Description

The purpose of the assignment is to write a Java class that can be called by a user interface program to unscramble images in the Portable GreyMap (PGM) format. To do this you need to write an object called Transform that inherits from an interface and implements all methods in that interface. It also instantiates and calls methods in PictureLibrary.java, and is in turn called from a graphical user interface (GUI) class called ImageProgram.java. Both of these are supplied below.

Instructions

Part One

Create a new project P8 and a class called Transforms, without a main method. Note: You may want to leverage code from the R11 recitation.

Download and import PictureLibrary.java

Download and import ImageProgram.java

Download and import ImageInterface.java

Make the class implement the ImageInterface interface, as shown in the lab and discussed in class.

Do NOT modify any of the given files, just import them into your P8 src folder

Part Two

At the top of the class, declare the following instance (non-static) variables:

An object of type PictureLibrary, set to null.

An integer to store the image width, set to 0.

An integer to store the image height, set to 0.

A 2-dimensional array of integers to store the image data, not allocated.

Name your variables whatever you want

Create a constructor for the Transforms class as shown below that instantiates an object of type PictureLibrary into the associated class instance variable.

 public Transforms(){ //Instantiate PictureLibrary object } 

Part Three

Implement the methods in the ImageInterface interface. All methods need to be created before your code will compile. The readImagemethod should call the readPGM method in the PictureLibrary object, passing the input file name, then it should call the getHeight, getWidth, and getData methods to fill in the class instance data defined above. The writeImage method should call the setData method in the Picture object with the image data, then call the writePGM method passing the output file name. The parameters and return types of the methods in PictureLibrary.java are not documented here, so you must look at the file to find them. The calls to readImage andwriteImage should be wrapped in a try catch block as follows:

try { // Calls to readPGM or writePGM and associated code here } catch (Exception e) { System.out.println(e.getMessage()); } 

Implement imageData by simply returning a copy of the image array. The remaining methods manipulate the image data in some way or another to restore an image that has been scrambled.

Part Four

Make sure that all methods exist in your Transforms.java, even though some of the transformations may not do anything. You should now be able to run the main program in ImageProgram.java to read and write PGM files. If you are having trouble integrating with the provided files, check that your method names and parameters match. We have provided a test file called Cam.pgm that you can download to the P8 project directory (not into the /src or /bin subdirectories).

Part Five

Implement the remaining methods as follows:

Calling decode restores an image in which each pixel has had the upper four bits negated. To unscramble the image, your code should negate them again. You can use bitwise operators or the following algorithm: To get the upper bits, divide the pixel by 16. To get the lower bits, modulo the pixel by 16. The resulting upper and lower values should be in the range 0..15. Negate the upper bits as follows: upper = 15 - upper; Then put the bits back together by multiplying the upper bits by 16 and adding the result to lower. Here's an example for your testing:

original pixel = 115 = 0b01110011

upper value = 115 / 16 = 7 = 0b0111 (upper four bits of original)

lower value = 115 % 16 = 3 = 0b0011 (lower four bits of original)

negate upper value = 15 - 7 = 8 = 0b1000

new pixel = (upper * 16) + lower = (8 * 16) + 3 = 131 = 0b10000011

Calling swap restores an image in which each pixel has been scrambled by exhanging the lower 2 bits with the upper 2 bits. To do this requires that your code do the same exchange to restore the original pixel. Don't modify the middle four bits. By far the easiest way to do this is to use the bitwise operators. Here's an example for your testing:

original pixel = 114 = 0b01110010

upper two bits of original = 0b01110010 & 0b11000000 = 0b01000000

middle four bits of original = 0b01110010 & 0b00111100 = 0b00110000

lower two bits of original = 0b01110010 & 0b00000011 = 0b00000010

new pixel = (lower << 6) | middle | (upper >> 6)

Calling mirror reverses the image top to bottom. To reverse top to bottom, exchange the first row for the last row, the second row for the second to last row, and so on until the entire image is reversed.

Calling exchange swaps the image area defined by a rectangle with width 150 and height 300 starting at row index 10 and column index 10 for a rectangle of the same size starting at row index 10, and column index 310.

