Java graphics2d transparency example

java2d-transparency.md

package com.zetcode;

import java.awt.AlphaComposite;
import java.awt.Color;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import javax.swing.JFrame;
import javax.swing.JPanel;

class Surface extends JPanel {    
    
    private void doDrawing(Graphics g) {        
        
        Graphics2D g2d = (Graphics2D) g.create();
        
        g2d.setPaint(Color.blue);

        for (int i = 1; i <= 10; i++) {
            
            float alpha = i * 0.1f;
            AlphaComposite alcom = AlphaComposite.getInstance(
                    AlphaComposite.SRC_OVER, alpha);
            g2d.setComposite(alcom);
            g2d.fillRect(50 * i, 20, 40, 40);
        }        
        
        g2d.dispose();
    }
        
    @Override
    public void paintComponent(Graphics g) {

        super.paintComponent(g);
        doDrawing(g);
    }
}

public class TransparentRectanglesEx extends JFrame {
    
    public TransparentRectanglesEx() {
        
        initUI();
    }
    
    private void initUI() {
                
        add(new Surface());
        
        setTitle("Transparent rectangles");
        setSize(590, 120);
        setLocationRelativeTo(null);            
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
    
    public static void main(String[] args) {
        
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {

                TransparentRectanglesEx ex = new TransparentRectanglesEx();
                ex.setVisible(true);
            }
        });
    }
}