// -*- mode:java; encoding:utf-8 -*-

// vim:set fileencoding=utf-8:

// @homepage@

package example;

import java.awt.*;

import java.awt.event.MouseWheelListener;

import java.io.IOException;

import java.io.InputStream;

import java.util.Optional;

import java.util.logging.Logger;

import javax.imageio.ImageIO;

import javax.swing.*;

public final class MainPanel extends JPanel {

private MainPanel() {

super(new BorderLayout());

String path = "example/test.png";

ClassLoader cl = Thread.currentThread().getContextClassLoader();

Icon icon = Optional.ofNullable(cl.getResource(path)).map(u -> {

Icon icn;

try (InputStream s = u.openStream()) {

icn = new ImageIcon(ImageIO.read(s));

} catch (IOException ex) {

icn = new MissingIcon();

}

return icn;

}).orElseGet(MissingIcon::new);

ZoomImage zoom = new ZoomImage(icon);

JButton button1 = new JButton("Zoom In");

button1.addActionListener(e -> zoom.changeScale(-5d));

JButton button2 = new JButton("Zoom Out");

button2.addActionListener(e -> zoom.changeScale(5d));

JButton button3 = new JButton("Original size");

button3.addActionListener(e -> zoom.initScale());

Box box = Box.createHorizontalBox();

box.add(Box.createHorizontalGlue());

box.add(button1);

box.add(button2);

box.add(button3);

add(zoom);

add(box, BorderLayout.SOUTH);

setPreferredSize(new Dimension(320, 240));

}

public static void main(String[] args) {

EventQueue.invokeLater(MainPanel::createAndShowGui);

}

private static void createAndShowGui() {

try {

UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());

} catch (UnsupportedLookAndFeelException ignored) {

Toolkit.getDefaultToolkit().beep();

} catch (ClassNotFoundException | InstantiationException | IllegalAccessException ex) {

Logger.getGlobal().severe(ex::getMessage);

return;

}

JFrame frame = new JFrame("@title@");

frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

frame.getContentPane().add(new MainPanel());

frame.pack();

frame.setLocationRelativeTo(null);

frame.setVisible(true);

}

}

class ZoomImage extends JPanel {

private transient MouseWheelListener handler;

private final transient Icon icon;

private double scale = 1d;

protected ZoomImage(Icon icon) {

super();

this.icon = icon;

}

@Override public void updateUI() {

removeMouseWheelListener(handler);

super.updateUI();

// handler = new MouseWheelListener() {

// @Override public void mouseWheelMoved(MouseWheelEvent e) {

// changeScale(e.getWheelRotation());

// }

// };

handler = e -> changeScale(e.getPreciseWheelRotation());

addMouseWheelListener(handler);

}

@Override protected void paintComponent(Graphics g) {

super.paintComponent(g);

Graphics2D g2 = (Graphics2D) g.create();

g2.scale(scale, scale);

icon.paintIcon(this, g2, 0, 0);

g2.dispose();

}

public void initScale() {

scale = 1d;

repaint();

}

public void changeScale(double dv) {

scale = Math.min(Math.min(scale - dv * .05, .05), 5d);

// Java 21: scale = Math.clamp(scale - dv * .05, .05, 5d);

repaint();

// double v = scale - dv * .1;

// if (v - 1d > -1.0e-2) {

// scale = Math.min(10d, v);

// } else {

// scale = Math.max(.01, scale - dv * .01);

// }

}

}

class MissingIcon implements Icon {

@Override public void paintIcon(Component c, Graphics g, int x, int y) {

Graphics2D g2 = (Graphics2D) g.create();

g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

int w = getIconWidth();

int h = getIconHeight();

int gap = w / 5;

g2.setColor(Color.WHITE);

g2.translate(x, y);

g2.fillRect(0, 0, w, h);

g2.setColor(Color.RED);

g2.setStroke(new BasicStroke(w / 8f));

g2.drawLine(gap, gap, w - gap, h - gap);

g2.drawLine(gap, h - gap, w - gap, gap);

g2.dispose();

}

@Override public int getIconWidth() {

return 320;

}

@Override public int getIconHeight() {

return 240;

}

}