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JFileChooser icons on 2K Displays

Any idea how to make the Java Swing file chooser
look better on 2K displays where the windows
font scaling is > 125%?
I am using ordinary code such as:
JFileChooser fc = new JFileChooser();
if (settings.currentdir != null)
fc.setCurrentDirectory(new File(settings.currentdir));
int returnVal = fc.showOpenDialog((Window) holder);
if (returnVal == JFileChooser.APPROVE_OPTION) {
But the file chooser is only displaying tiny
icons for the listed files and directories. I am using
JDK 8. What is going wrong?
P.S.: Scope of the question is only Windows, not
Unixes. On Windows, the two default L&F, they
scale the font. But they don't scale icons. The
application has to do that, since it might use
a different bitmap resources for higher scales.
It seems that JFileChooser is not coded this way.
But it might be that the JFileChooser can be
instructed to do so. I don't see that the
other question addresses icon size and the
JFileChooser on Windows: How to set the DPI of Java Swing apps on Windows/Linux? The
other question deals with font size, which is
not an issue for the JFileChooser on Windows with
one of the two Windows L&F.

Just a quick idea while i came across this thread. You can try to deliver your own iconset:
new JFileChooser().setFileView(new FileView() {
#Override
public Icon getIcon(File f) {
return fancy2kIconForExtension(StringUtils.substringAfterLast("."));
}
});
be careful to load your Icons from a Cache, as this method is called very often from inside JFileChooser, otherwise you end up reloading icon all the time.

I very recently ran into same problem. the only work around is not using java build in ImageIcon class but to write one yourself,
This one took the provided image, scale it to fit current component size and paint it. I tried to make is as simple as possible and as close to original class as able, but its not perfect and need improvement, especially in component-icon alignment
import java.awt.Component;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.geom.AffineTransform;
import javax.swing.AbstractButton;
import javax.swing.ImageIcon;
/**
*
* #author Rastislav
*/
public class ScaleToFitAndAntialiasIcon extends ImageIcon{
private ImageIcon icon;
public ScaleToFitAndAntialiasIcon(ImageIcon icon)
{
this.icon = icon;
}
public int getIconWidth()
{
return icon.getIconWidth();
}
public int getIconHeight()
{
return icon.getIconHeight();
}
#Override
public void paintIcon(Component c, Graphics g, int x, int y)
{
Graphics2D g2d = (Graphics2D)g.create();
AffineTransform at = g2d.getTransform();
double scaleToFit = ((double)c.getHeight() / (double)icon.getIconHeight());
if((int)icon.getIconHeight()*scaleToFit == c.getHeight()){
scaleToFit = ((double)c.getHeight() / (double)icon.getIconHeight()) - 0.1;
}
AffineTransform scaled = AffineTransform.getScaleInstance(scaleToFit, scaleToFit);
at.concatenate( scaled );
g2d.setTransform( at );
//need improvement
/* int lineupMinus = (int)((double)icon.getIconWidth() *((double)c.getHeight() / (double)icon.getIconHeight()));
int lineup = (int)((double)icon.getIconWidth() * scaleToFit);
int ff = (int)(lineupMinus - lineup);
System.out.println(ff);
*/
g2d.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
g2d.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
g2d.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BICUBIC);
//improved code goes here
icon.paintIcon(c, g2d, x, 4);
if(c instanceof AbstractButton a){
a.setIconTextGap((int)(-icon.getIconWidth()/2));
}
g2d.dispose();
}
}

