java - JFrame the same shape as an Image / Program running in background

Question

My question is simple, the solution surely not. I am looking for a way to shape a JFrame the same as an Image it will be displaying. By shape I mean the shape of the pixels that have an alpha != 0. I've already found a working example using a GeneralPath object, but it created ~110000 "nodes" for an Image of about 500*400, so starting the JFrame took more than 2 minutes, which is definitely not the desired effect, the startup should be in under 2 seconds.

Thanks for your time.

Answer 1

I personally would ditch the window shape in favor of a transparent window, it's just simpler for what you are trying to do...

And with the close button (look to the bottom left)

The red border around the image is deliberate, as it shows the "window" bounds.

This relies on either Java 1.7 or Java 1.6_10+, there are checks in the code.

public class TransparentFrame {

    public static void main(String[] args) {
        new TransparentFrame();
    }

    public TransparentFrame() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (Exception ex) {
                }

                JFrame frame = new JFrame("Testing");
                frame.setUndecorated(true);
                frame.setContentPane(new ContentPane());

                String version = System.getProperty("java.version");
                System.out.println(version);
                if (version.startsWith("1.7")) {
                    frame.setBackground(new Color(0, 0, 0, 0));
                } else if (version.startsWith("1.6")) {
                    if (supportsPerAlphaPixel()) {
                        setOpaque(frame, false);
                    } else {
                        System.out.println("Per Pixel Alphering is not support with Java " + version);
                        System.exit(1);
                    }
                } else {
                    System.out.println("Per Pixel Alphering is not support with Java " + version);
                    System.exit(1);
                }
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new ImagePane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public static boolean supportsPerAlphaPixel() {

        boolean support = false;

        try {

            Class<?> awtUtilsClass = Class.forName("com.sun.awt.AWTUtilities");
            support = true;

        } catch (Exception exp) {
        }

        return support;

    }

    public static void setOpaque(Window window, boolean opaque) {

        try {

            Class<?> awtUtilsClass = Class.forName("com.sun.awt.AWTUtilities");
            if (awtUtilsClass != null) {

                Method method = awtUtilsClass.getMethod("setWindowOpaque", Window.class, boolean.class);
                method.invoke(null, window, opaque);

            }

        } catch (Exception exp) {
        }

    }

    public class ContentPane extends JPanel {

        public ContentPane() {
            setOpaque(false);
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            g.setColor(Color.RED);
            g.drawRect(0, 0, getWidth() - 1, getHeight() - 1);
        }
    }

    public class ImagePane extends JPanel {

        private BufferedImage background;
        private BufferedImage offImage;
        private Ellipse2D offButton;
        private boolean mouseIn;

        public ImagePane() {
            setOpaque(false);
            try {
                background = ImageIO.read(new File("tamagotchi400.png"));
                offImage = ImageIO.read(new File("powerSmall.png"));
            } catch (IOException ex) {
                ex.printStackTrace();
            }
            offButton = new Ellipse2D.Float(212, 330, 25, 25);
            MouseAdapter handler = new MouseAdapter() {
                @Override
                public void mouseClicked(MouseEvent e) {
                    if (e.getClickCount() == 1 && e.getButton() == MouseEvent.BUTTON1) {
                        if (offButton.contains(e.getPoint())) {
                            Window window = SwingUtilities.getWindowAncestor(ImagePane.this);
                            if (window != null) {
                                window.dispose();
                            }
                        }
                    }
                }

                @Override
                public void mouseMoved(MouseEvent e) {
                    Cursor cursor = Cursor.getDefaultCursor();
                    if (offButton.contains(e.getPoint())) {
                        cursor = Cursor.getPredefinedCursor(Cursor.HAND_CURSOR);
                    }
                    setCursor(cursor);
                }

                @Override
                public void mouseEntered(MouseEvent e) {
                    mouseIn = true;
                    repaint();
                }

                @Override
                public void mouseExited(MouseEvent e) {
                    mouseIn = false;
                    repaint();
                }
            };
            addMouseListener(handler);
            addMouseMotionListener(handler);
        }

        @Override
        public Dimension getPreferredSize() {
            return background == null ? new Dimension(400, 400) : new Dimension(background.getWidth(), background.getHeight());
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            if (background != null) {
                Graphics2D g2d = (Graphics2D) g.create();
                int x = (getWidth() - background.getWidth()) / 2;
                int y = (getHeight() - background.getHeight()) / 2;
                g2d.drawImage(background, x, y, this);
                if (mouseIn && offImage != null) {
                    g2d.drawImage(offImage, (int) offButton.getX(), (int) offButton.getY(), this);
                }
                g2d.dispose();
            }
        }
    }
}