PBO-C 7 : ImageViewer

import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import javax.swing.*;
import java.io.File;

public class ImageViewer
{
    private static final String VERSION = "Version 1.0";
    private static JFileChooser fileChooser = new JFileChooser(System.getProperty("user.dir"));
    private JFrame frame;
    private ImagePanel imagePanel;
    private JLabel filenameLabel;
    private JLabel statusLabel;
    private OFImage currentImage;

    public ImageViewer()
    {
        currentImage = null;
        makeFrame();
    }

    private void openFile()
    {
        int returnVal = fileChooser.showOpenDialog(frame);
        if (returnVal != JFileChooser.APPROVE_OPTION)
        {
            return;
        }
        File selectedFile = fileChooser.getSelectedFile();
        currentImage = ImageFileManager.loadImage(selectedFile);
        if (currentImage == null)
        {
            JOptionPane.showMessageDialog(frame, "The file was not in a recognized image file format.",
                    "Image Load Error", JOptionPane.ERROR_MESSAGE);
            return;
        }
        imagePanel.setImage(currentImage);
        showFilename(selectedFile.getPath());
        showStatus("File loaded.");
        frame.pack();
    }

    private void close()
    {
        currentImage = null;
        imagePanel.clearImage();
        showFilename(null);
    }

    private void quit()
    {
        System.exit(0);
    }

    private void makeDarker()
    {
        if (currentImage != null)
        {
            currentImage.darker();
            frame.repaint();
            showStatus("Applied: darker");
        }
        else
        {
            showStatus("No image loaded.");
        }
    }

    private void makeLighter()
    {
        if (currentImage != null)
        {
            currentImage.lighter();
            frame.repaint();
            showStatus("Applied: lighter");
        }
        else
        {
            showStatus("No image loaded.");
        }
    }

    private void threshold()
    {
        if (currentImage != null)
        {
            currentImage.threshold();
            frame.repaint();
            showStatus("Applied: threshold");
        }
        else
        {
            showStatus("No image loaded.");
        }
    }

    private void showAbout()
    {
        JOptionPane.showMessageDialog(frame, "ImageViewer\n" + VERSION, "About ImageViewer",JOptionPane.INFORMATION_MESSAGE);
    }

    private void showFilename(String filename)
    {
        if (filename == null)
        {
            filenameLabel.setText("No file displayed.");
        }
        else
        {
            filenameLabel.setText("File: " + filename);
        }
    }

    private void showStatus(String text)
    {
        statusLabel.setText(text);
    }

    private void makeFrame()
    {
        frame = new JFrame("ImageViewer");
        makeMenuBar(frame);
        Container contentPane = frame.getContentPane();
        contentPane.setLayout(new BorderLayout(6, 6));
        filenameLabel = new JLabel();
        contentPane.add(filenameLabel, BorderLayout.NORTH);
        imagePanel = new ImagePanel();
        contentPane.add(imagePanel, BorderLayout.CENTER);
        statusLabel = new JLabel(VERSION);
        contentPane.add(statusLabel, BorderLayout.SOUTH);
        showFilename(null);
        frame.pack();
        Dimension d = Toolkit.getDefaultToolkit().getScreenSize();
        frame.setLocation(d.width / 2 - frame.getWidth() / 2, d.height / 2 - frame.getHeight() / 2);
        frame.setVisible(true);
    }

    private void makeMenuBar(JFrame frame)
    {
        final int SHORTCUT_MASK = Toolkit.getDefaultToolkit().getMenuShortcutKeyMask();
        JMenuBar menubar = new JMenuBar();
        frame.setJMenuBar(menubar);
        JMenu menu;
        JMenuItem item;
        menu = new JMenu("File");
        menubar.add(menu);
        item = new JMenuItem("Open");
        item.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_O, SHORTCUT_MASK));
        item.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent e)
            {
                openFile();
            }
        });
        menu.add(item);
        item = new JMenuItem("Close");
        item.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_W, SHORTCUT_MASK));
        item.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent e)
            {
                close();
            }
        });
        menu.add(item);
        menu.addSeparator();
        item = new JMenuItem("Quit");
        item.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_Q, SHORTCUT_MASK));
        item.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent e)
            {
                quit();
            }
        });
        menu.add(item);
        menu = new JMenu("Filter");
        menubar.add(menu);
        item = new JMenuItem("Darker");
        item.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent e)
            {
                makeDarker();
            }
        });
        menu.add(item);
        item = new JMenuItem("Lighter");
        item.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent e)
            {
                makeLighter();
            }
        });
        menu.add(item);
        item = new JMenuItem("Threshold");
        item.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent e)
            {
                threshold();
            }
        });
        menu.add(item);
        menu = new JMenu("Help");
        menubar.add(menu);
        item = new JMenuItem("About ImageViewer...");
        item.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent e)
            {
                showAbout();
            }
        });
        menu.add(item);
    }
}