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Java example source code file (GeometryExample.java)

This example Java source code file (GeometryExample.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

actionlistener, arraylist, awt, display, event, geometry, gui, jbutton, jpanel, list, pcanvas, pinputevent, pmousewheelzoomeventhandler, pnode, ppath, ptext, string, swing, util, vector2d

The GeometryExample.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.geometry;

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Component;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.geom.Point2D;
import java.util.ArrayList;
import java.util.List;

import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JComponent;
import javax.swing.JPanel;
import javax.swing.JSplitPane;

import org.apache.commons.math3.geometry.enclosing.Encloser;
import org.apache.commons.math3.geometry.enclosing.EnclosingBall;
import org.apache.commons.math3.geometry.enclosing.WelzlEncloser;
import org.apache.commons.math3.geometry.euclidean.twod.DiskGenerator;
import org.apache.commons.math3.geometry.euclidean.twod.Euclidean2D;
import org.apache.commons.math3.geometry.euclidean.twod.Segment;
import org.apache.commons.math3.geometry.euclidean.twod.Vector2D;
import org.apache.commons.math3.geometry.euclidean.twod.hull.ConvexHull2D;
import org.apache.commons.math3.geometry.euclidean.twod.hull.ConvexHullGenerator2D;
import org.apache.commons.math3.geometry.euclidean.twod.hull.MonotoneChain;
import org.apache.commons.math3.random.MersenneTwister;
import org.apache.commons.math3.random.RandomGenerator;
import org.apache.commons.math3.userguide.ExampleUtils;
import org.apache.commons.math3.userguide.ExampleUtils.ExampleFrame;
import org.apache.commons.math3.util.FastMath;
import org.piccolo2d.PCamera;
import org.piccolo2d.PCanvas;
import org.piccolo2d.PNode;
import org.piccolo2d.event.PBasicInputEventHandler;
import org.piccolo2d.event.PInputEvent;
import org.piccolo2d.event.PMouseWheelZoomEventHandler;
import org.piccolo2d.nodes.PPath;
import org.piccolo2d.nodes.PText;

/**
 * Simple example illustrating some parts of the geometry package.
 * 
 * TODO: 
 *  - select tolerance level
 *  - allow editing of the point set
 */
public class GeometryExample {

    public static List<Vector2D> createRandomPoints(int size) {
        RandomGenerator random = new MersenneTwister();

        // create the cloud container
        List<Vector2D> points = new ArrayList(size);
        // fill the cloud with a random distribution of points
        for (int i = 0; i < size; i++) {
            points.add(new Vector2D(FastMath.round(random.nextDouble() * 400 + 100),
                    FastMath.round(random.nextDouble() * 400 + 100)));
        }
        
        return points;
    }

    public static List<Vector2D> createCircle(int samples) {
        List<Vector2D> points = new ArrayList();
        final Vector2D center = new Vector2D(300, 300);
        double range = 2.0 * FastMath.PI;
        double step = range / (samples + 1);
        for (double angle = 0; angle < range; angle += step) {
            Vector2D circle = new Vector2D(FastMath.cos(angle), FastMath.sin(angle));
            points.add(circle.scalarMultiply(200).add(center));
        }
        
        return points;
    }

    public static List<Vector2D> createCross() {
        List<Vector2D> points = new ArrayList();
        
        for (int i = 100; i < 500; i += 10) {
            points.add(new Vector2D(300, i));
            points.add(new Vector2D(i, 300));
        }

        return points;
    }

    public static PCanvas createCanvas() {
        final PCanvas canvas = new PCanvas();
        final PCamera camera = canvas.getCamera();
        
        final PText tooltipNode = new PText();
        tooltipNode.setPickable(false);
        camera.addChild(tooltipNode);

        camera.addInputEventListener(new PBasicInputEventHandler() {
            public void mouseMoved(final PInputEvent event) {
                updateToolTip(event);
            }

            public void mouseDragged(final PInputEvent event) {
                updateToolTip(event);
            }

            public void updateToolTip(final PInputEvent event) {
                final PNode n = event.getPickedNode();
                final Object object = (Object) n.getAttribute("tooltip");
                if (object != null) {
                    final String tooltipString = object.toString();
                    final Point2D p = event.getCanvasPosition();

                    event.getPath().canvasToLocal(p, camera);

                    tooltipNode.setText(tooltipString);
                    tooltipNode.setOffset(p.getX() + 8, p.getY() - 8);
                } else {
                    tooltipNode.setText(null);
                }
            }
        });

