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OCR Tutorial - Working with Recognition Results

Take the following steps to create and run a program that shows how to interactively draw zones on an OCR page and how to recognize these zones. Remember, the purpose of the tutorials is to provide you with a quick and easy way to generate an OCR program.

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 "VB Projects" in the Projects Type List, and choose "Windows Application" or "Windows Forms Application" depending on your Visual Studio version from the Templates List.
Type the project name as "OcrTutorial2" 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\DotNet4\Win32" folder and select the following DLLs:
- Leadtools.dll
- Leadtools.Drawing.dll
- Leadtools.Codecs.dll
- Leadtools.Controls.WinForms.dll
- Leadtools.Forms.Common.dll
- Leadtools.Document.Writer.dll
- Leadtools.Ocr.dll
- Leadtools.Ocr.LEADEngine.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.

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 using or Imports section if there are any:

      using Leadtools; 
      using Leadtools.Codecs; 
      using Leadtools.Drawing; 
      using Leadtools.Controls; 
      using Leadtools.Forms.Common; 
      using Leadtools.Ocr; 
      using Leadtools.Document.Writer;

      Imports Leadtools 
      Imports Leadtools.Codecs 
      Imports Leadtools.Drawing 
      Imports Leadtools.Controls 
      Imports Leadtools.Forms.Common 
      Imports Leadtools.Ocr 
      Imports Leadtools.Document.Writer

Add the following private variables to the Form1 class:

      // Image viewer instance 
      private ImageViewer _imageViewer; 
      // The OCR engine instance 
      private IOcrEngine _ocrEngine; 
      // The OCR page 
      private IOcrPage _ocrPage; 
      // Recognition results (characters with bounds information) 
      private IOcrZoneCharacters _zoneCharacters;

      ' Image viewer instance 
      Private _imageViewer As ImageViewer 
      ' The OCR engine instance 
      Private _ocrEngine As IOcrEngine 
      ' The OCR page 
      Private _ocrPage As IOcrPage 
      ' Recognition results (characters with bounds information) 
      Private _zoneCharacters As IOcrZoneCharacters

Override Form1OnLoad and add the following code:

      protected override void OnLoad(EventArgs e) 
      { 
         string MY_LICENSE_FILE = @"C:\LEADTOOLS 20\Support\Common\License\leadtools.lic"; 
         string MY_DEVELOPER_KEY = System.IO.File.ReadAllText(@"C:\LEADTOOLS 20\Support\Common\License\leadtools.lic.key"); 
 
         RasterSupport.SetLicense(MY_LICENSE_FILE, MY_DEVELOPER_KEY); 
 
         // Add the image viewer to the form 
         _imageViewer = new ImageViewer(); 
         _imageViewer.Dock = DockStyle.Fill; 
         Controls.Add(_imageViewer); 
         _imageViewer.BringToFront(); 
         // Show images using their true size 
         _imageViewer.UseDpi = true; 
                 
         // Add ability to pan/zoom using the left mouse button 
         ImageViewerPanZoomInteractiveMode panZoomMode = new ImageViewerPanZoomInteractiveMode(); 
         panZoomMode.MouseButtons = MouseButtons.Left; 
         _imageViewer.InteractiveModes.Add(panZoomMode); 
         // Add a rubber band mode to the right mouse button 
         ImageViewerRubberBandInteractiveMode rubbBandMode = new ImageViewerRubberBandInteractiveMode(); 
         rubbBandMode.MouseButtons = MouseButtons.Right; 
         // Hook to the rubber-band completed event so we can recognize that area 
         rubbBandMode.RubberBandCompleted += rubbBandMode_RubberBandCompleted; 
         _imageViewer.InteractiveModes.Add(rubbBandMode); 
                 
         // Initialize the OCR engine 
         _ocrEngine = OcrEngineManager.CreateEngine(OcrEngineType.LEAD, false); 
         // Startup the engine 
         _ocrEngine.Startup(null, null, null, @"C:\LEADTOOLS 20\Bin\Common\OcrLEADRuntime"); 
         // Create the OCR page from an image 
         string fileName = @"C:\Users\Public\Documents\LEADTOOLS Images\Ocr1.tif"; 
         RasterImage rasterImage = _ocrEngine.RasterCodecsInstance.Load(fileName, 1); 
         _ocrPage = _ocrEngine.CreatePage(rasterImage, OcrImageSharingMode.AutoDispose); 
         // Show this image in the viewer 
         _imageViewer.Image = _ocrPage.GetRasterImage(); 
         Text = "Left click and drag to pan, CTRL-Left and drag click to zoom, right click and draw to draw the selection rectangle"; 
                 
