This example will load multiple-pages into an OCR document and saves the OCR result into a multiple-page PDF file.

Visual Basic

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Public Sub PageCollectionExamples()    ' Unlock the support needed for LEADTOOLS Plus OCR engine    RasterSupport.Unlock(RasterSupportType.Document, "Replace with your own key here")    RasterSupport.Unlock(RasterSupportType.OcrPlus, "Replace with your own key here")    RasterSupport.Unlock(RasterSupportType.OcrPlusPdfLeadOutput, "Replace with your own key here")    ' For this example, we need a multi-page TIF file.    ' Create a muti-page TIF from Ocr1.tif, Ocr2.tif, Ocr3.tif and Ocr4.tif    Dim imagesPath As String = LeadtoolsExamples.Common.ImagesPath.Path + ""    Dim tifFileName As String = Path.Combine(imagesPath, "Ocr.tif")    If (File.Exists(tifFileName)) Then       File.Delete(tifFileName)    End If    RasterCodecs.Startup()    Using codecs As New RasterCodecs()       For i As Integer = 0 To 3          Dim pageFileName As String = Path.Combine(imagesPath, String.Format("Ocr{0}.tif", i + 1))          Using image As RasterImage = codecs.Load(pageFileName)             codecs.Save(image, tifFileName, RasterImageFormat.CcittGroup4, 1, 1, 1, -1, CodecsSavePageMode.Append)          End Using       Next    End Using    RasterCodecs.Shutdown()    Dim pdfFileName As String = LeadtoolsExamples.Common.ImagesPath.Path + "Ocr.pdf"    ' Create an instance of the engine    Using ocrEngine As IOcrEngine = OcrEngineManager.CreateEngine(OcrEngineType.Plus, False)       ' Start the engine using default parameters       ocrEngine.Startup(Nothing, Nothing, Nothing, Nothing)       ' Create an OCR document       Using ocrDocument As IOcrDocument = ocrEngine.DocumentManager.CreateDocument()          ' Load all the pages of the multi-page tif file we created into the document          ocrDocument.Pages.AddPages(tifFileName, 1, -1, Nothing)          Console.WriteLine("{0} pages added to the document", ocrDocument.Pages.Count)          ' Auto-zone          ocrDocument.Pages.AutoZone(Nothing)          ' Recognize          ocrDocument.Pages.Recognize(Nothing)          ' Save          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       ocrEngine.Shutdown()    End Using End Sub

C#

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public void PageCollectionExamples()  {     // Unlock the support needed for LEADTOOLS Plus OCR engine     RasterSupport.Unlock(RasterSupportType.Document, "Replace with your own key here");     RasterSupport.Unlock(RasterSupportType.OcrPlus, "Replace with your own key here");     RasterSupport.Unlock(RasterSupportType.OcrPlusPdfLeadOutput, "Replace with your own key here");     // For this example, we need a multi-page TIF file.     // Create a muti-page TIF from Ocr1.tif, Ocr2.tif, Ocr3.tif and Ocr4.tif     string imagesPath = LeadtoolsExamples.Common.ImagesPath.Path;     string tifFileName = Path.Combine(imagesPath, "Ocr.tif");     if(File.Exists(tifFileName))        File.Delete(tifFileName);       RasterCodecs.Startup();     using(RasterCodecs codecs = new RasterCodecs())     {        for(int i = 0; i < 4; i++)        {           string pageFileName = Path.Combine(imagesPath, string.Format("Ocr{0}.tif", i + 1));           using(RasterImage image = codecs.Load(pageFileName))              codecs.Save(image, tifFileName, RasterImageFormat.CcittGroup4, 1, 1, 1, -1, CodecsSavePageMode.Append);        }     }     RasterCodecs.Shutdown();       string pdfFileName = LeadtoolsExamples.Common.ImagesPath.Path + "Ocr.pdf";       // Create an instance of the engine     using(IOcrEngine ocrEngine = OcrEngineManager.CreateEngine(OcrEngineType.Plus, false))     {        // Start the engine using default parameters        ocrEngine.Startup(null, null, null, null);          // Create an OCR document        using(IOcrDocument ocrDocument = ocrEngine.DocumentManager.CreateDocument())        {           // Load all the pages of the multi-page tif file we created into the form           ocrDocument.Pages.AddPages(tifFileName, 1, -1, null);           Console.WriteLine("{0} pages added to the document", ocrDocument.Pages.Count);             // Auto-zone           ocrDocument.Pages.AutoZone(null);                // Recognize           ocrDocument.Pages.Recognize(null);             // Save           ocrDocument.Save(pdfFileName, DocumentFormat.Pdf, null);        }          // Shutdown the engine        // Note: calling Dispose will also automatically shutdown the engine if it has been started        ocrEngine.Shutdown();     }  }

