HistogramContrastCommand Class

Summary

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

Syntax

Objective-C

C++/CLI

Java

Python

public class HistogramContrastCommand : RasterCommand

@interface LTHistogramContrastCommand : LTRasterCommand

public class HistogramContrastCommand 
    extends RasterCommand

public ref class HistogramContrastCommand : public RasterCommand

class HistogramContrastCommand(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;

Histogram Contrast Function - Before

Histogram Contrast Function - After

View additional platform support for this Histogram Contrast function.

Example

Run the HistogramContrastCommand on an image and increase its contrast.

Java

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:\LEADTOOLS23\Resources\Images"; 
}

 
import java.io.File; 
import java.io.IOException; 
 
import org.junit.*; 
import org.junit.runner.JUnitCore; 
import org.junit.runner.Result; 
import org.junit.runner.notification.Failure; 
import static org.junit.Assert.*; 
 
import leadtools.*; 
import leadtools.codecs.*; 
import leadtools.imageprocessing.color.*; 
 
 
public void histogramContrastCommandExample() { 
 
   final String LEAD_VARS_IMAGES_DIR = "C:\\LEADTOOLS23\\Resources\\Images"; 
 
   // Load an image 
   RasterCodecs codecs = new RasterCodecs(); 
   codecs.setThrowExceptionsOnInvalidImages(true); 
   String srcFileName = combine(LEAD_VARS_IMAGES_DIR, "IMAGE1.CMP"); 
   RasterImage image = codecs.load(srcFileName); 
   System.out.println("Image loaded from: \n" + srcFileName); 
   // Prepare the command 
   HistogramContrastCommand command = new HistogramContrastCommand(); 
   // Increase the contrast using the histogram by 25 percent of the possible 
   // range. 
   command.setContrast(250); 
   // Change the contrast of the image 
   command.run(image); 
   codecs.save(image, combine(LEAD_VARS_IMAGES_DIR, "Result.jpg"), RasterImageFormat.JPEG, 24); 
 
   System.out.println("Command run and image saved to " + combine(LEAD_VARS_IMAGES_DIR, "result.jpg")); 
   assertTrue(new File(combine(LEAD_VARS_IMAGES_DIR, "result.jpg")).exists()); 
 
}