HistogramContrastCommand Class

Summary

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

Syntax

Objective-C

C++

Java

public class HistogramContrastCommand : RasterCommand

Public Class HistogramContrastCommand  
   Inherits RasterCommand

@interface LTHistogramContrastCommand : LTRasterCommand

public class HistogramContrastCommand extends RasterCommand

public ref class HistogramContrastCommand : public RasterCommand

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;

Example

Run the HistogramContrastCommand on an image and increase its contrast.

using Leadtools; 
using Leadtools.Codecs; 
using Leadtools.ImageProcessing.Color; 
 
public void HistogramContrastCommandExample() 
{ 
   // Load an image 
   RasterCodecs codecs = new RasterCodecs(); 
   codecs.ThrowExceptionsOnInvalidImages = true; 
 
   RasterImage image = codecs.Load(Path.Combine(LEAD_VARS.ImagesDir, "IMAGE1.CMP")); 
 
   // 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, 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 HistogramContrastCommandExample() 
   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 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, 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