Java2D (WeatherWizard)

package com.han.java2d;

import javax.imageio.ImageIO;
import javax.swing.*;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
import java.awt.*;
import java.awt.font.FontRenderContext;
import java.awt.geom.Rectangle2D;
import java.awt.image.BufferedImage;
import java.net.URL;

/**
 * The WeatherWizard demo uses the JSlider component as well as various graphics capabilities to generate and display
 * a specified weather type.<p>
 * Class note: Created by Gaowen on 14-1-11.
 */
public class WeatherWizard extends JPanel implements ChangeListener {
    private final WeatherPainter painter;

    private WeatherWizard() {
        setLayout(new BorderLayout());
        Box box = Box.createHorizontalBox();
        box.add(Box.createGlue());
        box.add(new JLabel("Temperature:"));
        JSlider jSlider = new JSlider(20, 100, 65);
        jSlider.setMinorTickSpacing(5);
        jSlider.setMajorTickSpacing(20);
        jSlider.setPaintTicks(true);
        jSlider.setPaintLabels(true);
        jSlider.addChangeListener(this);
        box.add(jSlider);
        box.add(Box.createGlue());
        add(box, BorderLayout.NORTH);
        painter = new WeatherPainter(loadImage("sun"), loadImage("cloud"), loadImage("rain"), loadImage("snow"));
        add(painter, BorderLayout.CENTER);
    }

    private BufferedImage loadImage(String name) {
        String imgFileName = "images/weather-" + name + ".png";
        URL url = WeatherWizard.class.getResource(imgFileName);
        BufferedImage img = null;
        try {
            img = ImageIO.read(url);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return img;
    }

    private class WeatherPainter extends Component {
        private final BufferedImage snow;
        private final BufferedImage rain;
        private final BufferedImage cloud;
        private final BufferedImage sun;
        private int temperature;
        private Color textColor;
        private String feels;
        private String condStr;
        private Composite alpha0;
        private Composite alpha1;
        private BufferedImage img0;
        private BufferedImage img1;

        private WeatherPainter(BufferedImage snow, BufferedImage rain, BufferedImage cloud, BufferedImage sun) {
            this.snow = snow;
            this.rain = rain;
            this.cloud = cloud;
            this.sun = sun;
            temperature = 65;
            textColor = Color.yellow;
        }

        public void setTemperature(int temperature) {
            this.temperature = temperature;
            repaint();
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(450, 125);
        }

        @Override
        public void paint(Graphics g) {
            Graphics2D g2 = (Graphics2D) g.create();
            Dimension size = getSize();
            Composite origComposite;
            setupWeatherReport();
            origComposite = g2.getComposite();
            if (alpha0 != null) g2.setComposite(alpha0);
            g2.drawImage(img0, 0, 0, size.width, size.height, 0, 0, img0.getWidth(null), img0.getHeight(null), null);
            if (img1 != null) {
                if (alpha1 != null) g2.setComposite(alpha1);
                g2.drawImage(img1, 0, 0, size.width, size.height, 0, 0, img1.getWidth(null), img1.getHeight(null),
                        null);
            }
            g2.setComposite(origComposite);
            Font font = new Font("Serif", Font.PLAIN, 36);
            g2.setFont(font);
            String tempString = feels + " " + temperature + "F";
            FontRenderContext frc = g2.getFontRenderContext();
            Rectangle2D boundsTemp = font.getStringBounds(tempString, frc);
            Rectangle2D boundsCond = font.getStringBounds(condStr, frc);
            int wText = Math.max((int) boundsTemp.getWidth(), (int) boundsCond.getWidth());
            int hText = (int) boundsTemp.getHeight() + (int) boundsCond.getHeight();
            int rX = (size.width - wText) / 2;
            int rY = (size.height - hText) / 2;
            g2.setColor(Color.LIGHT_GRAY);
            g2.fillRect(rX, rY, wText, hText);
            g2.setColor(textColor);
            int xTextTemp = rX - (int) boundsTemp.getX();
            int yTextTemp = rY - (int) boundsTemp.getY();
            g2.drawString(tempString, xTextTemp, yTextTemp);
            int xTextCond = rX - (int) boundsCond.getX();
            int yTextCond = rY - (int) boundsCond.getY() + (int) boundsTemp.getHeight();
            g2.drawString(condStr, xTextCond, yTextCond);
        }

        private void setupWeatherReport() {
            if (temperature <= 32) {
                setupImages(snow);
                setupText("Snow", null);
            } else if (temperature <= 40) {
                setupImages(32, 40, snow, rain);
                setupText("Snow", "Rain");
            } else if (temperature <= 50) {
                setupImages(rain);
                setupText("Rain", null);
            } else if (temperature <= 58) {
                setupImages(50, 58, rain, cloud);
                setupText("Rain", "Cloud");
            } else if (temperature <= 65) {
                setupImages(cloud);
                setupText("Cloud", null);
            } else if (temperature <= 75) {
                setupImages(65, 75, cloud, sun);
                setupText("Cloud", "Sun");
            } else {
                setupImages(sun);
                setupText("Sun", null);
            }
        }

        private void setupText(String s1, String s2) {
            if (temperature <= 32) {
                textColor = Color.blue;
                feels = "Freezing";
            } else if (temperature <= 50) {
                textColor = Color.green;
                feels = "Cold";
            } else if (temperature <= 65) {
                textColor = Color.yellow;
                feels = "Cool";
            } else if (temperature <= 75) {
                textColor = Color.orange;
                feels = "Warm";
            } else {
                textColor = Color.red;
                feels = "Hot";
            }
            condStr = s1;
            if (s2 != null) {
                condStr += "/" + s2;
            }
        }

        private void setupImages(BufferedImage i0) {
            alpha0 = null;
            alpha1 = null;
            img0 = i0;
            img1 = null;
        }

        private void setupImages(int min, int max, BufferedImage i0, BufferedImage i1) {
            float alpha = (max - temperature) / (float) (max - min);
            alpha0 = AlphaComposite.getInstance(AlphaComposite.SRC_OVER, alpha);
            alpha1 = AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 1 - alpha);
            img0 = i0;
            img1 = i1;
        }
    }

    @Override
    public void stateChanged(ChangeEvent e) {
        JSlider jSlider = (JSlider) e.getSource();
        painter.setTemperature(jSlider.getValue());
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                createAndShowGUI();
            }
        });
    }

    private static void createAndShowGUI() {
        JFrame jFrame = new JFrame("Weather Wizard");
        JPanel contentPane = new WeatherWizard();
        jFrame.setContentPane(contentPane);
        jFrame.pack();
        jFrame.setLocationRelativeTo(null);
        jFrame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        jFrame.setVisible(true);
    }
}