GetRasterImage(OcrPageType) Method

Summary

Gets the current or processing image data of this page as a raster image.

Syntax

Objective-C

C++/CLI

Java

Python

public RasterImage GetRasterImage( 
   OcrPageType pageType 
)

- (nullable LTRasterImage *)rasterImageForPageType:(LTOcrPageType)pageType error:(NSError **)error;

public RasterImage getRasterImage(OcrPageType pageType)

RasterImage^ GetRasterImage(  
   OcrPageType pageType 
)

def GetRasterImage(self,pageType):

Parameters

pageType
The page type to get.

Return Value

A RasterImage object that represent the current or processing image data of this page.

Remarks

Each IOcrPage contains two versions of the image used to create it: an original (current) and an optional processing version. The processing version usually black/white and has uniform resolution (if the original image is FAX for example) and it gets passed to the internal OCR engine during the zoning and recognition process. The AutoPreprocess method also uses the B/W image to determine if the page is inverted, skewed or has an orientation; however, it applies the correction to both the current and processing images.

You can use GetRasterImage(OcrPageType) to get a copy of either of these images.

You cannot set the processing image of a page; it is created automatically by the engine. This is why there is no IOcrPage.SetRasterImage(OcrPageType pageType) method.

If the original image is black and white and has uniform vertical and horizontal resolution, then the engine will not create a processing image, in other words, GetRasterImage(OcrPageType.Current) and GetRasterImage(OcrPageType.Processing) will return identical RasterImage objects.

If the original image has different horizontal and vertical resolution, such as a FAX image, the processing page will be have be resized to have uniform resolution.

The LEADTOOLS C# .NET Main OCR demo (<INSTALLDIR>\Examples\OCR\DotNet\OcrDemo) has an option in the page menu to toggle between showing the current (default) or processing image of each page.

Example

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 OcrPageTypeExample() 
{ 
   OcrEngineType engineType = OcrEngineType.LEAD; 
   using (IOcrEngine ocrEngine = OcrEngineManager.CreateEngine(engineType)) 
   { 
      ocrEngine.Startup(null, null, null, LEAD_VARS.OcrLEADRuntimeDir); 
 
      // Load an image as 24-bpp 
      RasterImage image = ocrEngine.RasterCodecsInstance.Load(Path.Combine(LEAD_VARS.ImagesDir, "Ocr1.tif"), 24, CodecsLoadByteOrder.Bgr, 1, 1); 
      // Show the original image properties 
      Console.WriteLine("Original size is {0} by {1} at {2} bits/pixel", image.ImageWidth, image.ImageHeight, image.BitsPerPixel); 
      System.Diagnostics.Debug.Assert(image.BitsPerPixel == 24); 
 
      // Create a page for it 
      using (IOcrPage ocrPage = ocrEngine.CreatePage(image, OcrImageSharingMode.AutoDispose)) 
      { 
         // Show the current OCR page size and color depth 
         using (image = ocrPage.GetRasterImage(OcrPageType.Current)) 
         { 
            Console.WriteLine("Original size is {0} by {1} at {2} bits/pixel", image.ImageWidth, image.ImageHeight, image.BitsPerPixel); 
            System.Diagnostics.Debug.Assert(image.BitsPerPixel == 24); 
         } 
 
         // Show the processing OCR page size and color depth 
         using (image = ocrPage.GetRasterImage(OcrPageType.Processing)) 
         { 
            Console.WriteLine("Original size is {0} by {1} at {2} bits/pixel", image.ImageWidth, image.ImageHeight, image.BitsPerPixel); 
            System.Diagnostics.Debug.Assert(image.BitsPerPixel == 1); 
         } 
      } 
   } 
} 
 
static class LEAD_VARS 
{ 
   public const string ImagesDir = @"C:\LEADTOOLS22\Resources\Images"; 
   public const string OcrLEADRuntimeDir = @"C:\LEADTOOLS22\Bin\Common\OcrLEADRuntime"; 
}