ImageViewer dengan BlueJ?! - Project di e-book

Hari ini saya belajar tentang GUI. GUI adalah singkatan dari Graphical User Interface. GUI merupakan desain aplikasi dengan tampilan visual sehingga pengguna dapat dengan mudah menggunakan aplikasi. Hari ini, saya mempelajari project ImageViewer versi 1.0. Berikut adalah program tersebut.

Tampilan

Source Code

OFImage

 import java.awt.*;  
 import java.awt.image.*;  
 import javax.swing.*;  
 /**  
  * OFImage is a class that defines an image in OF (Objects First) format.  
  *   
  * @author Michael Kolling and David J. Barnes  
  * @version 1.1  
  */  
 public class OFImage extends BufferedImage  
 {  
   /**  
    * Create an OFImage copied from a BufferedImage.  
    * @param image The image to copy.  
    */  
   public OFImage(BufferedImage image)  
   {  
      super(image.getColorModel(), image.copyData(null),   
         image.isAlphaPremultiplied(), null);  
   }  
   /**  
    * Create an OFImage with specified size and unspecified content.  
    * @param width The width of the image.  
    * @param height The height of the image.  
    */  
   public OFImage(int width, int height)  
   {  
     super(width, height, TYPE_INT_RGB);  
   }  
   /**  
    * Set a given pixel of this image to a specified color. The  
    * color is represented as an (r,g,b) value.  
    * @param x The x position of the pixel.  
    * @param y The y position of the pixel.  
    * @param col The color of the pixel.  
    */  
   public void setPixel(int x, int y, Color col)  
   {  
     int pixel = col.getRGB();  
     setRGB(x, y, pixel);  
   }  
   /**  
    * Get the color value at a specified pixel position.  
    * @param x The x position of the pixel.  
    * @param y The y position of the pixel.  
    * @return The color of the pixel at the given position.  
    */  
   public Color getPixel(int x, int y)  
   {  
     int pixel = getRGB(x, y);  
     return new Color(pixel);  
   }  
   /**  
    * Make this image a bit darker.  
    */  
   public void darker()  
   {  
     int height = getHeight();  
     int width = getWidth();  
     for(int y = 0; y < height; y++) {  
       for(int x = 0; x < width; x++) {  
         setPixel(x, y, getPixel(x, y).darker());  
       }  
     }  
   }  
   /**  
    * Make this image a bit lighter.  
    */  
   public void lighter()  
   {  
     int height = getHeight();  
     int width = getWidth();  
     for(int y = 0; y < height; y++) {  
       for(int x = 0; x < width; x++) {  
         setPixel(x, y, getPixel(x, y).brighter());  
       }  
     }  
   }  
   /**  
    * Perform a three level threshold operation.  
    * That is: repaint the image with only three color values:  
    *     white, gray, and black.  
    */  
   public void threshold()  
   {  
     int height = getHeight();  
     int width = getWidth();  
     for(int y = 0; y < height; y++) {  
       for(int x = 0; x < width; x++) {  
         Color pixel = getPixel(x, y);  
         int brightness = (pixel.getRed() + pixel.getBlue() + pixel.getGreen()) / 3;  
         if(brightness <= 85) {  
           setPixel(x, y, Color.BLACK);  
         }  
         else if(brightness <= 170) {  
           setPixel(x, y, Color.GRAY);  
         }  
         else {  
           setPixel(x, y, Color.WHITE);  
         }  
       }  
     }  
   }  
 }  