proper way to use Java java.awt.Graphics

I was asked by uni to create a 2d racing game in java.
we were told to use one jcomponent in a jframe.
we told to update the game by the swing timer and call repaint() somewhere appropriate in their.
I have now finished but all the way through my use of Graphics g was annoying me. for example below is my gameobject class that players and stuff derive from.
import java.awt.Component;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.File;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
/*
* Provides The basic functionality of Displaying a game object on the screen
* and methods able to change the image
*/
public class GameObject {
public Vector position = new Vector();
//image set up variables
protected BufferedImage[] buffImage;
protected ImageIcon icon = new ImageIcon();
protected int numberOfImages;
protected String filePrefix;
protected String fileExt;
//////////////interactive variables
//image
protected int imageNumber = 0;
public GameObject(int numOfImages, String filePre, String fileE)
{
//if this gives grief about constructors implement a custom initObject() method that can be overridden with super.
this.numberOfImages = numOfImages;
buffImage = new BufferedImage[numOfImages];
filePrefix = filePre;
fileExt = fileE;
}
//Adds images to array
protected void initImageArray()
{
for(int i = 0; i <numberOfImages; i++)
{
try{
buffImage[i] = (BufferedImage) ImageIO.read(new File(filePrefix + "/" + Integer.toString(i) + fileExt));
}
catch(Exception e)
{
System.out.println(e);
}
}
}
//Draws object to screen
public void draw(Graphics g, Component c){
icon.setImage(getNextImage());
icon.paintIcon(c, g, position.x, position.y);
}
//returns current image
protected BufferedImage getNextImage(){
return buffImage[imageNumber];
}
//
protected void increaseImageNumber(){
if(imageNumber < numberOfImages-1){
imageNumber++;
}
else{
imageNumber = 0;
}
}
protected void decreaseimageNumber(){
if(imageNumber > 0){
imageNumber--;
}else{
imageNumber = numberOfImages - 1;
}
}
}
The bit specifically i don't think im doing right is passing the same "Graphics g" parameter to every objects draw method. it works but when i tried to place 15 stars in the back ground and change their imageIcon image from one buffered image array to the next everything became very jarred. I put this down to sharing this one graphic class. It could also just be that we were told not to use a threaded solution but i think any new comp should be able to handle 17 images updating and changing. the update timer is at every 33 milliseconds.
Thank you to anyone who can help explain to me the best way to achieve what i was after or the proper use/sharing of the graphics object.

Setting multiple icons on JButton

I have a JButton which I have set a custom icon on. Now I want it to display another icon ontop of the one that is already displayed when I drag my mouse cursor over it but I can't figure out how to do it because if I use button.setIcon(icon); it will replace the icon that already is displayed. How would I do this in an as easy way as possible?

I have a JButton which I have set a custom icon on. Now I want it to
display another icon ontop of the one that is already displayed when I
drag my mouse cursor over it but I can't figure out how to do it
because if I use button.setIcon(icon); it will replace the icon that
already is displayed. How would I do this in an as easy way as
possible
I think thats about JButton.setRolloverIcon(myIcon);
JButton has implemented those methods in API
JButton.setIcon(myIcon);
JButton.setRolloverIcon(myIcon);
JButton.setPressedIcon(myIcon);
JButton.setDisabledIcon(myIcon);
for example

If your icons are already transparent you can easily implement your own Icon to combine the two -
public class CombineIcon implements Icon {
private Icon top;
private Icon bottom;
public CombineIcon(Icon top, Icon bottom) {
this.top = top;
this.bottom = bottom;
}
public int getIconHeight() {
return Math.max(top.getIconHeight(), bottom.getIconHeight());
}
public int getIconWidth() {
return Math.max(top.getIconWidth(), bottom.getIconWidth());
}
public void paintIcon(Component c, Graphics g, int x, int y) {
bottom.paintIcon(c, g, x, y);
top.paintIcon(c, g, x, y);
}
}
You use setRolloverIcon(icon) to specify the icon you want to show when the mouse is over the button.

Create a second version of that button icon which contains the overlay. On mouse over switch to the image with the overlay.
Another approach could be to combine the icon with its overlay to a new icon in memory and place it as an icon on the button. This might be a good approach if your icons are frequently changing. If that's not the case I would definitely use the first approach.

