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AppendLtd Method

Summary

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

Syntax

C#
VB
Java
Objective-C
C++
public void AppendLtd( 
   string sourceFileName, 
   string destFileName 
) 
Public Sub AppendLtd( _ 
   ByVal sourceFileName As String, _ 
   ByVal destFileName As String _ 
)  
- (BOOL)appendLtdFile:(NSString *)srcLtdFile  
   destinationLtdFile:(NSString *)dstLtdFile  
                error:(NSError **)error 
             
public void appendLtd(String sourceFileName, String destFileName) 
public: 
void AppendLtd(  
   String^ sourceFileName, 
   String^ 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 exist 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#
VB
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"; 
} 
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 

Requirements

Target Platforms

Help Version 19.0.2017.10.18
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Leadtools.Forms.DocumentWriters Assembly