Convex hull example for user guide.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/math/trunk@1563008 13f79535-47bb-0310-9956-ffa450edef68

src/userguide/java/org/apache/commons/math3/userguide/geometry/ConvexHullExample.java

@@ -0,0 +1,134 @@
+package org.apache.commons.math3.userguide.geometry;
+
+import java.awt.Color;
+import java.awt.Dimension;
+import java.awt.FlowLayout;
+import java.awt.Graphics;
+import java.awt.Graphics2D;
+import java.awt.RenderingHints;
+import java.awt.geom.Line2D;
+import java.awt.geom.Rectangle2D;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+
+import javax.swing.JComponent;
+
+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.GrahamScan2D;
+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;
+
+/**
+ * Plots 2D samples drawn from various pseudo / quasi-random generators.
+ */
+public class ConvexHullExample {
+
+    public static List<Vector2D> createRandomPoints(int size) {
+        RandomGenerator random = new MersenneTwister(10);
+
+        // create the cloud container
+        List<Vector2D> points = new ArrayList<Vector2D>(size);
+        // fill the cloud with a random distribution of points
+        for (int i = 0; i < size; i++) {
+            points.add(new Vector2D(random.nextDouble() * 2.0 - 1.0, random.nextDouble() * 2.0 - 1.0));
+        }
+        return points;
+    }
+
+    @SuppressWarnings("serial")
+    public static class Display extends ExampleFrame {
+        
+        public Display() {
+            setTitle("Commons-Math: Convex Hull examples");
+            setSize(400, 400);
+            
+            setLayout(new FlowLayout());
+            
+            GrahamScan2D generator = new GrahamScan2D();
+            Collection<Vector2D> cloud = createRandomPoints(150);
+            ConvexHull2D hull = generator.generate(cloud);
+
+            add(new Plot(cloud, hull));
+        }
+    }
+
+    @SuppressWarnings("serial")
+    public static class Plot extends JComponent {
+
+        private static double PAD = 10;
+
+        private Iterable<Vector2D> cloud;
+        private ConvexHull2D hull;
+
+        public Plot(Iterable<Vector2D> cloud, ConvexHull2D hull) {
+            this.cloud = cloud;
+            this.hull = hull;
+        }
+        
+        @Override
+        protected void paintComponent(Graphics g) {
+            super.paintComponent(g);
+            Graphics2D g2 = (Graphics2D)g;
+            g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
+                                RenderingHints.VALUE_ANTIALIAS_ON);
+
+            int w = getWidth();
+            int h = getHeight();
+
+            g2.clearRect(0, 0, w, h);
+            
+            g2.setPaint(Color.black);
+            g2.drawRect(0, 0, w - 1, h - 1);
+            
+            for (Vector2D point : cloud) {
+                drawPoint(g2, point, w, h);
+            }
+            
+            g.setColor(Color.RED);
+            Vector2D firstPoint = hull.getVertices()[0];
+            Vector2D lastPoint = null;
+            for (Vector2D point : hull.getVertices()) {
+                drawPoint(g2, point, w, h);
+                if (lastPoint != null) {
+                    drawLine(g2, lastPoint, point, w, h);
+                }
+                lastPoint = point;
+            }
+
+            drawLine(g2, lastPoint, firstPoint, w, h);
+        }        
+
+        private void drawPoint(Graphics2D g2, Vector2D point, int width, int height) {
+            Vector2D p = transform(point, width, height);
+            double[] arr = p.toArray();
+            g2.draw(new Rectangle2D.Double(arr[0] - 1, arr[1] - 1, 2, 2));
+        }
+
+        public void drawLine(Graphics2D g2, Vector2D point1, Vector2D point2, int width, int height) {
+            Vector2D p1 = transform(point1, width, height);
+            double[] arr1 = p1.toArray();
+            Vector2D p2 = transform(point2, width, height);
+            double[] arr2 = p2.toArray();            
+            g2.draw(new Line2D.Double(arr1[0], arr1[1], arr2[0], arr2[1]));
+        }
+
+        @Override
+        public Dimension getPreferredSize() {
+            return new Dimension(300, 300);
+        }
+
+        private Vector2D transform(Vector2D point, int width, int height) {
+            double[] arr = point.toArray();
+            return new Vector2D(new double[] { PAD + (arr[0] + 1) / 2.0 * (width - 2 * PAD),
+                                               height - PAD - (arr[1] + 1) / 2.0 * (height - 2 * PAD) });
+        }
+    }
+
+    public static void main(String[] args) {
+        ExampleUtils.showExampleFrame(new Display());
+    }
+}