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.

Object Model

Syntax

Visual Basic
C#
WinRT C#
WinRT JavaScript
C++

public class LocalHistogramEqualizeCommand : Leadtools.ImageProcessing.RasterCommand, Leadtools.ImageProcessing.IRasterCommand

'Declaration
 
Public Class LocalHistogramEqualizeCommand 
   Inherits Leadtools.ImageProcessing.RasterCommand
   Implements Leadtools.ImageProcessing.IRasterCommand

'Usage
 
Dim instance As LocalHistogramEqualizeCommand

public sealed class LocalHistogramEqualizeCommand : Leadtools.ImageProcessing.IRasterCommand

function Leadtools.ImageProcessing.Color.LocalHistogramEqualizeCommand()

public ref class LocalHistogramEqualizeCommand : public Leadtools.ImageProcessing.RasterCommand, Leadtools.ImageProcessing.IRasterCommand

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.

Example

Visual Basic
C#
WinRT C#
WinRT JavaScript
Silverlight C#
Silverlight VB

Public Sub LocalHistogramEqualizeCommandExample()
   Dim codecs As New RasterCodecs()
   codecs.ThrowExceptionsOnInvalidImages = True

   Dim leadImage As RasterImage = codecs.Load(Path.Combine(LEAD_VARS.ImagesDir, "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, Path.Combine(LEAD_VARS.ImagesDir, "Result.jpg"), RasterImageFormat.Jpeg, 24)

End Sub

Public NotInheritable Class LEAD_VARS
   Public Const ImagesDir As String = "C:\Users\Public\Documents\LEADTOOLS Images"
End Class

public void LocalHistogramEqualizeCommandExample()
   {
      // Load an image
      RasterCodecs codecs = new RasterCodecs();
      codecs.ThrowExceptionsOnInvalidImages = true;

      RasterImage image = codecs.Load(Path.Combine(LEAD_VARS.ImagesDir, "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, Path.Combine(LEAD_VARS.ImagesDir, "Result.jpg"), RasterImageFormat.Jpeg, 24);

   }

static class LEAD_VARS
{
   public const string ImagesDir = @"C:\Users\Public\Documents\LEADTOOLS Images";
}

[TestMethod]
public async Task LocalHistogramEqualizeCommandExample()
{
   // Load an image
   RasterCodecs codecs = new RasterCodecs();
   codecs.ThrowExceptionsOnInvalidImages = true;
   // Load the image
   string srcFileName = @"Assets\Image1.cmp";
   StorageFile loadFile = await Tools.AppInstallFolder.GetFileAsync(srcFileName);
   RasterImage image = await codecs.LoadAsync(LeadStreamFactory.Create(loadFile));

   // 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);

   string destFileName = @"result.jpg";
   StorageFile saveFile = await Tools.AppLocalFolder.CreateFileAsync(destFileName);
   await codecs.SaveAsync(image, LeadStreamFactory.Create(saveFile), RasterImageFormat.Jpeg, 0);
}

public void LocalHistogramEqualizeCommandExample(RasterImage image, Stream outStream)
{
   // 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);
   // Save result image
   RasterCodecs codecs = new RasterCodecs();
   codecs.Save(image, outStream, RasterImageFormat.Jpeg, 24);
   image.Dispose();
}

Public Sub LocalHistogramEqualizeCommandExample(ByVal image As RasterImage, ByVal outStream As Stream)
   ' 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(image)
   ' Save result image
   Dim codecs As RasterCodecs = New RasterCodecs()
   codecs.Save(image, outStream, RasterImageFormat.Jpeg, 24)
   image.Dispose()
End Sub

Requirements

Target Platforms: Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

Reference

LocalHistogramEqualizeCommand Members
Leadtools.ImageProcessing.Color Namespace
Changing Brightness and Contrast
ChangeIntensityCommand Class
GammaCorrectCommand Class
ChangeContrastCommand Class
HistogramContrastCommand Class
StretchIntensityCommand Class
RemapIntensityCommand Class
InvertCommand Class
ChangeHueCommand Class
ChangeSaturationCommand Class
Leadtools.ImageProcessing.FillCommand
HistogramCommand Class
Leadtools.ImageProcessing.Core.WindowLevelCommand
AutoColorLevelCommand Class
ColorLevelCommand Class
Leadtools.ImageProcessing.Core.CorrelationListCommand
GrayScaleToDuotoneCommand Class
GrayScaleToMultitoneCommand Class
Leadtools.ImageProcessing.Core.HolePunchRemoveCommand
SelectiveColorCommand Class
Leadtools.ImageProcessing.Effects.SkeletonCommand