NOTE: The maximum value of a pixel (PictureLibrary.MAXVAL) is 255, so only 8 bits are valid for each pixel. These are numbered bits 0-7, where bit 0 is equal to 1 and bit 7 is equal to 128. There are no negative values allowed.

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Picture Library.java

// Picture.java

// Reads and writes .pgm files import java.io.File; import java.io.FileOutputStream; import java.io.IOException; import java.io.PrintStream; import java.util.Scanner; public class PictureLibrary { // Maximum intensity public static final int MAXVAL = 255; // Image data private int[][] image; // Get image height public int getHeight() { return image.length; } // Get image width public int getWidth() { return image[0].length; } // Get image data public int[][] getData() { return image; } // Set image data public void setData(int[][] data) { image = data; } // Read PGM file public void readPGM(String path) throws Exception { int width; int height; int maxval; try { Scanner in = new Scanner(new File(path)); String magic = in.next(); if (!magic.equals("P2")) { in.close(); throw new Exception("ERROR: cannot read .pgm file " + path); } width = in.nextInt(); height = in.nextInt(); maxval = in.nextInt(); image = new int[height][width]; for (int y = 0; y < height; y++) for (int x = 0; x < width; x++) image[y][x] = in.nextInt(); in.close(); } catch (IOException e) { throw new Exception("ERROR: cannot read .pgm file " + path); } // Scale values to the range 0-MAXVAL if (maxval != MAXVAL) for (int j = 0; j < height; j++) for (int i = 0; i < width; i++) image[j][i] = (image[j][i] * MAXVAL) / maxval; return; } // Write PGM file public void writePGM(String path) throws Exception { int height = getHeight(); int width = getWidth(); try { PrintStream output = new PrintStream(new FileOutputStream(path)); output.println("P2"); output.println(width + " " + height); output.println(MAXVAL); for (int row = 0; row < height; row++) for (int col = 0; col < width; col++) output.println(image[row][col]); // One pixel per line! output.close(); } catch (IOException e) { throw new Exception("ERROR: cannot write .pgm file " + path); } } } 

