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OCR Tutorial - Scanning to Searchable PDF

Take the following steps to create and run a program that shows how scan a document and convert it to a searchable PDF file.

  1. Start Visual Studio 2005 or 2008

  2. Choose File->New->Project from the menu

  3. In the New Project dialog box, choose either "Visual C# Projects" or "Visual Basic Projects" in the Projects Type List, and choose "Windows Application" in Visual Studio 2005 or "Windows Forms Application" in Visual Studio 2008 from the Templates List

  4. Type the project name as "OcrTutorial3" in the Project Name field, and then choose OK. If desired, type a new location for your project or select a directory using the Browse button, and then choose OK.

  5. In the "Solution Explorer" window, right-click on the "References" folder, and select "Add Reference..." from the context menu. In the "Add Reference" dialog box, select the ".NET" tab and browse to LEADTOOLS For .NET "\LEAD Technologies\LEADTOOLS xx\Bin\DotNet\Win32" folder and select the following DLLs:

    • Leadtools.dll
    • Leadtools.Codecs.dll
    • Leadtools.Forms.dll
    • Leadtools.Forms.DocumentWriters.dll
    • Leadtools.Forms.Ocr.dll
    • Leadtools.Forms.Ocr.Plus.dll
    • Leadtools.Twain.dll
    • Leadtools.ImageProcessing.Core.dll
    • Leadtools.Codecs.Bmp.dll
    • Leadtools.Codecs.Cmp.dll
    • Leadtools.Codecs.Tif.dll
    • Leadtools.Codecs.Fax.dll

    Note: The Leadtools.Codecs.*.dll references added are for the BMP, JPG, CMP, TIF and FAX image file formats. Add any additional file format codec DLL if required in your application.

  6. Drag and drop three buttons in Form1. Leave all the buttons names as the default "button1, button2 ...", then change the Text property of each button to the following:

    Button Text button1 Change output directory button2 Select the Scanner button3 Scan and OCR

  7. Switch to Form1 code view (Right-click Form1 in the solution explorer then select View Code) and add the following lines at the beginning of the file after any Importsor usingsection if there are any:

    [Visual Basic]

          
    
                Imports Leadtools
                Imports Leadtools.Codecs
                Imports Leadtools.Twain
                Imports Leadtools.Forms
                Imports Leadtools.Forms.DocumentWriters
                Imports Leadtools.Forms.Ocr
                Imports Leadtools.ImageProcessing.Core
                     
                
    
    
        
    

    [C#]

          
    
                using Leadtools;
                using Leadtools.Codecs;
                using Leadtools.Twain;
                using Leadtools.Forms;
                using Leadtools.Forms.DocumentWriters;
                using Leadtools.Forms.Ocr;
                using Leadtools.ImageProcessing.Core;
                     
                
    
    
        
    
  8. Add the following private variables to the Form1 class:

    [Visual Basic]

          
    
                ' The OCR engine instance
                Private _ocrEngine As IOcrEngine
                ' The OCR document
                Private _ocrDocument As IOcrDocument
                ' The Twain session
                Private _twainSession As TwainSession
                ' The output directory for saving PDF files
                Private _outputDirectory As String = "C:\MyImages"
                ' The image processing commands we are going to use to clean the scanned image
                Private deskewCmd As DeskewCommand
                Private despeckleCmd As DespeckleCommand
                Private dotRemoveCmd As DotRemoveCommand
                Private holePunchRemoveCmd As HolePunchRemoveCommand
                Private lineRemoveCmd As LineRemoveCommand
                     
                
    
    
        
    

    [C#]

          
    
                // The OCR engine instance
                private IOcrEngine _ocrEngine;
                // The OCR document
                private IOcrDocument _ocrDocument;
                // The Twain session
                private TwainSession _twainSession;
                // The output directory for saving PDF files
                private string _outputDirectory = @"C:\MyImages";
                // The image processing commands we are going to use to clean the scanned image
                private DeskewCommand deskewCmd;
                private DespeckleCommand despeckleCmd;
                private DotRemoveCommand dotRemoveCmd;
                private HolePunchRemoveCommand holePunchRemoveCmd;
                private LineRemoveCommand lineRemoveCmd;
                     
                
    
    
        
    
  9. Add the following code to the Form1 constructor (in Visual Basic, you can copy/paste the whole Sub New code from here):

