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Java example source code file (PolygonChromosome.java)

This example Java source code file (PolygonChromosome.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

abstractlistchromosome, arraylist, awt, bufferedimage, graphics2d, image, invalidrepresentationexception, list, override, polygonchromosome, string, util

The PolygonChromosome.java Java example source code

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.math3.userguide.genetics;

import java.awt.AlphaComposite;
import java.awt.Color;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.image.BufferedImage;
import java.util.ArrayList;
import java.util.List;

import org.apache.commons.math3.genetics.AbstractListChromosome;
import org.apache.commons.math3.genetics.Chromosome;
import org.apache.commons.math3.genetics.InvalidRepresentationException;

/**
 * A simple chromosome representing a list of polygons.
 */
public class PolygonChromosome extends AbstractListChromosome<Polygon> {

    /** The reference image for fitness testing. */
    private static BufferedImage refImage;
    /** The image buffer used to draw the current chromosome during fitness testing. */
    private static BufferedImage testImage;

    public static void setRefImage(BufferedImage ref) {
        refImage = ref;
    }

    public static void setTestImage(BufferedImage image) {
        testImage = image;
    }

    public PolygonChromosome(List<Polygon> representation) {
        super(representation);
    }

    @Override
    protected void checkValidity(List<Polygon> chromosomeRepresentation) throws InvalidRepresentationException {
        // do nothing
    }

    @Override
    public AbstractListChromosome<Polygon> newFixedLengthChromosome(List chromosomeRepresentation) {
        return new PolygonChromosome(chromosomeRepresentation);
    }

    /**
     * Return the internal representation, which is needed for our custom mutation policy.
     *
     * @return the list of polygons
     */
    public List<Polygon> getPolygonRepresentation() {
        return getRepresentation();
    }

    /**
     * Calculate the fitness function for this chromosome.
     * <p>
     * For this purpose, we first draw the polygons on the test buffer, and
     * then compare the resulting image pixel by pixel with the reference image.
     */
    public double fitness() {

        Graphics2D g2 = testImage.createGraphics();
        
        int width = testImage.getWidth();
        int height = testImage.getHeight();

        draw(g2, width, height);
        g2.dispose();

        int[] refPixels = refImage.getData().getPixels(0, 0, refImage.getWidth(), refImage.getHeight(), (int[]) null);
        int[] testPixels = testImage.getData().getPixels(0, 0, testImage.getWidth(), testImage.getHeight(), (int[]) null);

        int diff = 0;
        int p = width * height * 4 - 1; // 4 channels: rgba
        int idx = 0;

        do {
            if (idx++ % 4 != 0) { // ignore the alpha channel for fitness
                int dp = testPixels[p] - refPixels[p];
                if (dp < 0) {
                    diff -= dp;
                } else {
                    diff += dp;
                }
            }
        } while(--p > 0);

        return (1.0 - diff / (width * height * 3.0 * 256));
    }

    public void draw(Graphics2D g, int width, int height) {
        g.setBackground(Color.WHITE);
        g.clearRect(0, 0, width, height);

        g.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        g.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER));

        List<Polygon> polygons = getPolygonRepresentation();
        for (Polygon p : polygons) {
            p.draw(g, width, height);
        }
    }

    @Override
    public String toString() {
        return String.format("(f=%s)", getFitness());
    }
    
    public static Chromosome randomChromosome(int polygonLength, int polygonCount) {
        List<Polygon> list = new ArrayList(polygonCount);
        for (int j = 0; j < polygonCount; j++) {
            list.add(Polygon.randomPolygon(polygonLength));
        }
        return new PolygonChromosome(list);
    }

}

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