        // uninstall default zoom event handler
        canvas.removeInputEventListener(canvas.getZoomEventHandler());

        // install mouse wheel zoom event handler
        final PMouseWheelZoomEventHandler mouseWheelZoomEventHandler = new PMouseWheelZoomEventHandler();
        canvas.addInputEventListener(mouseWheelZoomEventHandler);

        return canvas;
    }

    @SuppressWarnings("serial")
    public static class Display extends ExampleFrame {

        private List<Vector2D> points;
        private PCanvas canvas;
        private JComponent container;
        private JComponent controlPanel;

        public Display() {
            setTitle("Commons Math: Geometry Examples");
            setSize(800, 700);

            container = new JPanel(new BorderLayout());
            canvas = createCanvas();
            container.add(canvas);
            container.setBorder(BorderFactory.createLineBorder(Color.black, 1));

            controlPanel = new JPanel();
            JButton random = new JButton("Randomize");
            controlPanel.add(random);

            random.addActionListener(new ActionListener() {

//                @Override
                public void actionPerformed(ActionEvent e) {
                    canvas.getLayer().removeAllChildren();
                    
                    points = createRandomPoints(1000);
                    paintConvexHull();
                }
            });

            JButton circle = new JButton("Circle");
            controlPanel.add(circle);

            circle.addActionListener(new ActionListener() {

//                @Override
                public void actionPerformed(ActionEvent e) {
                    canvas.getLayer().removeAllChildren();
                    
                    points = createCircle(100);
                    paintConvexHull();
                }
            });

            JButton cross = new JButton("Cross");
            controlPanel.add(cross);

            cross.addActionListener(new ActionListener() {

//                @Override
                public void actionPerformed(ActionEvent e) {
                    canvas.getLayer().removeAllChildren();
                    
                    points = createCross();
                    paintConvexHull();
                }
            });

            JSplitPane splitpane = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT, container, controlPanel);
            splitpane.setDividerLocation(600);

            add(splitpane);
            
            points = createRandomPoints(1000);
            paintConvexHull();
        }

        @Override
        public Component getMainPanel() {
            return container;
        }
        
        public void paintConvexHull() {
            PNode pointSet = new PNode();
            for (Vector2D point : points) {
                final PNode node = PPath.createEllipse(point.getX() - 1, point.getY() - 1, 2, 2);
                node.addAttribute("tooltip", point);
                node.setPaint(Color.gray);
                pointSet.addChild(node);
            }

            canvas.getLayer().addChild(pointSet);

            ConvexHullGenerator2D generator = new MonotoneChain(true, 1e-6);
            ConvexHull2D hull = generator.generate(points); //AklToussaintHeuristic.reducePoints(points));

            PNode hullNode = new PNode();
            for (Vector2D vertex : hull.getVertices()) {
                final PPath node = PPath.createEllipse(vertex.getX() - 1, vertex.getY() - 1, 2, 2);
                node.addAttribute("tooltip", vertex);
                node.setPaint(Color.red);
                node.setStrokePaint(Color.red);
                hullNode.addChild(node);
            }

            for (Segment line : hull.getLineSegments()) {
                final PPath node = PPath.createLine(line.getStart().getX(), line.getStart().getY(),
                                                    line.getEnd().getX(), line.getEnd().getY());
                node.setPickable(false);
                node.setPaint(Color.red);
                node.setStrokePaint(Color.red);
                hullNode.addChild(node);
            }

            canvas.getLayer().addChild(hullNode);

            Encloser<Euclidean2D, Vector2D> encloser =
                    new WelzlEncloser<Euclidean2D, Vector2D>(1e-10, new DiskGenerator());
            EnclosingBall<Euclidean2D, Vector2D> ball = encloser.enclose(points);

            final double radius = ball.getRadius();
            PPath ballCenter =
                    PPath.createEllipse(ball.getCenter().getX() - 1, ball.getCenter().getY() - 1, 2, 2);
            ballCenter.setStrokePaint(Color.blue);
            ballCenter.setPaint(Color.blue);
            canvas.getLayer().addChild(0, ballCenter);

            PPath ballNode =
                    PPath.createEllipse(ball.getCenter().getX() - radius, ball.getCenter().getY() - radius,
                                        radius * 2, radius * 2);
            ballNode.setTransparency(1.0f);
            ballNode.setStrokePaint(Color.blue);
            canvas.getLayer().addChild(0, ballNode);
        }
    }

    public static void main(final String[] argv) {
        ExampleUtils.showExampleFrame(new Display());
    }
}

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