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LocalHistogramEqualizeCommand Class

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.
public class LocalHistogramEqualizeCommand : RasterCommand 
Public Class LocalHistogramEqualizeCommand  
   Inherits RasterCommand 
@interface LTLocalHistogramEqualizeCommand : LTRasterCommand 
public class LocalHistogramEqualizeCommand extends RasterCommand 
public ref class LocalHistogramEqualizeCommand : public RasterCommand   
  • 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.
  • This command supports signed/unsigned data images.

For more information, refer to Changing Brightness and Contrast.


Run the LocalHistogramEqualizeCommand on an image.

using Leadtools; 
using Leadtools.Codecs; 
using Leadtools.ImageProcessing.Color; 
public void LocalHistogramEqualizeCommandExample() 
   // Load an image 
   RasterCodecs codecs = new RasterCodecs(); 
   codecs.ThrowExceptionsOnInvalidImages = true; 
   RasterImage image = codecs.Load(Path.Combine(LEAD_VARS.ImagesDir, "IMAGE1.CMP")); 
   // 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. 
   codecs.Save(image, Path.Combine(LEAD_VARS.ImagesDir, "Result.jpg"), RasterImageFormat.Jpeg, 24); 
static class LEAD_VARS 
   public const string ImagesDir = @"C:\LEADTOOLS21\Resources\Images"; 
Imports Leadtools 
Imports Leadtools.Codecs 
Imports Leadtools.ImageProcessing.Color 
Public Sub LocalHistogramEqualizeCommandExample() 
   Dim codecs As New RasterCodecs() 
   codecs.ThrowExceptionsOnInvalidImages = True 
   Dim leadImage As RasterImage = codecs.Load(Path.Combine(LEAD_VARS.ImagesDir, "IMAGE1.CMP")) 
   ' 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. 
   codecs.Save(leadImage, Path.Combine(LEAD_VARS.ImagesDir, "Result.jpg"), RasterImageFormat.Jpeg, 24) 
End Sub 
Public NotInheritable Class LEAD_VARS 
   Public Const ImagesDir As String = "C:\LEADTOOLS21\Resources\Images" 
End Class 

Target Platforms

Help Version 21.0.2021.3.2
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Leadtools.ImageProcessing.Color Assembly