         // Hook to the post render event of the viewer so we can render the recognition result on the page 
         _imageViewer.PostRender += _imageViewer_PostRender; 
                 
         base.OnLoad(e); 
      }

      Protected Overrides Sub OnLoad(e As EventArgs) 
        ' Requires a license file that unlocks 1D barcode read functionality. 
         Dim MY_LICENSE_FILE As String = "C:\LEADTOOLS 20\Support\Common\License\leadtools.lic" 
         Dim MY_DEVELOPER_KEY As String = System.IO.File.ReadAllText("C:\LEADTOOLS 20\Support\Common\License\leadtools.lic.key") 
         RasterSupport.SetLicense(MY_LICENSE_FILE, MY_DEVELOPER_KEY) 
 
         ' Add the image viewer to the form 
         _imageViewer = New ImageViewer() 
         _imageViewer.Dock = DockStyle.Fill 
         Controls.Add(_imageViewer) 
         _imageViewer.BringToFront() 
         ' Show images using their true size 
         _imageViewer.UseDpi = True 
                  
         ' Add ability to pan/zoom using the left mouse button 
         Dim panZoomMode As New ImageViewerPanZoomInteractiveMode() 
         panZoomMode.MouseButtons = MouseButtons.Left 
         _imageViewer.InteractiveModes.Add(panZoomMode) 
         ' Add a rubber band mode to the right mouse button 
         Dim rubbBandMode As New ImageViewerRubberBandInteractiveMode() 
         rubbBandMode.MouseButtons = MouseButtons.Right 
         ' Hook to the rubber-band completed event so we can recognize that area 
         AddHandler rubbBandMode.RubberBandCompleted, AddressOf rubbBandMode_RubberBandCompleted 
         _imageViewer.InteractiveModes.Add(rubbBandMode) 
                  
         ' Initialize the OCR engine 
         _ocrEngine = OcrEngineManager.CreateEngine(OcrEngineType.LEAD, False) 
         ' Startup the engine 
         _ocrEngine.Startup(Nothing, Nothing, Nothing, "C:\LEADTOOLS 20\Bin\Common\OcrLEADRuntime") 
         ' Create the OCR page from an image 
         Dim fileName As String = "C:\Users\Public\Documents\LEADTOOLS Images\Ocr1.tif" 
         Dim rasterImage As RasterImage = _ocrEngine.RasterCodecsInstance.Load(fileName, 1) 
         _ocrPage = _ocrEngine.CreatePage(rasterImage, OcrImageSharingMode.AutoDispose) 
         ' Show this image in the viewer 
         _imageViewer.Image = _ocrPage.GetRasterImage() 
         Text = "Left click and drag to pan, CTRL-Left and drag click to zoom, right click and draw to draw the selection rectangle" 
                  
         ' Hook to the post render event of the viewer so we can render the recognition result on the page 
         AddHandler _imageViewer.PostRender, AddressOf _imageViewer_PostRender 
                  
         MyBase.OnLoad(e) 
      End Sub

Override Form1OnFormClosed and add the following code:

      protected override void OnFormClosed(FormClosedEventArgs e) 
      { 
         // Destroy the page 
         _ocrPage.Dispose(); 
                    
         // And the engine 
         _ocrEngine.Dispose(); 
                    
         base.OnFormClosed(e); 
      }

      Protected Overrides Sub OnFormClosed(e As FormClosedEventArgs) 
         ' Destroy the page 
         _ocrPage.Dispose() 
                 
         ' And the engine 
         _ocrEngine.Dispose() 
                 
         MyBase.OnFormClosed(e) 
      End Sub

Add the following code to handle the rubber band completed event. Draw the zone and recognize it:

      private void rubbBandMode_RubberBandCompleted(object sender, ImageViewerRubberBandEventArgs e) 
      { 
         // Use has drawn a selection rectangle 
                 
         // Remove current zone from the page 
         _ocrPage.Zones.Clear(); 
                 
         // Add the new zone. The points from rubber band is in control coordinates, need to convert them to image 
         LeadRect bounds = LeadRect.FromLTRB(e.Points[0].X, e.Points[0].Y, e.Points[1].X, e.Points[1].Y); 
         bounds = _imageViewer.ConvertRect(null, ImageViewerCoordinateType.Control, ImageViewerCoordinateType.Image, bounds); 
                 
         // Add a new text zone from these coordinates 
         OcrZone ocrZone = new OcrZone(); 
         ocrZone.ZoneType = OcrZoneType.Text; 
         ocrZone.Bounds = bounds; 
         _ocrPage.Zones.Add(ocrZone); 
                 
         // Recognize the page to get the text of the zone 
         _ocrPage.Recognize(null); 
                 
         // Get the recognized characters 
         IOcrPageCharacters pageCharacters = _ocrPage.GetRecognizedCharacters(); 
         _zoneCharacters = pageCharacters[0]; 
                 