I find this pretty easy.
import java.awt.*;
import java.awt.image.BufferedImage;
import java.net.URL;
import javax.imageio.ImageIO;
import javax.swing.*;
class CombinedIconButton {
public static BufferedImage getCombinedImage(BufferedImage i1, BufferedImage i2) {
if (i1.getHeight() != i2.getHeight()
|| i1.getWidth() != i2.getWidth()) {
throw new IllegalArgumentException("Images are not the same size!");
}
BufferedImage bi = new BufferedImage(
i1.getHeight(),
i1.getWidth(),
BufferedImage.TYPE_INT_ARGB);
Graphics g = bi.getGraphics();
g.drawImage(i1,0,0,null);
g.drawImage(i2,0,0,null);
g.dispose();
return bi;
}
public static void main(String[] args) throws Exception {
URL url1 = new URL("http://i.stack.imgur.com/gJmeJ.png"); // blue circle
URL url2 = new URL("http://i.stack.imgur.com/5v2TX.png"); // red triangle
final BufferedImage bi1 = ImageIO.read(url1);
final BufferedImage bi2 = ImageIO.read(url2);
final BufferedImage biC = getCombinedImage(bi1,bi2);
Runnable r = new Runnable() {
#Override
public void run() {
JPanel gui = new JPanel(new BorderLayout());
JToggleButton b = new JToggleButton();
b.setIcon(new ImageIcon(bi1));
b.setRolloverIcon(new ImageIcon(biC));
b.setSelectedIcon(new ImageIcon(bi2));
gui.add(b);
JOptionPane.showMessageDialog(null, gui);
}
};
// Swing GUIs should be created and updated on the EDT
// http://docs.oracle.com/javase/tutorial/uiswing/concurrency/initial.html
SwingUtilities.invokeLater(r);
}
}
Images borrowed from this answer.

One way to do that is:
Create an icon which you want to see when the pointer is hovered on top of the button by some image editing tool. And set that image once mousehover event occurs.
p.s. use any pic editing tool and you can easily create a overlay image.
I also saw now that there is a concept of roll over icon in AbsractButton class. You can use that as well.

Problems in Using JLabel to Display a Chosen Image File

I encountered a problem while I am trying to display an image after I clicked a button and chose image file within the "Choose File Dialog".
Initially, I was managed to display the chosen image in JLabel, but later I created a separate ActionListener, I think it started to go wrong since then. Whatever image I choose, the JLabel won't display it.
I debugged it, and sure that the file chooser does pass the image to ImageIcon, JLabel does get the value from ImageIcon, but it doesn't display the image even after revalidate() and repaint().
Here I attached my code for your kind reference!
(I trimmed the code for a clean look, so there might be some brackets left not useful)
package com.xxx.LoyalCardManager;
import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.sql.SQLException;
import java.util.ArrayList;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JSeparator;
import javax.swing.JTextField;
import javax.swing.filechooser.FileFilter;
public class LoyalCardManagerMain implements ActionListener{
private JFrame frame;
private DatabaseHandler db = new DatabaseHandler();
private JLabel labelPic;
private JButton buttonPic;
private File picFile = new File("");
private BufferedImage image;
/**
* Launch the application.
* #throws SQLException
* #throws ClassNotFoundException
*/
public static void main(String[] args) throws SQLException, ClassNotFoundException {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
LoyalCardManagerMain window = new LoyalCardManagerMain();
window.frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
}
/**
* Create the application.
*/
public LoyalCardManagerMain() {
// Database initialisation
initDatabase();
// Draw GUI
frame = new JFrame();
frame.setBounds(100, 100, 619, 487);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().setLayout(null);
buttonPic = new JButton("Click to Choose Pic");
buttonPic.setBounds(415, 252, 166, 29);
frame.getContentPane().add(buttonPic);
buttonPic.setEnabled(false);
buttonPic.setActionCommand("ChoosePic");
buttonPic.addActionListener(this);
labelPic = new JLabel();
labelPic.setBounds(415, 30, 167, 210);
frame.getContentPane().add(labelPic);
}
public void actionPerformed(ActionEvent event) {
String command = event.getActionCommand();
if (command.equals("ChoosePic")) {
//TODO Label now cannot display images.
JFileChooser chooser = new JFileChooser();
chooser.setFileSelectionMode(JFileChooser.FILES_AND_DIRECTORIES);
chooser.setAcceptAllFileFilterUsed(false);
chooser.setFileFilter(new FileFilter() {
public boolean accept (File f) {
String extension = Utils.getExtension(f);
if(extension != null) {
if (extension.equals(Utils.gif) ||
extension.equals(Utils.jpeg) ||
extension.equals(Utils.jpg) ||
extension.equals(Utils.png) ||
extension.equals(Utils.tif) ||
extension.equals(Utils.tiff)) {
return true;
}else{
return false;
}
}
return false;
}
public String getDescription() {
return "Image File (*.gif, *.jpeg, *.jpg, *.png, *.tif, *.tiff)";
}
});
int retVal = chooser.showOpenDialog(frame);
if (retVal == JFileChooser.APPROVE_OPTION) {
picFile = chooser.getSelectedFile();
try {
image = ImageIO.read(picFile);
} catch (IOException e) {
e.printStackTrace();
}
// Calculate the pic's ratio and do re-scale
double ratio = (double) labelPic.getWidth() / (double) labelPic.getHeight();
// Do image scale, scaledW is the new Width, and LabelPic.getHeight is the new Height.
int scaledW = (int) (image.getHeight() * ratio);
image = new BufferedImage(scaledW, labelPic.getHeight(), BufferedImage.SCALE_FAST);
ImageIcon icon = new ImageIcon(image);
labelPic.setVisible(true);
labelPic.setIcon(icon);
labelPic.revalidate();
labelPic.repaint();
}
}
}
}
I also referenced other similar questions:
image loading using a JFileChooser into a JFrame
Image won't display in JLabel
Updating an image contained in a JLabel - problems
External Site: JFIleChooser opening image to JLabel
As well as Java Tutorial Docs
How to Use Buttons, Check Boxes, and Radio Buttons
But I still can't figure it out why the JLabel not display the chosen image.
Thanks for your kind help mates!

