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OCR Tutorial - Scanning to Searchable PDF
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Take the following steps to create and run a program that shows how scan a document and convert it to a searchable PDF file.
Start Visual Studio 2005 or 2008
Choose File->New->Project from the menu
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
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.
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 "<LEADTOOLS_INSTALLDIR>\Bin\DotNet\Win32" folder and select the following DLLs:
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.
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:
ButtonTextbutton1Change output directorybutton2Select the Scannerbutton3Scan and OCR
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;
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;
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.
' Set LEADTOOLS Runtime license
Dim MY_LICENSE_FILE As String = "d:\temp\TestLic.lic"
Dim MY_DEVELOPER_KEY As String = "xyz123abc"
RasterSupport.SetLicense(MY_LICENSE_FILE, MY_DEVELOPER_KEY)
' Initialize the OCR engine
_ocrEngine = OcrEngineManager.CreateEngine(OcrEngineType.Advantage, False)
' Startup the engine
_ocrEngine.Startup(Nothing, Nothing, Nothing, "C:\LEADTOOLS 18\Bin\Common\OcrAdvantageRuntime")
' 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 Professional support
string MY_LICENSE_FILE = "d:\\temp\\TestLic.lic";
string MY_OCRPRODEVELOPER_KEY = "xyz123abc";
RasterSupport.SetLicense(MY_LICENSE_FILE, MY_OCRPRODEVELOPER_KEY);
// Unlock the PDF save support
string MY_OCRPDFDEVELOPER_KEY = "abc123xyz";
RasterSupport.SetLicense(MY_LICENSE_FILE, MY_OCRPDFDEVELOPER_KEY);
// Unlock Document support
string MY_DOCDEVELOPER_KEY = "123xyzabc";
RasterSupport.SetLicense(MY_LICENSE_FILE, MY_DOCDEVELOPER_KEY);
// Initialize the OCR engine
_ocrEngine = OcrEngineManager.CreateEngine(OcrEngineType.Advantage, false);
// Startup the engine
_ocrEngine.Startup(null, null, null, @"C:\LEADTOOLS 18\Bin\Common\OcrAdvantageRuntime");
// 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;
}
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);
}
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);
}
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);
}
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);
}
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);
}
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".
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