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Java example source code file (Polygon.java)

This example Java source code file (Polygon.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

awt, color, generalpath, geometry, polygon, randomgenerator

The Polygon.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.Color;
import java.awt.Graphics2D;
import java.awt.geom.GeneralPath;

import org.apache.commons.math3.genetics.GeneticAlgorithm;
import org.apache.commons.math3.random.RandomGenerator;
import org.apache.commons.math3.util.FastMath;

/**
 * Represents a fixed size polgon with its fill color.
 */
public class Polygon {

    // the polygon in packed representation:
    // index | data
    //    0  | red component
    //    1  | green component
    //    2  | blue component
    //    3  | alpha channel
    //    4  | first x coordinate
    //    5  | first y coordinate
    //    6  | second x coordinate
    //  ...
    //    N  | last y coordinate
    // ---------------------------
    /// size = 4 + 2*polygonlength
    private float[] data;

    /**
     * Creates a new random Polygon of the given length.
     */
    public static Polygon randomPolygon(int length) {
        final int polygonSize = 4 + 2 * length;

        final RandomGenerator random = GeneticAlgorithm.getRandomGenerator();
        
        Polygon p = new Polygon();
        p.data = new float[polygonSize];

        p.data[0] = random.nextFloat(); // r
        p.data[1] = random.nextFloat(); // g
        p.data[2] = random.nextFloat(); // b
        p.data[3] = FastMath.max(0.2f, random.nextFloat() * random.nextFloat()); // a
        
        float px = random.nextFloat();
        float py = random.nextFloat();
        
        for (int k = 0; k < length; k++) {
            p.data[4 + 2*k] = px + (random.nextFloat() - 0.5f);
            p.data[5 + 2*k] = py + (random.nextFloat() - 0.5f);
        }
        return p;
    }

    /**
     * Return a new Polygon, mutated with the given rate and amount.
     * <p>
     * Each component of the Polygon may be mutated according to the specified mutation rate.
     * In case a component is going to be mutated, its value will be randomly modified in the
     * uniform range of [-mutationAmount, +mutationAmount].
     * 
     * @param mutationRate the mutation rate
     * @param mutationAmount the mutation amount
     * @return a new Polygon
     */
    public Polygon mutate(float mutationRate, float mutationAmount) {
        Polygon mutated = new Polygon();
        int size = data.length;
        mutated.data = new float[size];
        for (int i = 0; i < size; i++) {
            float val = this.data[i];
            if (GeneticAlgorithm.getRandomGenerator().nextFloat() < mutationRate) {
                val += GeneticAlgorithm.getRandomGenerator().nextFloat() * mutationAmount * 2 - mutationAmount;
                
                if (val < 0f) {
                    val = 0f;
                } else if (val > 1f) {
                    val = 1f;
                }
            }
            mutated.data[i] = val;
        }
        return mutated;
    }    

    /**
     * Draw the Polygon to the buffer of the given size.
     */
    public void draw(Graphics2D g, int width, int height) {
        g.setColor(new Color(data[0], data[1], data[2], data[3]));

        GeneralPath path = new GeneralPath();
        path.moveTo(data[4] * width, data[5] * height);
        
        int polygonLength = (data.length - 4) / 2;
        for (int j = 1; j < polygonLength; j++) {
            path.lineTo(data[4 + j * 2] * width, data[5 + j * 2] * height);
        }
        path.closePath();

        g.fill(path);
    }
}

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