Ok, I finally figured out what's wrong with the code:
If I intend to use BufferedImage to resize (sorry, in my question I mis-understanding the method scale with resize), I need to use drawImage method to "redraw" the image. Otherwise the image will not be shown.
I made modification here:
double ratio = (double) labelPic.getWidth() / (double) labelPic.getHeight();
// Do image scale, scaledW is the new Width, and LabelPic.getHeight is the new Height.
int scaledW = (int) (image.getHeight() * ratio);
image = new BufferedImage(scaledW, labelPic.getHeight(), BufferedImage.SCALE_FAST);// Edit here
ImageIcon icon = new ImageIcon(image);
labelPic.setVisible(true);
labelPic.setIcon(icon);
labelPic.revalidate();
labelPic.repaint();
From the "Edit Here" mark, I use the following code:
BufferedImage imageTemp = new BufferedImage(resizedW, resizedH, BufferedImage.TYPE_INT_RGB);
imageTemp.getGraphics().drawImage(image,0,0, scaledW, scaledH, null);
image = imageTemp;
And there's difference between first pass the value to imageTemp then pass to image and directly pass the value to image. If I pass the new BufferedImage directly to image, it will display a pure black colour instead of the image you choose.

Try using this to display the image:
JfileChooser getImage = new JFileChooser();
..........
ImageIcon imagePath= new ImageIcon(getImage.getPath());
JLabel imageLabel= new JLabel() {
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawImage(imagePath.getImage(), 0, 0, width, height, null);
}
};
imageLabel.setLocation(10, 40);
imageLabel.setBorder(viewAnimalPanelBorder);
imageLabel.setSize(200, newHeight);
panel.add(imageLabel);
Let me know if you require more assistance.
Also, try displaying the picture without using the JFileChooser, maybe hard code the path for a test.

how to obtain mouse click coordinates outside my window in Java

I need to implement a class, using Swing, which can obtain the mouse coordinates when the user clicks anywhere on the screen. if I wanted to obtain the mouse coordinates inside my own window, I'd use a MouseListener, but I want it to work even when the user clicks outside my program.
I want my class to behave just like KColorChooser: the user clicks on the drop button and he can click anywhere on the screen to obtain the color of that spot. but I don't know if that's possible using pure Java.

It is possible though limited:
Add an AWTEventListener for focus events. As long as your app has focus before the button is clicked you'll receive a focus lost event. Then query for the pointer position.
The limitation is that, of course, your app loses focus. So depending on what you are ultimately trying to achieve this might not be useful.
If you don't want to lose focus then you will have to temporarily take a screenshot of the whole screen and display that in a screen filling window which listens for a mouse click as usual.
Proof of first method:
import java.awt.AWTEvent;
import java.awt.MouseInfo;
import java.awt.Toolkit;
import java.awt.event.AWTEventListener;
import javax.swing.JFrame;
public class Application1 {
public static void main(String[] args) {
Toolkit.getDefaultToolkit().addAWTEventListener(
new Listener(), AWTEvent.MOUSE_EVENT_MASK | AWTEvent.FOCUS_EVENT_MASK);
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
private static class Listener implements AWTEventListener {
public void eventDispatched(AWTEvent event) {
System.out.print(MouseInfo.getPointerInfo().getLocation() + " | ");
System.out.println(event);
}
}
}
Clicking outside of the app produced:
java.awt.Point[x=198,y=59] | java.awt.event.MouseEvent[MOUSE_EXITED, ...
java.awt.Point[x=976,y=503] | java.awt.FocusEvent[FOCUS_LOST, ...
The second point is outside of the app.

