HistogramEqualizeCommand Class

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.

Object Model

Syntax

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

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

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

'Usage
 
Dim instance As HistogramEqualizeCommand

public sealed class HistogramEqualizeCommand : Leadtools.ImageProcessing.IRasterCommand

function Leadtools.ImageProcessing.Color.HistogramEqualizeCommand()

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

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.

Example

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

Public Sub HistogramEqualizeCommandExample()
   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 HistogramEqualizeCommand = New HistogramEqualizeCommand
   'Histogram equalize the image.
   command.Type = HistogramEqualizeType.Yuv

   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 HistogramEqualizeCommandExample()
   {
      // Load an image
      RasterCodecs codecs = new RasterCodecs();
      codecs.ThrowExceptionsOnInvalidImages = true;

      RasterImage image = codecs.Load(Path.Combine(LEAD_VARS.ImagesDir, "Master.jpg"));

      // Prepare the command
      HistogramEqualizeCommand command = new HistogramEqualizeCommand();
      //Histogram equalize the image.
      command.Type   = HistogramEqualizeType.Yuv;
      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 HistogramEqualizeCommandExample()
{
   // 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
   HistogramEqualizeCommand command = new HistogramEqualizeCommand();
   //Histogram equalize the image.
   command.Type   = HistogramEqualizeType.Yuv;
   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 HistogramEqualizeCommandExample(RasterImage image, Stream outStream)
{
   // Prepare the command
   HistogramEqualizeCommand command = new HistogramEqualizeCommand();
   //Histogram equalize the image.
   command.Type   = HistogramEqualizeType.Yuv;
   command.Run(image);
   // Save result image
   RasterCodecs codecs = new RasterCodecs();
   codecs.Save(image, outStream, RasterImageFormat.Jpeg, 24);
   image.Dispose();
}

Public Sub HistogramEqualizeCommandExample(ByVal image As RasterImage, ByVal outStream As Stream)
   ' Prepare the command
   Dim command As HistogramEqualizeCommand = New HistogramEqualizeCommand()
   'Histogram equalize the image.
   command.Type = HistogramEqualizeType.Yuv
   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