Geometry onjects,zoom in or out,how to design?

Question

I have plotted a composite geometry onject that has many polygons.
I want add one button event. Once I click it, the object will be zoom in or out,
What is the idea of it?
Thanks

Answer 1

import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.util.Hashtable;
import javax.swing.*;
import javax.swing.event.*;
public class CompositeZoom extends JPanel implements ChangeListener {
    GeneralPath path;
    double scale = 1.0;
    public void stateChanged(ChangeEvent e) {
        int value = ((JSlider)e.getSource()).getValue();
        scale = (value+4)/10.0;
        repaint();
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D)g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                            RenderingHints.VALUE_ANTIALIAS_ON);
        if(path == null) initPath();
        Rectangle r = path.getBounds();
        double x = r.getCenterX()*(1.0 - scale);
        double y = r.getCenterY()*(1.0 - scale);
        AffineTransform at = AffineTransform.getTranslateInstance(x, y);
        at.scale(scale, scale);
        g2.draw(at.createTransformedShape(path));
    private void initPath() {
        int cx = getWidth()/2;
        int cy = getHeight()/2;
        int d = 40;
        int R = Math.min(cx,cy)/3;
        int[][] xy = generateShapeArrays(cx-d, cy-d, R, 3);
        Polygon p = new Polygon(xy[0], xy[1], 3);
        path = new GeneralPath(p);
        xy = generateShapeArrays(cx+d, cy-d, R, 5);
        p = new Polygon(xy[0], xy[1], 5);
        path.append(p, false);
        xy = generateShapeArrays(cx-d, cy+d, R, 7);
        p = new Polygon(xy[0], xy[1], 7);
        path.append(p, false);
        xy = generateShapeArrays(cx+d, cy+d, R, 6);
        p = new Polygon(xy[0], xy[1], 6);
        path.append(p, false);
    private int[][] generateShapeArrays(int cx, int cy, int R, int sides) {
        int radInc = 0;
        if(sides % 2 == 0)
            radInc = 1;
        int[] x = new int[sides];
        int[] y = new int[sides];
        for(int i = 0; i < sides; i++) {
            x[i] = cx + (int)(R * Math.sin(radInc*Math.PI/sides));
            y[i] = cy - (int)(R * Math.cos(radInc*Math.PI/sides));
            radInc += 2;
        // keep base of triangle level
        if(sides == 3)
            y[2] = y[1];
        return new int[][] { x, y };
    private JSlider getControl() {
        int min = 1, max = 16, inc = 5;
        JSlider slider = new JSlider(min, max, 6);
        slider.setMajorTickSpacing(5);
        slider.setMinorTickSpacing(1);
        slider.setSnapToTicks(true);
        slider.setPaintTicks(true);
        slider.setLabelTable(getLabelTable(min, max, inc));
        slider.setPaintLabels(true);
        slider.addChangeListener(this);
        return slider;
    private Hashtable getLabelTable(int min, int max, int inc) {
        Hashtable<Integer, JLabel> table = new Hashtable<Integer, JLabel>();
        for(int j = min; j <= max; j+=inc) {
            String s = String.format("%.1f", (j+4)/10.0);
            table.put(Integer.valueOf(j), new JLabel(s));
        return table;
    public static void main(String[] args) {
        CompositeZoom test = new CompositeZoom();
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().add(test);
        f.getContentPane().add(test.getControl(), "Last");
        f.setSize(400,400);
        f.setLocation(200,200);
        f.setVisible(true);
}