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LocalHistogramEqualizeCommand Class
See Also  Members   Example 



Linearizes the number of pixels locally in an image, based on a specific color space. This can be used to bring out the detail in dark areas of an image, and smooth the edges between blocks. This class is available in the Medical Toolkits.

Syntax

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

Example

Run the LocalHistogramEqualizeCommand on an image.

Visual BasicCopy Code
Public Sub LocalHistogramEqualizeCommandExample()
   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 LocalHistogramEqualizeCommand = New LocalHistogramEqualizeCommand
   command.Width = 15
   command.Height = 15
   command.WidthExtension = 100
   command.HeightExtension = 100
   command.Smooth = 0
   command.Type = HistogramEqualizeType.Yuv
   ' Local Histogram equalize the image.
   command.Run(leadImage)
   codecs.Save(leadImage, LeadtoolsExamples.Common.ImagesPath.Path + "Result.jpg", RasterImageFormat.Jpeg, 24)

   RasterCodecs.Shutdown()
End Sub
C#Copy Code
public void LocalHistogramEqualizeCommandExample() 
{ 
   // 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 
   LocalHistogramEqualizeCommand command = new LocalHistogramEqualizeCommand(); 
   command.Width           = 15; 
   command.Height          = 15; 
   command.WidthExtension  = 100; 
   command.HeightExtension = 100; 
   command.Smooth          = 0; 
   command.Type            = HistogramEqualizeType.Yuv; 
   // Local Histogram equalize the image. 
   command.Run(image); 
   codecs.Save(image, LeadtoolsExamples.Common.ImagesPath.Path + "Result.jpg", RasterImageFormat.Jpeg, 24); 
 
   RasterCodecs.Shutdown(); 
}

Remarks

  • This class applies the histogram equalizer locally on the image. The image is divided into local rectangles of dimension (Width, Height). The number of pixels inside each local rectangle are linearized according the histogram calculated for an extended rectangle around each local rectangle. The extended rectangles are of dimension:
    ((Width+2 * WidthExtension) , ( Height + 2 * HeightExtension)).

    For an example, see the following drawing:

    A rectangle and its associated extension, where the histogram is calculated.
  • Use this class to bring out details in an image that has portions that are too dark or too bright. An example of this is a picture taken with a flashlight in a dark room. In such a picture, the subject receives good light while the background is very dark. The application of the local histogram brings out details, but creates a blocky artifact. Use Smooth to reduce the blockiness of the result.
  • 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.LocalHistogramEqualizeCommand

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