSaveLtd(ocrEngine, inputFileName, pageNumber, pageLtdFileName)

         ' Append this LTD to the main one
         ' Notice, first time, the main LTD does not exist, AppendLtd will
         ' just copy the data over from the source file
         ocrEngine.DocumentWriterInstance.AppendLtd(pageLtdFileName, mainLtdFileName)
      Next

      ' No need for this anymore
      File.Delete(pageLtdFileName)

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

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

Private Shared Sub RecognizeAndSaveLtd(ocrEngine As IOcrEngine, inputFileName As String, pageNumber As Integer, pageLtdFileName As String)
   ' Delete the LTD file if it exists so we can put fresh data in it
   If (File.Exists(pageLtdFileName)) Then File.Delete(pageLtdFileName)

   ' Create an OCR document
   Using ocrDocument As IOcrDocument = ocrEngine.DocumentManager.CreateDocument()
      ' Load the page
      Console.WriteLine("  Loading the page")
      ocrDocument.Pages.AddPages(inputFileName, pageNumber, pageNumber, Nothing)

      Dim ocrPage As IOcrPage = ocrDocument.Pages(0)

      ' Auto-zone it
      Console.WriteLine("  Auto-zoning the page")
      ocrPage.AutoZone(Nothing)

      ' Recognize it
      Console.WriteLine("  Recognizing the page")
      ocrPage.Recognize(Nothing)

      ' Save it
      Console.WriteLine("  Saving the page")
      ocrDocument.Save(pageLtdFileName, DocumentFormat.Ltd, Nothing)
   End Using
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")

   If File.Exists(multiPageImageFileName) Then 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"
Public Const OcrAdvantageRuntimeDir As String = "C:\LEADTOOLS 19\Bin\Common\OcrAdvantageRuntime"
End Class

using Leadtools;
using Leadtools.Codecs;
using Leadtools.Forms.DocumentWriters;
using Leadtools.Forms.Ocr;

public void AppendLtdExample()
{
   // Get a multi-page source file
   var inputFileName = GetImageFileName();
   var outputFileName = Path.Combine(LEAD_VARS.ImagesDir, "AppendLtdExample.pdf");
   // This is the LTD file we will use to append all recognition data
   string mainLtdFileName = Path.GetTempFileName();

   if (File.Exists(outputFileName))
      File.Delete(outputFileName);

   if (File.Exists(mainLtdFileName))
      File.Delete(mainLtdFileName);

   // Use OCR Advantage engine
   using (var ocrEngine = OcrEngineManager.CreateEngine(OcrEngineType.Advantage, false))
   {
      ocrEngine.Startup(null, null, null, LEAD_VARS.OcrAdvantageRuntimeDir);

      // We can re-use LTD files, so create one
      var pageLtdFileName = Path.GetTempFileName();

      // Get number of pages
      var pageCount = ocrEngine.RasterCodecsInstance.GetTotalPages(inputFileName);
      for (var pageNumber = 1; pageNumber <= pageCount; pageNumber++)
      {
         // OCR this page and save it as LTD
         Console.WriteLine("Processing page {0} of {1}", pageNumber, pageCount);
         RecognizeAndSaveLtd(ocrEngine, inputFileName, pageNumber, pageLtdFileName);

         // Append this LTD to the main one
         // Notice, first time, the main LTD does not exist, AppendLtd will
         // just copy the data over from the source file
         ocrEngine.DocumentWriterInstance.AppendLtd(pageLtdFileName, mainLtdFileName);
      }

      // No need for this anymore
      File.Delete(pageLtdFileName);

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

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

private static void RecognizeAndSaveLtd(IOcrEngine ocrEngine, string inputFileName, int pageNumber, string pageLtdFileName)
{
   // Delete the LTD file if it exists so we can put fresh data in it
   if (File.Exists(pageLtdFileName))
      File.Delete(pageLtdFileName);

   // Create an OCR document
   using (var ocrDocument = ocrEngine.DocumentManager.CreateDocument())
   {
      // Load the page
      Console.WriteLine("  Loading the page");
      ocrDocument.Pages.AddPages(inputFileName, pageNumber, pageNumber, null);

      var ocrPage = ocrDocument.Pages[0];

      // Auto-zone it
      Console.WriteLine("  Auto-zoning the page");
      ocrPage.AutoZone(null);

      // Recognize it
      Console.WriteLine("  Recognizing the page");
      ocrPage.Recognize(null);

      // Save it
      Console.WriteLine("  Saving the page");
      ocrDocument.Save(pageLtdFileName, DocumentFormat.Ltd, null);
   }
}

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

   if (File.Exists(multiPageImageFileName))
      File.Delete(multiPageImageFileName);

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

      for (int page = 1; page <= 4; page++)
      {
         var 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";
public const string OcrAdvantageRuntimeDir = @"C:\LEADTOOLS 19\Bin\Common\OcrAdvantageRuntime";
}

Requirements

Target Platforms

Reference

DocumentWriter Class
DocumentWriter Members
DocumentPage Class
DocumentFormat Enumeration
Programming with LEADTOOLS Document Writers
Files to be Included with Your Application
Unlocking Special LEAD Features