LocalHistogramEqualizeCommand Class

Summary

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.

Syntax

Objective-C

C++/CLI

Java

Python

public class LocalHistogramEqualizeCommand : RasterCommand

@interface LTLocalHistogramEqualizeCommand : LTRasterCommand

public class LocalHistogramEqualizeCommand 
    extends RasterCommand

public ref class LocalHistogramEqualizeCommand : public RasterCommand

class LocalHistogramEqualizeCommand(RasterCommand):

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.
This command supports signed/unsigned data images.

For more information, refer to Changing Brightness and Contrast.

Local Equalize Function - Before

Local Equalize Function - After

View additional platform support for this Local Equalize function.

Example

Run the LocalHistogramEqualizeCommand on an image.

Java

using Leadtools; 
using Leadtools.Codecs; 
using Leadtools.ImageProcessing.Color; 
 
 
public void LocalHistogramEqualizeCommandExample() 
{ 
   // Load an image 
   RasterCodecs codecs = new RasterCodecs(); 
   codecs.ThrowExceptionsOnInvalidImages = true; 
 
   RasterImage image = codecs.Load(Path.Combine(LEAD_VARS.ImagesDir, "IMAGE1.CMP")); 
 
   // 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:\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 localHistogramEqualizeCommandExample() { 
 
   final String LEAD_VARS_IMAGES_DIR = "C:\\LEADTOOLS23\\Resources\\Images"; 
 
   // Load an image 
   RasterCodecs codecs = new RasterCodecs(); 
   codecs.setThrowExceptionsOnInvalidImages(true); 
 
   RasterImage image = codecs.load(combine(LEAD_VARS_IMAGES_DIR, "IMAGE1.CMP")); 
 
   // Prepare the command 
   LocalHistogramEqualizeCommand command = new LocalHistogramEqualizeCommand(); 
   command.setWidth(15); 
   command.setHeight(15); 
   command.setWidthExtension(100); 
   command.setHeightExtension(100); 
   command.setSmooth(0); 
   command.setType(HistogramEqualizeType.YUV); 
   // Local Histogram equalize 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()); 
 
}

Requirements

Target Platforms

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Help Version 23.0.2024.3.3

Leadtools.ImageProcessing.Color Assembly

Introduction

Getting Started

Namespaces

Leadtools.ImageProcessing.Color Namespace

Assemblies

LocalHistogramEqualizeCommand Class

Reference