         // Refresh the viewer so we render the character bounds and positions 
         _imageViewer.Refresh(); 
                 
         // Show the result in a message box 
         string text = _ocrPage.GetText(0); 
         if (string.IsNullOrEmpty(text)) 
            text = "[Nothing found]"; 
         MessageBox.Show(this, text); 
      }

      Private Sub rubbBandMode_RubberBandCompleted(sender As Object, e As ImageViewerRubberBandEventArgs) 
         ' Use has drawn a selection rectangle 
                 
         ' Remove the current zone from the page 
         _ocrPage.Zones.Clear() 
                 
         ' Add the new zone. The points from rubber band is in control coordinates, need to convert them to image 
         Dim bounds As LeadRect = LeadRect.FromLTRB(e.Points(0).X, e.Points(0).Y, e.Points(1).X, e.Points(1).Y) 
         bounds = _imageViewer.ConvertRect(Nothing, ImageViewerCoordinateType.Control, ImageViewerCoordinateType.Image, bounds) 
                 
         ' Add a new text zone from these coordinates 
         Dim ocrZone As New OcrZone() 
         ocrZone.ZoneType = OcrZoneType.Text 
         ocrZone.Bounds = bounds 
         _ocrPage.Zones.Add(ocrZone) 
                 
         ' Recognize the page to get the text of the zone 
         _ocrPage.Recognize(Nothing) 
                 
         ' Get the recognized characters 
         Dim pageCharacters As IOcrPageCharacters = _ocrPage.GetRecognizedCharacters() 
         _zoneCharacters = pageCharacters(0) 
                 
         ' Refresh the viewer so we render the character bounds and positions 
         _imageViewer.Refresh() 
                 
         ' Show the result in a message box 
         Dim text As String = _ocrPage.GetText(0) 
         If String.IsNullOrEmpty(text) Then 
            text = "[Nothing found]" 
         End If 
         MessageBox.Show(Me, text) 
      End Sub

Finally (optional) add the following code to handle the image viewer post render event. Render the characters:

      private void _imageViewer_PostRender(object sender, ImageViewerRenderEventArgs e) 
      { 
         // Draw the recognition results (if we have any) 
         if (_zoneCharacters == null) 
            return; 
                 
         Graphics graphics = e.PaintEventArgs.Graphics; 
                 
         using (Brush characterBrush = new SolidBrush(Color.FromArgb(128, Color.Black))) 
         { 
            foreach (OcrCharacter character in _zoneCharacters) 
            { 
               // Get the character boundary 
               LeadRect bounds = character.Bounds; 
               // Convert the bound to what we see in the viewer 
               // Note that this demo does not have rotation; otherwise, you need to use the four corner points 
               bounds = _imageViewer.ConvertRect(null, ImageViewerCoordinateType.Image, ImageViewerCoordinateType.Control, bounds); 
                 
               // Highlight the character area on the page 
               graphics.FillRectangle(characterBrush, bounds.X, bounds.Y, bounds.Width, bounds.Height); 
               graphics.DrawRectangle(Pens.Black, bounds.X, bounds.Y, bounds.Width - 1, bounds.Height - 1); 
                 
               // Finally draw the character code it self 
               graphics.DrawString(new string(new char[] { character.Code }), this.Font, Brushes.White, bounds.X, bounds.Y); 
            } 
         } 
      }

      Private Sub _imageViewer_PostRender(sender As Object, e As ImageViewerRenderEventArgs) 
         ' Draw the recognition results (if we have any) 
         If IsNothing(_zoneCharacters) Then Return 
                 
         Dim graphics As Graphics = e.PaintEventArgs.Graphics 
                 
         Using characterBrush As New SolidBrush(Color.FromArgb(128, Color.Black)) 
            For Each character As OcrCharacter In _zoneCharacters 
               ' Get the character boundary 
               Dim bounds As LeadRect = character.Bounds 
               ' Convert the bound to what we see in the viewer 
               ' Note that this demo does not have rotation; otherwise, you need to use the four corner points 
               bounds = _imageViewer.ConvertRect(Nothing, ImageViewerCoordinateType.Image, ImageViewerCoordinateType.Control, bounds) 
                 
               ' Highlight the character area on the page 
               graphics.FillRectangle(characterBrush, bounds.X, bounds.Y, bounds.Width, bounds.Height) 
               graphics.DrawRectangle(Pens.Black, bounds.X, bounds.Y, bounds.Width - 1, bounds.Height - 1) 
                 
               ' Finally draw the character code it self 
               graphics.DrawString(New String(New Char() {character.Code}), Me.Font, Brushes.White, bounds.X, bounds.Y) 
            Next 
         End Using 
      End Sub