Forget about GlassPane, there's another 100% native Java way to do it that works both on OS X and on Windows.
Java has always supported translucency for its windows on OS X and Java now supports translucency for its windows on Windows too (since Java 1.6.0_10 or so, needs to be checked).
So the trick is: upon clicking on the "pick a color" tool, you create a nearly transparent borderless Java window covering the entire screen. You set its alpha to 10 (alpha goes from 0 to 255). That alpha is so low the user won't notice that there's a very thin "nearly transparent but only very very very translucent" borderless window covering the entire screen.
Now when the user clicks on your "alpha set to 10 translucent borderless window" covering the entire screen, you get your (x,y).
Discard the borderless Java window.
Use Robot's getRgb(x,y) and you're done.
Why set the alpha to 10 and not 0? Because otherwise clicks aren't intercepted by Java but go directly to the OS (at least that's how it works for a fact on OS X). There's a treshold and I know it's not set at '1', nor '2', it's around 10 or so.
EDIT I just realized you know need to pick several colors, this is trickier but can still be done using 100% Java. Either you can live with "slightly off" colors (affected by the "nearly transparent" 'invisible' layer) or upon getting a click you must remove the layer, get the correct pixel color, and put again a "nearly transparent" layer. Now of course that is one heck of a hack but it can be done in 100% Java.

Use
import java.awt.MouseInfo;
import java.awt.Point;
import java.awt.PointerInfo;
PointerInfo inf = MouseInfo.getPointerInfo();
Point p = inf.getLocation();
p.x and p.y will give you co-ordinates outside your window.

I don't know if that's possible using
pure Java.
Its not possible using pure Java, since Java is only aware of MouseEvents on Windows belonging to Java.

These events are directed to the window which has the focus, from all events on the desktop you can only get the mouse position.
As already shown by Keilly it's only possible to get the mouse postion.
You need to include a native lib

I haven't tried this myself, but maybe you could create a full-screen, transparent panel/frame/etc, and add a MouseListener to that.

It is possible with a little trick. Should be 100% cross-platform (tested on Linux & Windows). Basically, you create a small JWindow, make it "alwaysOnTop" and move it around with the mouse using a timer.
For details, see my answer here.

The location (x,y) and the time interval
(d) between each click is supplied thru command line arguments. Here is the
program
import java.awt.* ;
import java.util.* ;
public final class ClickMouse extends TimerTask {
public static int x, y, d ;
public static void main(String[] args) {
TimerTask clikMouse = new ClickMouse();
Timer t = new Timer();
/*
x = Integer.parseInt(args[0]) ;
y = Integer.parseInt(args[1]) ;
d = Integer.parseInt(ares[2]) ;
*/
x = 500;
y = 200;
d = 5;
t.schedule(clikMouse,1000,d*1000);
}
public void run() {
try
{
Robot bot = new Robot();
bot.mouseMove(x,y);
bot.mousePress(java.awt.event.InputEvent.BUTTON1_MASK );
bot.mouseRelease(java.awt.event.InputEvent.BUTTON1_MASK);
}
catch (Exception e)
{
System.out.println("Exception occured :" + e.getMessage());
}
}
}

https://github.com/kwhat/jnativehook JNativeHook: Global keyboard and mouse listeners for Java.

I don't have enough rep yet to leave comments, but here are my comments on the other techniques:
Use a native lib: will work, but has obvious distribution limitations
Use GlassPane to fill entire screen: GlassPanes must be contained within a Window.
Create a Window containing a picture of the desktop and fill the entire screen: Will work, but it will suddenly make the desktop static. The cursor will no longer change, any animations or video in other windows or desktop will become eerily static.
Alternative solution:
A refinement of the screen filling window, if you are using Java 6u10 or later is to make the window completely transparent. Put this window in front of all others and listen for mouse clicks. It still has shortcomings, such as no cursor changes, but it depends on what you want to do.

