Transición de imágenes al estilo PowerPoint

package com.bolivia.app;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import javax.imageio.ImageIO;
import javax.swing.JPanel;
import javax.swing.Timer;
/**
 * @web https://www.jc-mouse.net/
 * @author Mouse
 */
public class JPanelPPT extends JPanel{

    public enum CTRL{
        NEXT,
        PREVIOUS
    }
    private CTRL option;    
    private Dimension SIZE_PANEL            =       new Dimension(500,500);
    private List<BufferedImage> imagenList  =       new ArrayList<BufferedImage>();    
    private int index                       =       0;//imagen actual
    private Timer timer;
    private int speed                       =       10;//en milisegundos
    private int x                           =       0;
    private int y                           =       0;
    private int size_cut                    = -10;
    private boolean inTransition            =       false;

    /** Constructor de clase */
    public JPanelPPT()
    {
        super();        
        setSize(SIZE_PANEL);
        setVisible(true); 

        //se carga imagenes en memoria
        try {
            imagenList.add(0, ImageIO.read(this.getClass().getResource("/com/bolivia/app/images/photo1.jpg")));
            imagenList.add(1, ImageIO.read(this.getClass().getResource("/com/bolivia/app/images/photo2.jpg")));
            imagenList.add(2, ImageIO.read(this.getClass().getResource("/com/bolivia/app/images/photo3.jpg")));
            imagenList.add(3, ImageIO.read(this.getClass().getResource("/com/bolivia/app/images/photo4.jpg")));            
        } catch (IOException ex) {
            System.err.println( ex.getMessage() );
        }
    }

    @Override
    public void paintComponent(Graphics g){
        Graphics2D g2 =(Graphics2D) g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,RenderingHints.VALUE_ANTIALIAS_ON);                    
        drawTransition(g2);
    }

    /**
 * pinta el efecto de transicion
 */
    public void drawTransition(Graphics2D g2)
    {
        //imagen actual
        g2.drawImage(imagenList.get(index), x, y, getWidth(), getHeight(), null);        
        size_cut +=10;//incrementa
        if( size_cut>0 )
        {        
            //obtiene coordenadas de recorte
            int px = getWidth()/2-size_cut/2;
            int py = getHeight()/2-size_cut/2;
            if( px >= 0 )
            {                
                int sindex=0;
                if(option == CTRL.NEXT)                                    
                    sindex = ((index+1) < imagenList.size())?index+1:0;                    
                else if(option == CTRL.PREVIOUS)
                    sindex = ((index-1) >= 0)?index-1:imagenList.size()-1;                                    
                //extrae recorte de imagen siguiente/anterior y dibuja
                BufferedImage recorte = imagenList.get(sindex).getSubimage(px,py,size_cut,size_cut);                        
                g2.drawImage(recorte, px, py, recorte.getWidth(), recorte.getHeight(), null);                       
                g2.dispose();
            }else{
                timer.stop();
                inTransition=false;
                g2.dispose();
                if(option == CTRL.NEXT)
                {
                   index+=1;
                   if(index>=imagenList.size()) index=0;                    
                }                
                if(option == CTRL.PREVIOUS)
                {
                    index-=1;
                    if(index<0) index=imagenList.size()-1;
                }
                repaint();
                size_cut=-10;//reinicia 
            }
        }
    }

    /**
 * @param CTRL option
 */
    public void play(CTRL option)
    {   
        this.option = option;    
        inTransition = !inTransition;
        ActionListener animation = new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent ae) {
                repaint();//refresca panel
            }
        };        

        if(inTransition)
        {
            if(timer!=null)timer.stop();
            timer = new Timer(speed,animation);
            timer.start();       
        }
        //else timer.stop();

    }
}//JPanelPPT:end

//nueva instancia
JPanelPPT ppt= new JPanelPPT();
//se añade a la interfaz
add(ppt);
//para avanzar
ppt.play(JPanelPPT.CTRL.NEXT);
//para retroceder
ppt.play(JPanelPPT.CTRL.PREVIOUS);