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IOcrPage Interface


Defines an image page in an OCR document.

public interface IOcrPage : IDisposable 
Public Interface IOcrPage  
   Inherits System.IDisposable  
@interface LTOcrPage : NSObject 
public class OcrPage 
public interface class IOcrPage : public System.IDisposable   


IOcrPage defines a page currently added in the OCR engine. Each page contains the raster image used to create it (the image used when the page is loaded or added) and a group of OCR zones for the page either added manually or through auto-zoning.

Pages can be stand-alone or part of an IOcrDocument. To create a stand-alone page, use IOcrEngine.CreatePage. To create pages as part of IOcrDocument, use the IOcrDocument.Pages collection.

For information on how to create memory-based or file-based documents or how to load file-based documents from disk refer to IOcrDocumentManager.CreateDocument and Programming with the LEADTOOLS .NET OCR.

Memory-Based Documents

You can access the pages inside a memory-based OCR document (IOcrDocument) through the IOcrDocument.Pages property. The value of this property is a IOcrPageCollection interface. This interface implements standard .NET ICollection<T>, IList<T>, and IEnumerable<T> interfaces and hence, you can use the member of these interfaces to add, remove, get, set and iterate through the different pages of the document.

In memory-based documents, you cannot create IOcrPage objects directly. Instead, add pages to the engine through the various AddPage, AddPages, InsertPage and InsertPages methods of the IOcrPageCollection interface. Once a page is added, access it by index to get the IOcrPage object associated with it.

Pages obtained this way do not need to be disposed. The owner IOcrDocument will automatically destroy the pages when it is disposed.

File-Based Documents

Usually, you create a page directly using IOcrEngine.CreatePage. You can use all the IOcrPage methods to zone and recognize the document as listed below as usual. And if saving the page to a final output format is required, then you can add this page to a file-based IOcrDocument using the IOcrPageCollection.Add member of Pages.

Pages obtained through CreatePage must be destroyed by the user using the Dispose method.

Each page contains a collection of OCR zones. This collection can be accessed with the Zones member. This member implements the IOcrZoneCollection interface which also implements the same standard .NET collections interfaces as IOcrPageCollection. Hence you can use Zones to add, remove, get, set and iterate through the various zones in the page.

After optionally manipulating the zones inside a page, call Recognize to collect the recognition data of the page. This data is stored internally in the page and can later be saved to one of the many document file formats supported by the engine such as PDF or Microsoft Word.

After a page is recognized, examine and modify the recognition data (characters and words) through the GetRecognizedCharacters and SetRecognizedCharacters methods. The GetText method can be used to obtain the recognition data as simple string object.

Once an IOcrPage object is obtained, you can do the following:

  • Get information regarding the page image, such its Width, Height, BitsPerPixel and the DPI (DpiX and DpiY) values.

  • Get a RasterImage object with the GetRasterImage method that represents the page raster image data. Manipulate this image with other parts of LEADTOOLS such as the various image processing commands or show it in the Windows Forms viewer. You can also use SetRasterImage to update the page raster image data.


This example creates an OCR document and adds a page to it, displays various information about the page and then saves it as PDF file.

