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AddDib Method

Summary

Adds a page from a DIB (Device-independent bitmap) stored in unmanaged memory.

Syntax

C#
VB
C++
public IOcrPage AddDib( 
   IntPtr dib, 
   OcrProgressCallback callback 
) 
Overloads Function AddDib( _ 
   ByVal dib As IntPtr, _ 
   ByVal callback As Leadtools.Ocr.OcrProgressCallback _ 
) As Leadtools.Ocr.IOcrPage 

Parameters

dib
An unmanaged pointer to the DIB (device-independent bitmap).

callback
Optional callback to show operation progress.

Return Value

The IOcrPage object that define the newly added page.

Remarks

This method will add a device independent bitmap (DIB) stored in an unmanaged memory pointer to the OCR document.

This method will add the page to the end of the collection if you already have pages in this IOcrPageCollection.

You can use the OcrProgressCallback to show the operation progress or to abort it. For more information and an example, refer to OcrProgressCallback.

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 value of the "Recognition.ShareOriginalImage" (only supported by the LEADTOOLS OCR Module - LEAD Engine) setting is not used when calling this method. The engine loads the image(s) and sets them in the pages internally. The original image reference can be obtained from the page using IOcrPage.GetRasterImage(ocrpagetype.original). Sharing the original image minimizes the memory used during OCR operations.

This member only works with memory-based documents and will throw an exception otherwise. For more information, refer to IOcrDocumentManager.CreateDocument and Programming with the LEADTOOLS .NET OCR.

Example

This example will add a raster image stored in an HTTP location to an OCR document

C#
VB
using Leadtools; 
using Leadtools.Codecs; 
using Leadtools.Ocr; 
using Leadtools.Document.Writer; 
using Leadtools.Forms.Common; 
using Leadtools.ImageProcessing.Core; 
 
public void AddPageFromDibExample() 
{ 
   string tifFileName = Path.Combine(LEAD_VARS.ImagesDir, "Ocr1.tif"); 
   string bmpFileName = Path.Combine(LEAD_VARS.ImagesDir, "Ocr1.bmp"); 
   string pdfFileName = Path.Combine(LEAD_VARS.ImagesDir, "Ocr1.pdf"); 
 
   // Get a DIB 
   // In this example, we will save the TIF file as BMP, then load it without the BITMAPFILEHEADER structure 
   // The result is a valid Windows DIB 
 
   using (RasterCodecs codecs = new RasterCodecs()) 
      codecs.Convert(tifFileName, bmpFileName, RasterImageFormat.Bmp, 0, 0, 1, null); 
 
 
   // From MSDN 
   const int bitmapFileHeaderStructSize = 14; 
   IntPtr dib = IntPtr.Zero; 
 
   using (FileStream fs = File.OpenRead(bmpFileName)) 
   { 
      // Allocate the DIB 
      int dibSize = (int)fs.Length - bitmapFileHeaderStructSize; 
      dib = Marshal.AllocHGlobal(dibSize); 
      int dibOffset = 0; 
 
      // Now read it 
      fs.Seek(bitmapFileHeaderStructSize, SeekOrigin.Begin); 
 
      const int bufferSize = 1024 * 4; 
      byte[] buffer = new byte[bufferSize]; 
      int bytes = 0; 
      do 
      { 
         bytes = fs.Read(buffer, 0, bufferSize); 
         if (bytes > 0) 
         { 
            IntPtr dibPtr = new IntPtr(dib.ToInt64() + dibOffset); 
            Marshal.Copy(buffer, 0, dibPtr, bytes); 
            dibOffset += bytes; 
         } 
      } 
      while (bytes > 0); 
   } 
 
   // 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 the image 
         ocrDocument.Pages.AddDib(dib, null); 
 
         // Free the DIB since we do not need it anymore 
         Marshal.FreeHGlobal(dib); 
 
         // 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(); 
   } 
} 
 
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.Document.Writer 
Imports Leadtools.Forms 
Imports Leadtools.ImageProcessing.Core 
 
Public Sub AddPageFromDibExample() 
   Dim tifFileName As String = Path.Combine(LEAD_VARS.ImagesDir, "Ocr1.tif") 
   Dim bmpFileName As String = Path.Combine(LEAD_VARS.ImagesDir, "Ocr1.bmp") 
   Dim pdfFileName As String = Path.Combine(LEAD_VARS.ImagesDir, "Ocr1.pdf") 
 
   ' Get a DIB 
   ' In this example, we will save the TIF file as BMP, then load it without the BITMAPFILEHEADER structure 
   ' The result is a valid Windows DIB 
 
   Using codecs As New RasterCodecs() 
      codecs.Convert(tifFileName, bmpFileName, RasterImageFormat.Bmp, 0, 0, 1, 
       Nothing) 
   End Using 
 
 
   ' From MSDN 
   Const bitmapFileHeaderStructSize As Integer = 14 
   Dim dib As IntPtr = IntPtr.Zero 
 
   Using fs As FileStream = File.OpenRead(bmpFileName) 
      ' Allocate the DIB 
      Dim dibSize As Integer = CInt(fs.Length) - bitmapFileHeaderStructSize 
      dib = Marshal.AllocHGlobal(dibSize) 
      Dim dibOffset As Integer = 0 
 
      ' Now read it 
      fs.Seek(bitmapFileHeaderStructSize, SeekOrigin.Begin) 
 
      Const bufferSize As Integer = 1024 * 4 
      Dim buffer As Byte() = New Byte(bufferSize - 1) {} 
      Dim bytes As Integer = 0 
      Do 
         bytes = fs.Read(buffer, 0, bufferSize) 
         If bytes > 0 Then 
            Dim dibPtr As New IntPtr(dib.ToInt64() + dibOffset) 
            Marshal.Copy(buffer, 0, dibPtr, bytes) 
            dibOffset += bytes 
         End If 
      Loop While bytes > 0 
   End Using 
 
   ' 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 the image 
         ocrDocument.Pages.AddDib(dib, Nothing) 
 
         ' Free the DIB since we do not need it anymore 
         Marshal.FreeHGlobal(dib) 
 
         ' 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 
 
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 

Requirements

Target Platforms

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Leadtools.Ocr Assembly