    [Visual Basic]

          
    
                Sub New()
                   ' This call is required by the Windows Form Designer.
                   InitializeComponent()
                   ' Add any initialization after the InitializeComponent() call.
                   ' Unlock the OCR support
                   RasterSupport.Unlock(RasterSupportType.OcrPlus, "testkey")
                   ' Unlock the PDF save support
                   RasterSupport.Unlock(RasterSupportType.OcrPlusPdfLeadOutput, "testkey")
                   ' Unlock Document support
                   RasterSupport.Unlock(RasterSupportType.Document, "testkey")
                   ' Initialize the OCR engine
                   _ocrEngine = OcrEngineManager.CreateEngine(OcrEngineType.Plus, False)
                   ' Startup the engine
                   _ocrEngine.Startup(Nothing, Nothing, Nothing, Nothing)
                   ' Create the OCR document
                   _ocrDocument = _ocrEngine.DocumentManager.CreateDocument()
                   ' Initalize Twain scanning session
                   _twainSession = New TwainSession()
                   _twainSession.Startup(Me, "My Company", "My Product", "My Version", "My Application", TwainStartupFlags.None)
                   ' Subscribe to the TwainSession.Acquire event to get the image
                   AddHandler _twainSession.AcquirePage, AddressOf _twainSession_AcquirePage
                   ' Initialize the image processing commands we are going to use
                   ' Initialize Deskew
                   deskewCmd = New DeskewCommand()
                   ' Initialize Despeckle
                   despeckleCmd = New DespeckleCommand()
                   ' Initialize DotRemove
                   dotRemoveCmd = New DotRemoveCommand()
                   dotRemoveCmd.Flags = _
                      DotRemoveCommandFlags.UseDiagonals Or _
                      DotRemoveCommandFlags.UseSize
                   dotRemoveCmd.MaximumDotHeight = 8
                   dotRemoveCmd.MaximumDotWidth = 8
                   dotRemoveCmd.MinimumDotHeight = 2
                   dotRemoveCmd.MinimumDotWidth = 2
                   ' Initialize HolePunchRemove
                   holePunchRemoveCmd = New HolePunchRemoveCommand()
                   holePunchRemoveCmd.Flags = _
                      HolePunchRemoveCommandFlags.UseDpi Or _
                      HolePunchRemoveCommandFlags.UseCount Or _
                      HolePunchRemoveCommandFlags.UseLocation
                   holePunchRemoveCmd.Location = HolePunchRemoveCommandLocation.Left
                   ' Initialize LineRemove
                   lineRemoveCmd = New LineRemoveCommand()
                   lineRemoveCmd.MaximumLineWidth = 9
                   lineRemoveCmd.MinimumLineLength = 400
                   lineRemoveCmd.Wall = 15
                   lineRemoveCmd.MaximumWallPercent = 10
                   lineRemoveCmd.Variance = 3
                   lineRemoveCmd.GapLength = 3
                End Sub
                     
                
    
    
        
    

    [C#]

          
    
