Если размер кнопки в процессе работы приложения не изменяется и известен заранее, то всё относительно просто:
JButton button = new JButton(
new ImageIcon("/path/to/image.png")
.getImage()
.getScaledInstance(buttonHeight, buttonWidth, java.awt.Image.SCALE_SMOOTH)
);
А для автоматического масштабирования надо шибко камлать, однако:
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Image;
import java.awt.Insets;
import java.awt.event.ComponentAdapter;
import java.awt.event.ComponentEvent;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class TestButton {
public static void main(String[] args) {
new TestButton();
}
private BufferedImage master;
public TestButton() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
try {
master = ImageIO.read(new File("/path/to/image.png"));
JButton btn = new JButton() {
@Override
public Dimension getPreferredSize() {
return new Dimension(90, 50);
}
};
btn.addComponentListener(new ComponentAdapter() {
@Override
public void componentResized(ComponentEvent e) {
JButton btn = (JButton) e.getComponent();
Dimension size = btn.getSize();
Insets insets = btn.getInsets();
size.width -= insets.left + insets.right;
size.height -= insets.top + insets.bottom;
if (size.width > size.height) {
size.width = -1;
} else {
size.height = -1;
}
Image scaled = master.getScaledInstance(size.width, size.height, java.awt.Image.SCALE_SMOOTH);
btn.setIcon(new ImageIcon(scaled));
}
});
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(btn);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
} catch (IOException exp) {
exp.printStackTrace();
}
}
});
}
}
