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HistogramContrastCommand Class
See Also  Members   Example 



Increases or decreases the contrast of the image, using a histogram to determine the median brightness.

Syntax

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

Example

Run the HistogramContrastCommand on an image and increase its contrast.

Visual BasicCopy Code
Public Sub HistogramContrastCommandExample()
   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 HistogramContrastCommand = New HistogramContrastCommand
   'Increase the contrast using the histogram by 25 percent of the possible range.
   command.Contrast = 250

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

   RasterCodecs.Shutdown()
End Sub
C#Copy Code
public void HistogramContrastCommandExample() 
{ 
   // 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 
   HistogramContrastCommand command = new HistogramContrastCommand(); 
   //Increase the contrast using the histogram by 25 percent of the possible range. 
   command.Contrast = 250; 
   command.Run(image); 
   codecs.Save(image, LeadtoolsExamples.Common.ImagesPath.Path + "Result.jpg", RasterImageFormat.Jpeg, 24); 
 
   RasterCodecs.Shutdown(); 
}

Remarks

  • This class finds the median brightness of the image, then brightens the pixels with values above the median and darkens the pixels with values below the median. This is more sophisticated (but slower) than the ChangeContrastCommand, which uses the middle possible value (128) rather than finding the actual median.
  • 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.

If the image has a LUT and you want to work on the image data, set RasterImage.UseLookupTable to false. Then, after calling the method, reset the UselookupTable property to true, as follows: 


rasterImage.UseLookupTable = false;
Method(rasterImage);

rasterImage.UseLookupTable = true;

Inheritance Hierarchy

System.Object
   Leadtools.ImageProcessing.RasterCommand
      Leadtools.ImageProcessing.Color.HistogramContrastCommand

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