ImagePanel

 import java.awt.*;  
 import javax.swing.*;  
 import java.awt.image.*;  
 /**  
  * An ImagePanel is a Swing component that can display an OFImage.  
  * It is constructed as a subclass of JComponent with the added functionality  
  * of setting an OFImage that will be displayed on the surface of this  
  * component.  
  *   
  * @author Michael Kolling and David J. Barnes  
  * @version 1.0  
  */  
 public class ImagePanel extends JComponent  
 {  
   // The current width and height of this panel  
   private int width, height;  
   // An internal image buffer that is used for painting. For  
   // actual display, this image buffer is then copied to screen.  
   private OFImage panelImage;  
   /**  
    * Create a new, empty ImagePanel.  
    */  
   public ImagePanel()  
   {  
     width = 360;  // arbitrary size for empty panel  
     height = 240;  
     panelImage = null;  
   }  
   /**  
    * Set the image that this panel should show.  
    *   
    * @param image The image to be displayed.  
    */  
   public void setImage(OFImage image)  
   {  
     if(image != null) {  
       width = image.getWidth();  
       height = image.getHeight();  
       panelImage = image;  
       repaint();  
     }  
   }  
   /**  
    * Clear the image on this panel.  
    */  
   public void clearImage()  
   {  
     Graphics imageGraphics = panelImage.getGraphics();  
     imageGraphics.setColor(Color.LIGHT_GRAY);  
     imageGraphics.fillRect(0, 0, width, height);  
     repaint();  
   }  
   // The following methods are redefinitions of methods  
   // inherited from superclasses.  
   /**  
    * Tell the layout manager how big we would like to be.  
    * (This method gets called by layout managers for placing  
    * the components.)  
    *   
    * @return The preferred dimension for this component.  
    */  
   public Dimension getPreferredSize()  
   {  
     return new Dimension(width, height);  
   }  
   /**  
    * This component needs to be redisplayed. Copy the internal image   
    * to screen. (This method gets called by the Swing screen painter   
    * every time it want this component displayed.)  
    *   
    * @param g The graphics context that can be used to draw on this component.  
    */  
   public void paintComponent(Graphics g)  
   {  
     Dimension size = getSize();  
     g.clearRect(0, 0, size.width, size.height);  
     if(panelImage != null) {  
       g.drawImage(panelImage, 0, 0, null);  
     }  
   }  
 }  

ImageFileManager

 import java.awt.image.*;  
 import javax.imageio.*;  
 import java.io.*;  
 /**  
  * ImageFileManager is a small utility class with static methods to load  
  * and save images.  
  *   
  * The files on disk can be in JPG or PNG image format. For files written  
  * by this class, the format is determined by the constant IMAGE_FORMAT.  
  *   
  * @author Michael Kolling and David J Barnes   
  * @version 2.0  
  */  
 public class ImageFileManager  
 {  
   // A constant for the image format that this writer uses for writing.  
   // Available formats are "jpg" and "png".  
   private static final String IMAGE_FORMAT = "jpg";  
   /**  
    * Read an image file from disk and return it as an image. This method  
    * can read JPG and PNG file formats. In case of any problem (e.g the file   
    * does not exist, is in an undecodable format, or any other read error)   
    * this method returns null.  
    *   
    * @param imageFile The image file to be loaded.  
    * @return      The image object or null is it could not be read.  
    */  
   public static OFImage loadImage(File imageFile)  
   {  
     try {  
       BufferedImage image = ImageIO.read(imageFile);  
       if(image == null || (image.getWidth(null) < 0)) {  
         // we could not load the image - probably invalid file format  
         return null;  
       }  
       return new OFImage(image);  
     }  
     catch(IOException exc) {  
       return null;  
     }  
   }  
   /**  
    * Write an image file to disk. The file format is JPG. In case of any   
    * problem the method just silently returns.  
    *   
    * @param image The image to be saved.  
    * @param file  The file to save to.  
    */  
   public static void saveImage(OFImage image, File file)  
   {  
     try {  
       ImageIO.write(image, IMAGE_FORMAT, file);  
     }  
     catch(IOException exc) {  
       return;  
     }  
   }  
 }  