                public Form1()
                {
                   InitializeComponent();
                   // Unlock the OCR support
                   RasterSupport.Unlock(RasterSupportType.OcrPlus, "Replace with your own key here");
                   // Unlock the PDF save support
                   RasterSupport.Unlock(RasterSupportType.OcrPlusPdfLeadOutput, "Replace with your own key here");
                   // Unlock Document support
                   RasterSupport.Unlock(RasterSupportType.Document, "Replace with your own key here");
                   // Initialize the OCR engine
                   _ocrEngine = OcrEngineManager.CreateEngine(OcrEngineType.Plus, false);
                   // Startup the engine
                   _ocrEngine.Startup(null, null, null, null);
                   // Create the OCR document
                   _ocrDocument = _ocrEngine.DocumentManager.CreateDocument();
                   // Initalize Twain scanning session
                   _twainSession = new TwainSession();
                   _twainSession.Startup(this, "My Company", "My Product", "My Version", "My Application", TwainStartupFlags.None);
                   // Subscribe to the TwainSession.Acquire event to get the image
                   _twainSession.AcquirePage += new EventHandler<TwainAcquirePageEventArgs>(_twainSession_AcquirePage);
                   // Initialize the image processing commands we are going to use
                   // Initialize Deskew
                   deskewCmd = new DeskewCommand();
                   // Initialize Despeckle
                   despeckleCmd = new DespeckleCommand();
                   // Initialize DotRemove
                   dotRemoveCmd = new DotRemoveCommand();
                   dotRemoveCmd.Flags =
                      DotRemoveCommandFlags.UseDiagonals |
                      DotRemoveCommandFlags.UseSize;
                   dotRemoveCmd.MaximumDotHeight = 8;
                   dotRemoveCmd.MaximumDotWidth = 8;
                   dotRemoveCmd.MinimumDotHeight = 2;
                   dotRemoveCmd.MinimumDotWidth = 2;
                    // Initialize HolePunchRemove
                   holePunchRemoveCmd = new HolePunchRemoveCommand();
                   holePunchRemoveCmd.Flags =
                      HolePunchRemoveCommandFlags.UseDpi |
                      HolePunchRemoveCommandFlags.UseCount |
                      HolePunchRemoveCommandFlags.UseLocation;
                   holePunchRemoveCmd.Location = HolePunchRemoveCommandLocation.Left;
                   // Initialize LineRemove
                   lineRemoveCmd = new LineRemoveCommand();
                   lineRemoveCmd.MaximumLineWidth = 9;
                   lineRemoveCmd.MinimumLineLength = 400;
                   lineRemoveCmd.Wall = 15;
                   lineRemoveCmd.MaximumWallPercent = 10;
                   lineRemoveCmd.Variance = 3;
                   lineRemoveCmd.GapLength = 3;
                }
                     
                
    
    
        
    
  10. Override the Form1 closed event to add the code necessary to shutdown the OCR engine when the application terminates:

    [Visual Basic]

          
    
                Protected Overrides Sub OnFormClosed(ByVal e As FormClosedEventArgs)
                   ' Destroy the OCR document
                   _ocrDocument.Dispose()
                   ' Shutdown and dispose the OCR engine
                   _ocrEngine.Dispose()
                   ' Close the Twain session
                   _twainSession.Shutdown()
                   MyBase.OnFormClosed(e)
                End Sub
                     
                
    
    
        
    

    [C#]

          
    
                protected override void OnFormClosed(FormClosedEventArgs e)
                {
                   // Destroy the OCR document
                   _ocrDocument.Dispose();
                   // Shutdown and dispose the OCR engine
                   _ocrEngine.Dispose();
                   // Close the Twain session
                   _twainSession.Shutdown();
                   base.OnFormClosed(e);
                }
                     
                
    
    
        
    
  11. Add the following code for the button1 (Change output directory) control’s Clickhandler:

    [Visual Basic]

          
    
                Private Sub button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles button1.Click
                   ' Change the output directory
                   Dim dlg As New FolderBrowserDialog()
                   dlg.SelectedPath = _outputDirectory
                   dlg.ShowNewFolderButton = True
                   If (dlg.ShowDialog(Me) = DialogResult.OK) Then
                      _outputDirectory = System.IO.Path.GetFullPath(dlg.SelectedPath)
                   End If
                End Sub
                     
                
    
    
        
    

    [C#]

          
    
                private void button1_Click(object sender, EventArgs e)
                {
                   // Change the output directory
                   FolderBrowserDialog dlg = new FolderBrowserDialog();
                   dlg.SelectedPath = _outputDirectory;
                   dlg.ShowNewFolderButton = true;
                   if(dlg.ShowDialog(this) == DialogResult.OK)
                      _outputDirectory = System.IO.Path.GetFullPath(dlg.SelectedPath);
                }
                     
                
    
    
        
    
  12. Add the following code for the button2 (Select the Scanner) control’s Clickhandler:

    [Visual Basic]

          
    
                Private Sub button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles button2.Click
                   ' Select the scanner to use
                   _twainSession.SelectSource(Nothing)
                End Sub
                     
                
    
    
        
    

    [C#]

          
    
                private void button2_Click(object sender, EventArgs e)
                {
                   // Select the scanner to use
                   _twainSession.SelectSource(null);
                }
                     
                
    
    
        
    
  13. Add the following code for the button3 (Scan and OCR) control’s Clickhandler:

    [Visual Basic]

          
    