IOcrPageCollection holds the pages currently added into an OCR document (IOcrDocument). IOcrDocument through the IOcrDocument.Pages holds a collection of IOcrPage object. Each of these IOcrPage objects 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.

The IOcrPageCollection interface implements standard .NET Generic ICollection, Generic IList, and Generic IEnumerable interfaces and hence, you can use the member of these interfaces to add, remove, get, set and iterate through the different pages of the OCR document.

The following list contains the major functionality of the IOcrPageCollection interface:

• Add new pages to an OCR document from raster image files. These files can be in disk files, a .NET stream (memory or otherwise) or even in a remote URL. The following table lists all the page addition method groups:

  Methods	Description
  AddPage	Adds a single page from a RasterImage, DIB or an image file in disk file, .NET stream, remote URL.
  AddPages	Adds multiple pages from a multi-page RasterImage or an image file in disk file, .NET stream or remote URL.
  InsertPage	Inserts into a specific location a single page from a RasterImage, DIB or an image file in disk file, .NET stream, remote URL.
  InsertPages	Inserts into a specific location multiple pages from a multi-page RasterImage or an image file in disk file, .NET stream or remote URL.

• Export pages from the OCR document to raster image files. You can save the pages in disk files, .NET streams or as a single or multi-page RasterImage object with any of the file formats supported by LEADTOOLS. The following table list all the page exporting method groups:

  Methods	Description
  ExportPage	Saves a single page from the OCR document to a RasterImage object, an image file in disk file or a .NET stream.
  ExportPages	Saves multiple pages from the OCR document to a multi-page RasterImage object, an image file in disk file or a .NET stream.

• Perform auto image preprocessing on a single or multiple pages in the OCR document through AutoPreprocess. These methods provide a shortcut for iterating through the pages in the collection and calling IOcrPage.AutoPreprocess on each page.
• Perform auto-zoning on a single or multiple pages in the OCR document through AutoZone. These methods provide a shortcut for iterating through the pages in the collection and calling IOcrPage.AutoZone on each page.
• Update the type of text in the zones of on a single or multiple pages in the OCR document through UpdateFillMethod. These methods provide a shortcut for iterating through the pages in the collection and calling IOcrPage.UpdateFillMethod on each page.
• Recognize a single or multiple pages in the OCR document through Recognize. These methods provide a shortcut for iterating through the pages in the collection and calling IOcrPage.Recognize on each page.

The LEADTOOLS OCR engine supports pages of dots per inch (DPI) values of 150 and greater. If you try to add a page with a DPI of less than 150 then the engine might be able to recognize any data from this page.

Note, the LEADTOOLS Plus OCR engine does not support image size greater than A3 paper size (11.7 by 16.5 inches at 300 dpi). Attempting to add an image that has a size greater than A3 will result in an error. For document of size greater than the maximum allowed, you must first resize the image before adding it to the LEADTOOLS Plus OCR engine. The Professional and Advantage engines do not have a restriction on the image size.

Target Platforms: Microsoft .NET Framework 3.0, Windows XP, Windows Server 2003 family, Windows Server 2008 family

Reference