How to Make a Histogram in Java

A histogram is a graphical or numerical representation of the number of pixels and lines of color found in an image. Some high-end digital cameras will display this information for you in their settings, but to get the histograms of images you have on your computer, you will need to code a simple Java program.

Difficulty: Moderate

Instructions

Things You'll Need:

• Java Advanced Imaging API

1. Open the Java program and start a new project.

2. Use the "PlanarImage" and "Create" functions to load an image on your hard drive into the new program's memory. Write out the code so the first line of the program reads something like "PlanarImage picturename JAI.create("fileload",picturename.Getabsolutepath())"

3. Make a new array using double integers ranging from zero to 256. Define both the low end of the array and the high end of the array using brackets and a semicolon, just as you would when making any other array.

4. Add the image into the array, then count through the lines of color in the image using the ".add" command.

5. Use the "GetProperty" feature to produce a Histogram of the image. The code should read "op.Getproperty("histogram")"

6. Execute the program to finish making the histogram.

Tips & Warnings

• You can display the histogram information in an easy-to-read chart by passing the information in the array as a string by using the "GraphIt" feature of the "Chart" function.

Resources

• Official Java Website
• Java Advanced Imaging API

[sergei175]

on 11/1/2009
You can use the jHepWork Java libraries,
see http://jwork.org/jhepwork/

The classes are H1D, H2D, H3D.
This is an example:

import java.awt.Color;
import java.util.Random;
import jhplot.*;

class histo1
{

public static void main(String[] args)
{


HPlot c1 = new HPlot("Canvas",600,400,1,1);
c1.setGTitle("Global title for F_{2} and x_{γ} ");
c1.visible(true);
c1.setAutoRange();


H1D h1 = new H1D("Simple1",20, -2.0, 2.0);
Random rand = new Random();
for (int i=0; i<100; i++) h1.fill(rand.nextGaussian());


c1.draw(h1);
h1.setColor(Color.blue);
h1.setPenWidthErr(2);
c1.setNameX("Xaxis");
c1.setNameY("Yaxis");
c1.setName("Canvas title");
c1.drawStatBox(h1);
c1.update();

// make png figure
c1.export("test.png");

}


}
~