using Leadtools; 
using Leadtools.Codecs; 
using Leadtools.Ocr; 
using Leadtools.Forms.Common; 
using Leadtools.Document.Writer; 
using Leadtools.WinForms; 
using Leadtools.Drawing; 
using Leadtools.ImageProcessing; 
using Leadtools.ImageProcessing.Color; 
public void OcrPageExample() 
   string tifFileName = Path.Combine(LEAD_VARS.ImagesDir, "Ocr1.tif"); 
   string pdfFileName = Path.Combine(LEAD_VARS.ImagesDir, "Ocr1.pdf"); 
   // Create an instance of the engine 
   using (IOcrEngine ocrEngine = OcrEngineManager.CreateEngine(OcrEngineType.LEAD, false)) 
      // Start the engine using default parameters 
      ocrEngine.Startup(null, null, null, LEAD_VARS.OcrLEADRuntimeDir); 
      // Create an OCR document 
      using (IOcrDocument ocrDocument = ocrEngine.DocumentManager.CreateDocument()) 
         // Add this image to the document 
         IOcrPage ocrPage = ocrDocument.Pages.AddPage(tifFileName, null); 
         // Auto-recognize the zones in the page 
         // Show its information 
         Console.WriteLine("Size: {0} by {1} pixels", ocrPage.Width, ocrPage.Height); 
         Console.WriteLine("Resolution: {0} by {1} dots/inch", ocrPage.DpiX, ocrPage.DpiX); 
         Console.WriteLine("Bits/Pixel: {0}, Bytes/Line: {1}", ocrPage.BitsPerPixel, ocrPage.BytesPerLine); 
         byte[] palette = ocrPage.GetPalette(); 
         int paletteEntries; 
         if (palette != null) 
            paletteEntries = palette.Length / 3; 
            paletteEntries = 0; 
         Console.WriteLine("Number of entries in the palette: {0}", paletteEntries); 
         Console.WriteLine("Original format of this page: {0}", ocrPage.OriginalFormat); 
         Console.WriteLine("Has this page been recognized? : {0}", ocrPage.IsRecognized); 
         // Recognize it and save it as PDF 
         ocrDocument.Save(pdfFileName, DocumentFormat.Pdf, null); 
      // Shutdown the engine 
      // Note: calling Dispose will also automatically shutdown the engine if it has been started 
private void ShowZonesInfo(IOcrPage ocrPage) 
   foreach (OcrZone ocrZone in ocrPage.Zones) 
      int index = ocrPage.Zones.IndexOf(ocrZone); 
      Console.WriteLine("Zone index: {0}", index); 
      Console.WriteLine("  Id                  {0}", ocrZone.Id); 
      Console.WriteLine("  Bounds              {0}", ocrZone.Bounds); 
      Console.WriteLine("  ZoneType            {0}", ocrZone.ZoneType); 
      Console.WriteLine("  CharacterFilters:   {0}", ocrZone.CharacterFilters); 
static class LEAD_VARS 
   public const string ImagesDir = @"C:\Users\Public\Documents\LEADTOOLS Images"; 
   public const string OcrLEADRuntimeDir = @"C:\LEADTOOLS 20\Bin\Common\OcrLEADRuntime"; 
Imports Leadtools 
Imports Leadtools.Codecs 
Imports Leadtools.Ocr 
Imports Leadtools.Forms 
Imports Leadtools.Document.Writer 
Imports Leadtools.WinForms 
Imports Leadtools.Drawing 
Imports Leadtools.ImageProcessing 
Imports Leadtools.ImageProcessing.Color 
Public Sub OcrPageExample() 
   Dim tifFileName As String = Path.Combine(LEAD_VARS.ImagesDir, "Ocr1.tif") 
   Dim pdfFileName As String = Path.Combine(LEAD_VARS.ImagesDir, "Ocr1.pdf") 
   ' Create an instance of the engine 
   Using ocrEngine As IOcrEngine = OcrEngineManager.CreateEngine(OcrEngineType.LEAD, False) 
      ' Start the engine using default parameters 
      ocrEngine.Startup(Nothing, Nothing, Nothing, LEAD_VARS.OcrLEADRuntimeDir) 
      ' Create an OCR document 
      Using ocrDocument As IOcrDocument = ocrEngine.DocumentManager.CreateDocument() 
         ' Add this image to the document 
         Dim ocrPage As IOcrPage = ocrDocument.Pages.AddPage(tifFileName, Nothing) 
         ' Auto-recognize the zones in the page 
         ' Show its information 
         Console.WriteLine("Size: {0} by {1} pixels", ocrPage.Width, ocrPage.Height) 
         Console.WriteLine("Resolution: {0} by {1} dots/inch", ocrPage.DpiX, ocrPage.DpiX) 
         Console.WriteLine("Bits/Pixel: {0}, Bytes/Line: {1}", ocrPage.BitsPerPixel, ocrPage.BytesPerLine) 
         Dim palette As Byte() = ocrPage.GetPalette() 
         Dim paletteEntries As Integer 
         If palette IsNot Nothing Then 
            paletteEntries = palette.Length \ 3 
            paletteEntries = 0 
         End If 
         Console.WriteLine("Number of entries in the palette: {0}", paletteEntries) 
         Console.WriteLine("Original format of this page: {0}", ocrPage.OriginalFormat) 
         Console.WriteLine("Has this page been recognized? : {0}", ocrPage.IsRecognized) 
         ' Recognize it and save it as PDF 
         ocrDocument.Save(pdfFileName, DocumentFormat.Pdf, Nothing) 
      End Using 
      ' Shutdown the engine 
      ' Note: calling Dispose will also automatically shutdown the engine if it has been started 
   End Using 
End Sub 
Private Sub ShowZonesInfo(ocrPage As IOcrPage) 
   For Each ocrZone As OcrZone In ocrPage.Zones 
      Dim index As Integer = ocrPage.Zones.IndexOf(ocrZone) 
      Console.WriteLine("Zone index: {0}", index) 
      Console.WriteLine("  Id                  {0}", ocrZone.Id) 
      Console.WriteLine("  Bounds              {0}", ocrZone.Bounds) 
      Console.WriteLine("  ZoneType            {0}", ocrZone.ZoneType) 
      Console.WriteLine("  CharacterFilters:   {0}", ocrZone.CharacterFilters) 
End Sub 
Public NotInheritable Class LEAD_VARS 
   Public Const ImagesDir As String = "C:\Users\Public\Documents\LEADTOOLS Images" 
   Public Const OcrLEADRuntimeDir As String = "C:\LEADTOOLS 20\Bin\Common\OcrLEADRuntime" 
End Class 


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Leadtools.Ocr Assembly