Images and Transparency

Question

Ok, so I have a program wwhich displays 2 Images, one on top of the other.
The first one (rendered first) is an image loaded from a file which is completely opaque.
The second one starts off as completely transparent, but every time you click on it, a semi-transparent square appears.
The only problem is that if you click again on the same square it adds another semi-transparent square on top, making it more opaque.
I was wondering if there is an easy way to make it draw a semi-transparent sqaure the first time I click, and do nothing the second time.
Is it possible to do this using AWT instead of keeping a record of which squares have been drawn?
Relevant code below, overlay is the image concerned and graphics is its Graphics object.
private int tileWidth = 16;
private int tileHeight = 16;
private Color fillColor = new Color(255, 255, 255, 192);
private BufferedImage overlay;
private Graphics graphics;
private int mapHeight;
private int mapWidth;
Constructor() {
     overlay = new BufferedImage(mapWidth, mapHeight, BufferedImage.TYPE_INT_ARGB);
     graphics = overlay.createGraphics();
     graphics.setColor(new Color(255, 255, 255, 0));
     graphics.fillRect(0, 0, mapWidth, mapHeight);
     repaint();
     revalidate();
public void paintComponent(Graphics g) {
     g.drawImage(map, 0, 0, this);
     g.drawImage(overlay, 0, 0, this);
public void mousePressed(MouseEvent e) {
     fillTile(e.getX(), e.getY());
public void mouseDragged(MouseEvent e) {
     fillTile(e.getX(), e.getY());     
private void fillTile(int x, int y) {
     int tileX = (x / tileWidth) * tileWidth;
     int tileY = (y / tileHeight) * tileHeight;
     if (graphics != null) {
          graphics.setColor(fillColor);
          graphics.fillRect(tileX, tileY, tileWidth, tileHeight);
          repaint();
}

Answer 1

import java.awt.*;
import java.awt.image.*;
import java.awt.event.*;
import java.io.File;
import javax.swing.*;
public class ImageTest extends JComponent implements MouseListener,
          MouseMotionListener {
     private int tileWidth = 16;
     private int tileHeight = 16;
     private Color fillColor = new Color(255, 255, 255, 192);
     private File imageFile;
     private Image bg;
     private BufferedImage overlay;
     private Graphics graphics;
     private int bgHeight;
     private int bgWidth;
     private JFrame frame;
     private JScrollPane jsp;
     private ImageTest() {
          createAndShowGUI();
            * Replace FILE NAME HERE with the path of the image file.
          imageFile = loadFile("FILE NAME HERE");
          if (imageFile != null) {
               bg = loadImage(imageFile);
          if (bg != null) {
               bgWidth = bg.getWidth(this);
               bgHeight = bg.getHeight(this);
               overlay = new BufferedImage(bgWidth, bgHeight,
                         BufferedImage.TYPE_INT_ARGB);
               graphics = overlay.createGraphics();
               graphics.setColor(new Color(255, 255, 255, 0));
               graphics.fillRect(0, 0, bgWidth, bgHeight);
          repaint();
          revalidate();
     private void createAndShowGUI() {
          try {
               UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
          } catch (Exception e) {
               // Can't use system look and feel.
          frame = new JFrame("ImageTest");
          frame.setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
          addMouseListener(this);
          addMouseMotionListener(this);
          jsp = new JScrollPane(this,
                    ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED,
                    ScrollPaneConstants.HORIZONTAL_SCROLLBAR_AS_NEEDED);
          frame.getContentPane().add(jsp);
          frame.pack();
          frame.setSize(800, 600);
          frame.setVisible(true);
     public Dimension getPreferredSize() {
          if (bg != null)
               return new Dimension(bgWidth, bgHeight);
          return new Dimension(800, 600);
     public void paintComponent(Graphics g) {
          g.drawImage(bg, 0, 0, this);
          g.drawImage(overlay, 0, 0, this);
     public void mouseClicked(MouseEvent e) {
     public void mouseEntered(MouseEvent e) {
     public void mouseExited(MouseEvent e) {
     public void mouseReleased(MouseEvent e) {
     public void mouseMoved(MouseEvent e) {
     public void mousePressed(MouseEvent e) {
          fillTile(e.getX(), e.getY());
     public void mouseDragged(MouseEvent e) {
          fillTile(e.getX(), e.getY());
     private void fillTile(int x, int y) {
          int tileX = (x / tileWidth) * tileWidth;
          int tileY = (y / tileHeight) * tileHeight;
          if (graphics != null) {
               graphics.setColor(fillColor);
               graphics.fillRect(tileX, tileY, tileWidth, tileHeight);
               repaint();
     private File loadFile(String fileName) {
          File file = new File(fileName);
          try {
               if (!file.exists()) {
                    System.err.println(fileName + " does not exist.");
                    return null;
          } catch (SecurityException e) {
               System.err.println("Access denied to " + fileName + ".");
               return null;
          return file;
     private Image loadImage(File imageFile) {
          String imageName = imageFile.getAbsolutePath();
          try {
               if (imageFile.canRead()) {
                    Image i;
                    i = Toolkit.getDefaultToolkit().createImage(imageName);
                    MediaTracker media = new MediaTracker(this);
                    media.addImage(i, 0);
                    media.waitForID(0);
                    return i;
               System.err.println("Cannot read " + imageName + ".");
               return null;
          } catch (SecurityException e) {
               System.err.println("Access denied to " + imageName + ".");
               return null;
          } catch (InterruptedException e) {
               System.err.println("Loading " + imageName + " interrupted.");
               return null;
     public static void main(String[] args) {
          new ImageTest();
}Remember to replace FILE NAME HERE with the path of an image file.
A good one to use would be [this one|http://www.vgmaps.com/Atlas/GB-GBC/LegendOfZelda-OracleOfAges-Labrynna%28Present%29.png] as that is what I am using.
Edited by: KrimsonEagl on 30/11/2009 22:07