                Private Sub button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles button3.Click
                   ' Create the output directory if it does not exist
                   If (Not System.IO.Directory.Exists(_outputDirectory)) Then
                      System.IO.Directory.CreateDirectory(_outputDirectory)
                   End If
                   ' Build the output PDF file name
                   Dim pdfFileName As String = System.IO.Path.Combine(_outputDirectory, "Scanned.pdf")
                   ' First remove all the pages added to the OCR document
                   _ocrDocument.Pages.Clear()
                   ' Scan the new page(s)
                   _twainSession.Acquire(TwainUserInterfaceFlags.Show)
                   ' The pages should be added to the OCR document now.
                   ' Recognize and save as PDF
                   _ocrDocument.Pages.Recognize(Nothing)
                   _ocrDocument.Save(pdfFileName, DocumentFormat.Pdf, Nothing)
                   ' Show the result PDF file
                   System.Diagnostics.Process.Start(pdfFileName)
                End Sub
                     
                
    
    
        
    

    [C#]

          
    
                private void button3_Click(object sender, EventArgs e)
                {
                   // Create the output directory if it does not exist
                   if(!System.IO.Directory.Exists(_outputDirectory))
                      System.IO.Directory.CreateDirectory(_outputDirectory);
                   // Build the output PDF file name
                   string pdfFileName = System.IO.Path.Combine(_outputDirectory, "Scanned.pdf");
                   // First remove all the pages added to the OCR document
                   _ocrDocument.Pages.Clear();
                   // Scan the new page(s)
                   _twainSession.Acquire(TwainUserInterfaceFlags.Show);
                   // The pages should be added to the OCR document now.
                   // Recognize and save as PDF
                   _ocrDocument.Pages.Recognize(null);
                   _ocrDocument.Save(pdfFileName, DocumentFormat.Pdf, null);
                   // Show the result PDF file
                   System.Diagnostics.Process.Start(pdfFileName);
                }
                     
                
    
    
        
    
  14. Add the private method to handle the AcquirePageevent of the TwainSessionobject:

    [Visual Basic]

          
    
                Private Sub _twainSession_AcquirePage(ByVal sender As Object, ByVal e As TwainAcquirePageEventArgs)
                   ' We have a page
                   Dim image As RasterImage = e.Image
                   ' First, run the image processing commands on it
                   ' Deskew
                   deskewCmd.Run(image)
                   ' Despeckle
                   despeckleCmd.Run(image)
                   ' The rest of the commands only work on 1 BPP image
                   If (image.BitsPerPixel = 1) Then
                      ' Dot Remove
                      dotRemoveCmd.Run(image)
                      ' Hole Punch Remove
                      holePunchRemoveCmd.Run(image)
                      ' Vertical Line Remove
                      lineRemoveCmd.Type = LineRemoveCommandType.Vertical
                      lineRemoveCmd.Run(image)
                      ' Horizontal Line Remove
                      lineRemoveCmd.Type = LineRemoveCommandType.Horizontal
                      lineRemoveCmd.Run(image)
                   End If
                   ' Add the image as a new page to the OCR document
                   _ocrDocument.Pages.AddPage(image, Nothing)
                End Sub
                     
                
    
    
        
    

    [C#]

          
    
                private void _twainSession_AcquirePage(object sender, TwainAcquirePageEventArgs e)
                {
                   // We have a page
                   RasterImage image = e.Image;
                   // First, run the image processing commands on it
                   // Deskew
                   deskewCmd.Run(image);
                   // Despeckle
                   despeckleCmd.Run(image);
                   // The rest of the commands only work on 1 BPP image
                   if(image.BitsPerPixel == 1)
                   {
                      // Dot Remove
                      dotRemoveCmd.Run(image);
                      // Hole Punch Remove
                      holePunchRemoveCmd.Run(image);
                      // Vertical Line Remove
                      lineRemoveCmd.Type = LineRemoveCommandType.Vertical;
                      lineRemoveCmd.Run(image);
                      // Horizontal Line Remove
                      lineRemoveCmd.Type = LineRemoveCommandType.Horizontal;
                      lineRemoveCmd.Run(image);
                   }
                   // Add the image as a new page to the OCR document
                   _ocrDocument.Pages.AddPage(image, null);
                }
                     
                
    
    
        
    
  15. Build, and Run the program to test it. You can click the buttons in the following order to create the PDF file "Startup", "Add Page", "Save and Recognize", "Shutdown".