Below is the syntax highlighted version of Picture.java
from § Standard Libraries.
Here is the Javadoc.
/************************************************************************* * Compilation: javac Picture.java * Execution: java Picture filename * * Data type for manipulating individual pixels of an image. The original * image can be read from a file in JPEG, GIF, or PNG format, or the * user can create a blank image of a given size. Includes methods for * displaying the image in a window on the screen or saving to a file. * * % java Picture image.jpg * * Remarks * ------- * - pixel (0, 0) is upper left hand corner * * - see also GrayPicture.java for a grayscale version * *************************************************************************/ import javax.imageio.ImageIO; import javax.swing.JFrame; import javax.swing.JMenu; import javax.swing.JMenuBar; import javax.swing.JLabel; import javax.swing.JMenuItem; import javax.swing.ImageIcon; import javax.swing.KeyStroke; import java.awt.FileDialog; import java.awt.Toolkit; import java.awt.Color; import java.awt.image.BufferedImage; import java.awt.event.ActionListener; import java.awt.event.ActionEvent; import java.awt.event.KeyEvent; import java.io.File; import java.io.IOException; import java.net.URL; /** * This class provides methods for manipulating individual pixels of * an image. The original image can be read from a file in JPEG, GIF, * or PNG format, or the user can create a blank image of a given size. * This class includes methods for displaying the image in a window on * the screen or saving to a file. * <p> * For additional documentation, see * <a href="http://www.cs.princeton.edu/introcs/31datatype">Section 3.1</a> of * <i>Introduction to Programming in Java: An Interdisciplinary Approach</i> * by Robert Sedgewick and Kevin Wayne. */ public final class Picture implements ActionListener { private BufferedImage image; // the rasterized image private JFrame frame; // on-screen view private String filename; // name of file /** * Create an empty w-by-h picture. */ public Picture(int w, int h) { image = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB); // set to TYPE_INT_ARGB to support transparency filename = w + "-by-" + h; } /** * Create a picture by reading in a .png, .gif, or .jpg from * the given filename or URL name. */ public Picture(String filename) { this.filename = filename; try { // try to read from file in working directory File file = new File(filename); if (file.isFile()) { image = ImageIO.read(file); } // now try to read from file in same directory as this .class file else { URL url = getClass().getResource(filename); if (url == null) { url = new URL(filename); } image = ImageIO.read(url); } } catch (IOException e) { // e.printStackTrace(); throw new RuntimeException("Could not open file: " + filename); } // check that image was read in if (image == null) { throw new RuntimeException("Invalid image file: " + filename); } } /** * Create a picture by reading in a .png, .gif, or .jpg from a File. */ public Picture(File file) { try { image = ImageIO.read(file); } catch (IOException e) { e.printStackTrace(); throw new RuntimeException("Could not open file: " + file); } if (image == null) { throw new RuntimeException("Invalid image file: " + file); } } /** * Return a JLabel containing this Picture, for embedding in a JPanel, * JFrame or other GUI widget. */ public JLabel getJLabel() { if (image == null) { return null; } // no image available ImageIcon icon = new ImageIcon(image); return new JLabel(icon); } /** * Display the picture in a window on the screen. */ public void show() { // create the GUI for viewing the image if needed if (frame == null) { frame = new JFrame(); JMenuBar menuBar = new JMenuBar(); JMenu menu = new JMenu("File"); menuBar.add(menu); JMenuItem menuItem1 = new JMenuItem(" Save... "); menuItem1.addActionListener(this); menuItem1.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_S, Toolkit.getDefaultToolkit().getMenuShortcutKeyMask())); menu.add(menuItem1); frame.setJMenuBar(menuBar); frame.setContentPane(getJLabel()); // f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE); frame.setTitle(filename); frame.setResizable(false); frame.pack(); frame.setVisible(true); } // draw frame.repaint(); } /** * Return the height of the picture (in pixels). */ public int height() { return image.getHeight(null); } /** * Return the width of the picture (in pixels). */ public int width() { return image.getWidth(null); } /** * Return the Color of pixel (i, j). */ public Color get(int i, int j) { return new Color(image.getRGB(i, j)); } /** * Set the Color of pixel (i, j) to c. */ public void set(int i, int j, Color c) { if (c == null) { throw new RuntimeException("can't set Color to null"); } image.setRGB(i, j, c.getRGB()); } /** * Save the picture to a file in a standard image format. * The filetype must be .png or .jpg. */ public void save(String name) { save(new File(name)); } /** * Save the picture to a file in a standard image format. */ public void save(File file) { this.filename = file.getName(); if (frame != null) { frame.setTitle(filename); } String suffix = filename.substring(filename.lastIndexOf('.') + 1); suffix = suffix.toLowerCase(); if (suffix.equals("jpg") || suffix.equals("png")) { try { ImageIO.write(image, suffix, file); } catch (IOException e) { e.printStackTrace(); } } else { System.out.println("Error: filename must end in .jpg or .png"); } } /** * Opens a save dialog box when the user selects "Save As" from the menu. */ public void actionPerformed(ActionEvent e) { FileDialog chooser = new FileDialog(frame, "Use a .png or .jpg extension", FileDialog.SAVE); chooser.setVisible(true); if (chooser.getFile() != null) { save(chooser.getDirectory() + File.separator + chooser.getFile()); } } /** * Test client. Reads a picture specified by the command-line argument, * and shows it in a window on the screen. */ public static void main(String[] args) { Picture pic = new Picture(args[0]); pic.show(); } }