[hardwired]

Code:

import java.awt.*;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import java.io.*;
import javax.imageio.ImageIO;
import javax.swing.*;

public class Collage extends JPanel {
    BufferedImage top;
    BufferedImage bottom;
    Point loc = new Point();

    public Collage(BufferedImage[] images) {
        top = images[0];
        bottom = images[1];
    }

    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        int x = (getWidth() - bottom.getWidth())/2;
        int y  = (getHeight() - bottom.getHeight())/2;
        g.drawImage(bottom, x, y, this);
        g.drawImage(top, loc.x, loc.y, this);
    }

    private void save() {
        int w = getWidth();
        int h = getHeight();
        int type = BufferedImage.TYPE_INT_RGB;
        BufferedImage save = new BufferedImage(w, h, type);
        Graphics2D g2 = save.createGraphics();
        paint(g2);
        g2.dispose();
        try {
            ImageIO.write(save, "jpg", new File("collage.jpg"));
        } catch(IOException e) {
            System.out.println("write error: " + e.getMessage());
        }
        ImageIcon icon = new ImageIcon(save);
        JOptionPane.showMessageDialog(this, icon, "save", -1);
    }

    private JPanel getSouth() {
        JButton button = new JButton("save");
        button.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                save();
            }
        });
        JPanel panel = new JPanel();
        panel.add(button);
        return panel;
    }

    public static void main(String[] args) throws IOException {
        String[] ids = { "hawk", "blackBear" };
        BufferedImage[] images = new BufferedImage[ids.length];
        for(int j = 0; j < images.length; j++) {
            String path = "images/" + ids[j] + ".jpg";
            images[j] = ImageIO.read(new File(path));
        }
        Collage test = new Collage(images);
        test.addMouseListener(test.ml);
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.add(test);
        f.add(test.getSouth(), "Last");
        f.setSize(400,400);
        f.setLocation(200,200);
        f.setVisible(true);
    }

    private MouseListener ml = new MouseAdapter() {
        public void mousePressed(MouseEvent e) {
            loc = e.getPoint();
            repaint();
        }
    };
}