Based on SyntaxT3rr0r's answer I created a sample color picker in groovy which shows how it can work.
import java.awt.*
import java.awt.datatransfer.*
//import com.sun.awt.AWTUtilities;
import javax.swing.WindowConstants as WC;
import javax.swing.SwingConstants as SWC
import groovy.swing.SwingBuilder
class ColorPicker {
SwingBuilder swb = new SwingBuilder()
def window;
def overlayWindow
def mainPanel;
def mainLabel;
def menu;
def transparent = new Color(0, 0, 0, 0);
def nearlyTransparent = new Color(0, 0, 0, 26);
Color color = new Color(150, 150, 255);
def colorHex = { col ->
col = col?: color;
"#"+Integer.toHexString(col.getRGB())[2..-1]
}
def getTextColor = { baseColor ->
baseColor = baseColor?: color;
(baseColor.red*1.5 + baseColor.green*1.5 + baseColor.blue > 400) ? Color.BLACK : Color.WHITE;
}
def setDisplayColor = {newColor ->
mainPanel.background = newColor
mainLabel.foreground = getTextColor(newColor)
mainLabel.text = colorHex(newColor)
}
def show(){
menu = swb.popupMenu { // invoker: mainPanel
menuItem(text: "Pick Color", actionPerformed: capturePixelColor)
menuItem(text: "Copy to Clipboard", actionPerformed: {
Clipboard clipboard = Toolkit.getDefaultToolkit().getSystemClipboard();
clipboard.setContents(new StringSelection(colorHex()), null);
})
separator()
menuItem(text: "Close", actionPerformed: {dispose()})
}
window = swb.frame(
title: "Color Picker",
location:[50,50],
size:[60, 60],
resizable: false,
undecorated: true,
alwaysOnTop: true,
defaultCloseOperation:WC.EXIT_ON_CLOSE
){
def textColor = getTextColor()
mainPanel = panel( constraints: BorderLayout.CENTER,
border: lineBorder(color: Color.BLACK),
componentPopupMenu: menu){
borderLayout()
mainLabel = label(text: "--",
constraints: BorderLayout.CENTER,
horizontalAlignment: SWC.CENTER)
}
}
setDisplayColor(color);
window.show();
}
def capturePixelColor = {
def screenSize = Toolkit.getDefaultToolkit().screenSize
overlayWindow = swb.frame(
location:[0,0],
size: screenSize,
resizable: false,
undecorated: true,
alwaysOnTop: true,
defaultCloseOperation:WC.DISPOSE_ON_CLOSE,
show: true,
background: nearlyTransparent, // AWTUtilities.setWindowOpacity(overlayWindow, 0.1f);
cursor: Cursor.CROSSHAIR_CURSOR,
mouseClicked: {event ->
int x = event.getXOnScreen() // or maybe getX() is enough
int y = event.getYOnScreen()
overlayWindow.dispose()
overlayWindow = null
color = new Robot().getPixelColor(x, y)
setDisplayColor(color)
}
)
}
public static void main(String...args){
println "Welcome to ColorPicker"
def picker = new ColorPicker()
picker.show()
}
}

Look, I understand I am 7 years late...
This is a re-make of Keilly's answer, which allows to get when the mouse button is clicked, anywhere. The main problem is that fullscreen games are always unfocused, and it becomes annoying to handle.
Here is the code:
import java.awt.AWTEvent;
import java.awt.MouseInfo;
import java.awt.Point;
import java.awt.Toolkit;
import java.awt.event.AWTEventListener;
import javax.swing.JFrame;
public class Main {
public static JFrame frame = new JFrame();
public static void main(String[] args) {
Toolkit.getDefaultToolkit().addAWTEventListener(
new Listener(), AWTEvent.MOUSE_EVENT_MASK | AWTEvent.FOCUS_EVENT_MASK);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
frame.setAlwaysOnTop(true);
frame.setLocation(1, 1);
}
private static class Listener implements AWTEventListener {
public void eventDispatched(AWTEvent event) {
// We do not want the event to show twice,
// as it shows for focusing and unfocusing
if(event.getID() == 1004) {
Point p = MouseInfo.getPointerInfo().getLocation();
System.out.println("Mouse Clicked at " + p.x + ", " + p.y);
}
// The frame was just unfocused! To make
// sure we get the next mouse click, we
// need to focus it again!
frame.setVisible(true);
}
}
}