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HistogramEqualizeCommand Class
See Also  Members   Example 



Linearizes the number of pixels, in an image, based on the specified color space. This can be used to bring out the detail in dark areas of an image. This function is useful for pre-processing images for the purpose of improving barcode recognition results.

Syntax

Visual Basic (Declaration) 
Public Class HistogramEqualizeCommand 
   Inherits RasterCommand
   Implements IRasterCommand 
Visual Basic (Usage)Copy Code
Dim instance As HistogramEqualizeCommand
C# 
public class HistogramEqualizeCommand : RasterCommand, IRasterCommand 
C++/CLI 
public ref class HistogramEqualizeCommand : public RasterCommand, IRasterCommand 

Example

Run the HistogramEqualizeCommand on an image and apply histogram equalization with YUV color space.

Visual BasicCopy Code
Public Sub HistogramEqualizeCommandExample()
   RasterCodecs.Startup()
   Dim codecs As New RasterCodecs()
   codecs.ThrowExceptionsOnInvalidImages = True

   Dim leadImage As RasterImage = codecs.Load(LeadtoolsExamples.Common.ImagesPath.Path + "Master.jpg")

   ' Prepare the command
   Dim command As HistogramEqualizeCommand = New HistogramEqualizeCommand
   'Histogram equalize the image.
   command.Type = HistogramEqualizeType.Yuv

   command.Run(leadImage)
   codecs.Save(leadImage, LeadtoolsExamples.Common.ImagesPath.Path + "Result.jpg", RasterImageFormat.Jpeg, 24)

   RasterCodecs.Shutdown()
End Sub
C#Copy Code
public void HistogramEqualizeCommandExample() 
{ 
   // Load an image 
   RasterCodecs.Startup(); 
   RasterCodecs codecs = new RasterCodecs(); 
   codecs.ThrowExceptionsOnInvalidImages = true; 
 
   RasterImage image = codecs.Load(LeadtoolsExamples.Common.ImagesPath.Path + "Master.jpg"); 
 
   // Prepare the command 
   HistogramEqualizeCommand command = new HistogramEqualizeCommand(); 
   //Histogram equalize the image. 
   command.Type   = HistogramEqualizeType.Yuv; 
   command.Run(image); 
   codecs.Save(image, LeadtoolsExamples.Common.ImagesPath.Path + "Result.jpg", RasterImageFormat.Jpeg, 24); 
 
   RasterCodecs.Shutdown(); 
}

Remarks

  • Previously this class only equalized the number of pixels per gray level, using a gray level representation of the image. This functionality is now obtained by passing HistogramEqualizeType.Gray for the Type property.
  • For the best results, set Type to HistogramEqualizeType.Yuv
  • This class can process the whole image or a region of the image.
  • This class supports 12 and 16-bit grayscale and 48 and 64-bit color images. Support for 12 and 16-bit grayscale and 48 and 64-bit color images is available only in the Document/Medical toolkits.
  • This command does not support 32-bit grayscale images.
For more information, refer to Changing Brightness and Contrast.

Inheritance Hierarchy

System.Object
   Leadtools.ImageProcessing.RasterCommand
      Leadtools.ImageProcessing.Color.HistogramEqualizeCommand

Requirements

Target Platforms: Microsoft .NET Framework 2.0, Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family

See Also