// TAlphaComposite.java

import java.awt.*;
import java.awt.event.*;
import java.awt.font.*;
import java.awt.geom.*;
import java.awt.image.*;
import javax.swing.*;
import javax.swing.event.*;


class TAlphaComposite extends JFrame {
    DrawingCanvas canvas;
    JSlider slider, sliderAlpha;
    JComboBox rulesBox;

    // Labels for Porter Duff Rules, and the corresponding fields in
    // the class AlphaComposite.
    String[] rulesLabels = {"Clear", "Source",
                            "Source-over", "Destination-over",
                            "Source-in", "Destination-in",
                            "Source-out", "Destination-out"};
    int[] rules = {AlphaComposite.CLEAR, AlphaComposite.SRC,
                   AlphaComposite.SRC_OVER, AlphaComposite.DST_OVER,
                   AlphaComposite.SRC_IN, AlphaComposite.DST_IN,
                   AlphaComposite.SRC_OUT, AlphaComposite.DST_OUT};
    
    public TAlphaComposite() {
        // 1. Assign a name to the frame, and obtain its
        // content pane.
        super("TAlphaComposite");
        Container container = getContentPane();

        // 2. Create a canvas and add it to the frame
        canvas = new DrawingCanvas();
        container.add(canvas);

        // 3. Create a rules combo box, and alpha adjustment slider
        // in a panel, and add them panel to the frame.
        rulesBox = new JComboBox(rulesLabels);
        rulesBox.setSelectedIndex(0);
        rulesBox.setAlignmentX(Component.LEFT_ALIGNMENT);
        rulesBox.addActionListener(new ComboBoxListener());

        setSlider(0, 100, 100, 25, 5);
        sliderAlpha = slider;

        JPanel panel = new JPanel();
        panel.setLayout(new GridLayout(1,3));
        panel.add(rulesBox);
        panel.add(new JLabel("Alpha Adjustment x E-2: ", JLabel.RIGHT));
        panel.add(sliderAlpha);
        container.add(panel, BorderLayout.SOUTH);

        // 4. Add a window closing listener and display it a suitable size
        addWindowListener(new WindowEventHandler());
        pack();
        show();
    }

    // 5. Code to handle the closing of frame
    class WindowEventHandler extends WindowAdapter {
        public void windowClosing(WindowEvent e) {
            System.exit(0);
        }
    }

    // 6. Method to create sliders with necessary configuration
    public void setSlider(int min, int max, int init,
                          int mjrTkSp, int mnrTkSp) {
        slider = new JSlider(JSlider.HORIZONTAL, min, max, init);
        slider.setPaintTicks(true);
        slider.setMajorTickSpacing(mjrTkSp);
        slider.setMinorTickSpacing(mnrTkSp);
        slider.setPaintLabels(true);
        slider.addChangeListener(new SliderListener());
    }

    // 7. The main method...
    public static void main(String arg[]) {
        new TAlphaComposite();
    }

    // 8. Slider listener class
    class SliderListener implements ChangeListener {
        public void stateChanged(ChangeEvent e) {
            JSlider slider = (JSlider) e.getSource();
            canvas.alphaValue = (float) slider.getValue()/100;
            canvas.repaint();
        }
    }

    // 9. Combo box listener class
    class ComboBoxListener implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            JComboBox cb = (JComboBox) e.getSource();
            canvas.compositeRule = rules[cb.getSelectedIndex()];
            canvas.repaint();
        }
    }

}

// 10. Canvas to paint the overlapped ellipses
class DrawingCanvas extends Canvas {
    float alphaValue = 1.0f;
    int compositeRule = AlphaComposite.CLEAR;
    AlphaComposite ac;

    DrawingCanvas() {
        setSize(300, 300);
        setBackground(Color.white);
    }

    public void paint(Graphics g) {
        // 11. Set up the 2D graphics context
        Graphics2D g2D = (Graphics2D) g;

        // 12. Retrieve the size of the canvas
        int w = getSize().width;
        int h = getSize().height;

        // 13. Create a buffered image and obtain its graphics context
        BufferedImage bi = new BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB);
        Graphics2D big = bi.createGraphics();

        // 14. Define an alpha composite instance with the selected composite
        // rule and the alpha value.
        ac = AlphaComposite.getInstance(compositeRule, alphaValue);

        // 15. Create two overlapped ellipses with red and blue colors
        // Draw the destination ellipse in red color.
        big.setColor(Color.red);
        big.drawString("Destination", w/4, h/4);
        big.fill(new Ellipse2D.Double(0, h/3, 2*w/3, h/3)); 

        // Draw the source ellipse in blue color.
        big.setColor(Color.blue);
        big.drawString("Source", 3*w/4, h/4);
        // 16. Assign the composite object to the graphics context
        big.setComposite(ac);
        big.fill(new Ellipse2D.Double(w/3, h/3, 2*w/3, h/3));

        // 17. Finally display the buffered image.
        g2D.drawImage(bi, null, 0, 0);
    }
}