Inscribing the image in the points connectd by lines

Question

i have a problem in drawing lines inscribing the image over array of points
my code is
public class CaptureConvex extends JPanel {
private BufferedImage image;
Rectangle rect;
Ellipse2D.Double circle;
Dimension size = new Dimension();
private ConvexHull process;
CaptureConvex(BufferedImage image,ConvexHull process)
this.image = image;
this.process = process;
rect = new Rectangle(image.getWidth(), image.getHeight());
protected void paintComponent(Graphics g) {
//super.paintComponent(g);
Graphics2D g2 = (Graphics2D)g;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
double cx = rect.getCenterX();
double cy = rect.getCenterY();
double radius = Point2D.distance(cx, cy, rect.x, rect.y);
int diameter = (int)(2*radius)+1;
size.setSize(diameter, diameter);
// Draw image centered.
rect.x = (size.width - rect.width)/2;
rect.y = (size.height - rect.height)/2;
System.out.println(size.width+"newradius"+size.height);
System.out.println(rect.x+"newradius"+rect.y);
g2.drawImage(image, rect.x,rect.y, null);
double rx[] = process.getRxValue();
double ry[] = process.getRyValue();
int nValue = process.getnValue();
/** here is the problem
for (short i= 0;i<nValue;i++)
          g2.draw(new Line2D.Double(rx[i]+27,ry[i]+27,rx[i+1]+27,ry[i+1]+27));
}

Answer 1

import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.awt.image.BufferedImage;
import java.io.*;
import java.util.*;
import java.util.List;
import javax.imageio.ImageIO;
import javax.swing.*;
public class ConvexClip extends JPanel implements ActionListener {
    BufferedImage image;
    Rectangle rect;
    Random seed = new Random();
    Path2D.Double convexHull;
    boolean clipImage = false;
    ConvexClip(BufferedImage image) {
        this.image = image;
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D)g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                            RenderingHints.VALUE_ANTIALIAS_ON);
        if(rect == null)
            initGeometry();
        // Center the image in this component.
        int w = getWidth();
        int h = getHeight();
        rect.x = (w - rect.width)/2;
        rect.y = (h - rect.height)/2;
        // Position the convexHull over the image.
        AffineTransform at =
            AffineTransform.getTranslateInstance(rect.x, rect.y);
        Shape centeredHull = at.createTransformedShape(convexHull);
        if(clipImage) {
            Shape oldClip = g2.getClip();
            g2.setClip(centeredHull);
            g2.drawImage(image, rect.x, rect.y, this);
            g2.setClip(oldClip);
            g2.setPaint(getBackground());
            g2.draw(centeredHull);
        } else {
            g2.drawImage(image, rect.x, rect.y, this);
            g2.setPaint(Color.red);
            g2.draw(centeredHull);
    private void initGeometry() {
        rect = new Rectangle(image.getWidth(), image.getHeight());
        // Make up some points within the bounds of rect
        // whose current origin is 0,0.
        int n = 5 + seed.nextInt(10);  // [5 <= n < 15]
        Point2D.Double[] pts = new Point2D.Double[n];
        for(int j = 0; j < n; j++) {
            pts[j] = new Point2D.Double();
            pts[j].x = seed.nextInt(rect.width);
            pts[j].y = seed.nextInt(rect.height);
        Line2D.Double[] lines = new ConvexHull().getHull(pts);
        convexHull = new Path2D.Double();
        for(int j = 0; j < lines.length; j++) {
            convexHull.append(lines[j], true);
    public void actionPerformed(ActionEvent e) {
        clipImage = ((JCheckBox)e.getSource()).isSelected();
        repaint();
    private JPanel getUIPanel() {
        JCheckBox cb = new JCheckBox("clip", clipImage);
        cb.addActionListener(this);
        JPanel panel = new JPanel();
        panel.add(cb);
        return panel;
    public static void main(String[] args) throws IOException {
        String path = "images/hawk.jpg";
        BufferedImage image = ImageIO.read(new File(path));
        ConvexClip test = new ConvexClip(image);
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.add(test);
        f.add(test.getUIPanel(), "Last");
        f.setSize(400,400);
        f.setLocation(200,200);
        f.setVisible(true);
class ConvexHull {
    public Line2D.Double[] getHull(Point2D.Double[] points) {
        List<Line2D.Double> hull = new ArrayList<Line2D.Double>();
        double min = Integer.MAX_VALUE;
        int minIndex = -1;
        for(int i = 0; i < points.length; i++) {
            if(points.y <= min) {
min = points[i].y;
minIndex = i;
int start = minIndex;
double lastTheta = 0;
int next = -1;
// Find point with minimum angular displacement.
int count = points.length;
do {
next = getNextIndex(start, lastTheta, points);
hull.add(new Line2D.Double(points[start], points[next]));
lastTheta = getTheta(points[start], points[next]);
start = next;
} while(count-- > 0 && next != minIndex);
return hull.toArray(new Line2D.Double[hull.size()]);
private double getTheta(Point2D.Double p1, Point2D.Double p2) {
double dy = p2.y - p1.y;
double dx = p2.x - p1.x;
double theta = Math.atan2(dy, dx);
if(theta < 0)
theta += 2*Math.PI;
return theta;
private int getNextIndex(int index, double lastTheta,
Point2D.Double[] points) {
double min = Double.MAX_VALUE;
int minIndex = 0;
for(int i = 0; i < points.length; i++) {
if(i == index)
continue;
double theta = getTheta(points[index], points[i]);
if(theta == 0)
theta += 2*Math.PI;
if(theta < min && theta >= lastTheta) {
min = theta;
minIndex = i;
return minIndex;