ImageViewer

 import java.awt.*;  
 import java.awt.event.*;  
 import java.awt.image.*;  
 import javax.swing.*;  
 import java.io.File;  
 /**  
  * ImageViewer is the main class of the image viewer application. It builds and  
  * displays the application GUI and initialises all other components.  
  *   
  * To start the application, create an object of this class.  
  *   
  * @author Michael Kolling and David J Barnes   
  * @version 1.0  
  */  
 public class ImageViewer  
 {  
   // static fields:  
   private static final String VERSION = "Version 1.0";  
   private static JFileChooser fileChooser = new JFileChooser(System.getProperty("user.dir"));  
   // fields:  
   private JFrame frame;  
   private ImagePanel imagePanel;  
   private JLabel filenameLabel;  
   private JLabel statusLabel;  
   private OFImage currentImage;  
   /**  
    * Create an ImageViewer show it on screen.  
    */  
   public ImageViewer()  
   {  
     currentImage = null;  
     makeFrame();  
   }  
   // ---- implementation of menu functions ----  
   /**  
    * Open function: open a file chooser to select a new image file.  
    */  
   private void openFile()  
   {  
     int returnVal = fileChooser.showOpenDialog(frame);  
     if(returnVal != JFileChooser.APPROVE_OPTION) {  
       return; // cancelled  
     }  
     File selectedFile = fileChooser.getSelectedFile();  
     currentImage = ImageFileManager.loadImage(selectedFile);  
     if(currentImage == null) {  // image file was not a valid image  
       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();  
   }  
   /**  
    * Close function: close the current image.  
    */  
   private void close()  
   {  
     currentImage = null;  
     imagePanel.clearImage();  
     showFilename(null);  
   }  
   /**  
    * Quit function: quit the application.  
    */  
   private void quit()  
   {  
     System.exit(0);  
   }  
   /**  
    * 'Darker' function: make the picture darker.  
    */  
   private void makeDarker()  
   {  
     if(currentImage != null) {  
       currentImage.darker();  
       frame.repaint();  
       showStatus("Applied: darker");  
     }  
     else {  
       showStatus("No image loaded.");  
     }  
   }  
   /**  
    * 'Lighter' function: make the picture lighter  
    */  
   private void makeLighter()  
   {  
     if(currentImage != null) {  
       currentImage.lighter();  
       frame.repaint();  
       showStatus("Applied: lighter");  
     }  
     else {  
       showStatus("No image loaded.");  
     }  
   }  
   /**  
    * 'threshold' function: apply the threshold filter  
    */  
   private void threshold()  
   {  
     if(currentImage != null) {  
       currentImage.threshold();  
       frame.repaint();  
       showStatus("Applied: threshold");  
     }  
     else {  
       showStatus("No image loaded.");  
     }  
   }  
   /**  
    * 'Lighter' function: make the picture lighter  
    */  
   private void showAbout()  
   {  
     JOptionPane.showMessageDialog(frame,   
           "ImageViewer\n" + VERSION,  
           "About ImageViewer",   
           JOptionPane.INFORMATION_MESSAGE);  
   }  
   // ---- support methods ----  
   /**  
    * Display a file name on the appropriate label.  
    * @param filename The file name to be displayed.  
    */  
   private void showFilename(String filename)  
   {  
     if(filename == null) {  
       filenameLabel.setText("No file displayed.");  
     }  
     else {  
       filenameLabel.setText("File: " + filename);  
     }  
   }  
   /**  
    * Display a status message in the frame's status bar.  
    * @param text The status message to be displayed.  
    */  
   private void showStatus(String text)  
   {  
     statusLabel.setText(text);  
   }  
   // ---- swing stuff to build the frame and all its components ----  
   /**  
    * Create the Swing frame and its content.  
    */  
   private void makeFrame()  
   {  
     frame = new JFrame("ImageViewer");  
     makeMenuBar(frame);  
     Container contentPane = frame.getContentPane();  
     // Specify the layout manager with nice spacing  
     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);  
     // building is done - arrange the components and show      
     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);  
   }  
   /**  
    * Create the main frame's menu bar.  
    * @param frame  The frame that the menu bar should be added to.  
    */  
   private void makeMenuBar(JFrame frame)  
   {  
     final int SHORTCUT_MASK =  
       Toolkit.getDefaultToolkit().getMenuShortcutKeyMask();  
     JMenuBar menubar = new JMenuBar();  
     frame.setJMenuBar(menubar);  
     JMenu menu;  
     JMenuItem item;  
     // create the File menu  
     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);  
     // create the Filter menu  
     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);  
     // create the Help menu  
     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);  
   }  
 }