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Image Program.java

// ImageProgram.java // User interface for image manipulation import java.awt.*; import java.awt.event.*; import java.awt.image.*; import java.io.*; import javax.swing.*; public class ImageProgram extends JFrame implements ActionListener { private static final long serialVersionUID = 1L; // get rid of warning // Program flags private boolean mIsInitialized; // GUI initialized? private boolean mIsDirty; // image modified? // Menu items private JMenuItem mOpenFile; private JMenuItem mSaveFile; private JMenuItem mExitCommand; private JMenuItem mDecode; private JMenuItem mSwap; private JMenuItem mMirror; private JMenuItem mExchange; private JLabel mLabel; // Transforms object from student private ImageInterface mStudent; // Array and static code are used to convert a gray scale to RGB private static int[] pgm2RGB; static { pgm2RGB = new int[256]; for (int i = 0; i < 256; i++) { pgm2RGB[i] = (255 << 24) | (i << 16) | (i << 8) | i; } } // Constructor. Note that very little initialization is done here. // Since a derived class may override some of the initialization methods // these methods should NOT be called from a constructor because routines // in the derived class could be executed before the constructor of the super // class completes. In general, all code in the super class constructor // should be executed before ANY code in the derived class is executed. public ImageProgram () { super(); setSize(new Dimension(400, 300)); } // Satisfy the ActionListener interface. Most of the work is delegated to // the method doAction(). This allows a derived class to override doAction // (instead of actionPerformed()) and take advantage of the error handling // done here. If a derived class overrides actionPerformed() in may need // to duplicate the error handling. public void actionPerformed (ActionEvent actionEvent) { try { doAction(actionEvent); } catch (Throwable t) { t.printStackTrace(); } } // This can throw exceptions, because they are caught by performAction() // If you derive your own class from this class, and add new menus // or menu items, you would override this method to handle your new // menu items and delegate the work back to this method if the "action" // is not one of those you defined in your derived class. There are many // ways to dispatch from an event to the underlying code. This illustrates // one simple way of doing that. protected void doAction (ActionEvent actionEvent) throws Exception { Object src = actionEvent.getSource(); if (src == mOpenFile) openFile(); else if (src == mSaveFile) saveFile(); else if (src == mExitCommand) exitGUI(); else if (src == mDecode) decode(); else if (src == mSwap) swap(); else if (src == mMirror) mirror(); else if (src == mExchange) exchange(); } // Override setVisible() to initialize everything the first time the // component becomes visible public void setVisible (boolean visible) { if (visible) { if (! mIsInitialized) { startGUI(); mIsInitialized = true; } } super.setVisible(visible); } // Build the GUI. protected void startGUI() { setJMenuBar(makeMenuBar()); addWindowListener(new WindowAdapter() { public void windowClosing (WindowEvent we) { mExitCommand.doClick(); // Press the Exit menu item } }); getContentPane().add(makeMainPanel()); } // Exit the GUI private void exitGUI() { if (mIsDirty) { if (!getYesNo("Data has not been saved.", "Continue?")) return; } System.exit(0); } // Creates the main panel of the GUI protected JPanel makeMainPanel() { JPanel panel = new JPanel(new BorderLayout()); mLabel = new JLabel(); panel.add(mLabel, BorderLayout.CENTER); return panel; } // Created the menu bar for the GUI. Delegates most of the work to // methods which create the individual menus. The "adds" should remind you // of your work with ArrayLists. A JMenuBar is conceptually just a list of // menus. You will find methods on a JMenuBar to manipulate the elements // of the list. protected JMenuBar makeMenuBar() { JMenuBar mb = new JMenuBar(); mb.add(makeFileMenu()); mb.add(makeActionMenu()); return mb; } // Create the file menu. Again, the "adds" (see makeMeniItem)should remind you // of list manipulation. A JMenu is conceptually a list of JMenuItems. // Interestingly, a JMenu is a JMenuItem. Why do you think that is?? protected JMenu makeFileMenu() { JMenu menu = makeMenu("File", 'F'); mOpenFile = makeMenuItem(menu, "Open...", 'O'); mSaveFile = makeMenuItem(menu, "Save...", 'S'); mExitCommand = makeMenuItem(menu, "Exit", 'X'); return menu; } // Create the action menu. protected JMenu makeActionMenu() { JMenu menu = makeMenu("Action", 'A'); mDecode = makeMenuItem(menu, "Decode" , 'D'); mSwap = makeMenuItem(menu, "Swap" , 'S'); mMirror = makeMenuItem(menu, "Mirror" , 'M'); mExchange = makeMenuItem(menu, "Exchange" , 'E'); return menu; } // Convenience method for making JMenu protected JMenu makeMenu (String name, char mnemonic) { JMenu menu = new JMenu(name); menu.setMnemonic(mnemonic); return menu; } // Convenience method for making JMenuItem protected JMenuItem makeMenuItem (String name, char mnemonic) { JMenuItem mi = new JMenuItem(name, (int) mnemonic); mi.addActionListener(this); return mi; } // Convenience method for putting JMenuItem in a menu protected JMenuItem makeMenuItem (JMenu menu, String name, char mnemonic) { JMenuItem mi = makeMenuItem(name, mnemonic); menu.add(mi); return mi; } // Convenience method to get yes/no from user protected boolean getYesNo (String title, String message) { int answer = JOptionPane.showInternalConfirmDialog(getContentPane(), message, title, JOptionPane.YES_NO_OPTION, JOptionPane.WARNING_MESSAGE); return (answer == JOptionPane.YES_OPTION); } // Open image file private void openFile() throws Exception { // Data saved? if (mIsDirty) { if (!getYesNo("Open file", "Data has not been saved. Continue?")) return; } String fileName = selectFile("Select file to open", true); if (fileName != null) { mStudent = new Transforms(); mStudent.readImage(fileName); resetImage(); mIsDirty = false; } } // Save image file private void saveFile() throws Exception { String fileName = selectFile("Select file name to save", false); if (fileName != null) { mStudent.writeImage(fileName); mIsDirty = false; } } // Other student methods private void decode() { if (mStudent != null) { mStudent.decode(); resetImage(); } } private void swap() { if (mStudent != null) { mStudent.swap(); resetImage(); } } private void mirror() { if (mStudent != null) { mStudent.mirror(); resetImage(); } } private void exchange() { if (mStudent != null) { mStudent.exchange(); resetImage(); } } // File selector private String selectFile (String title, boolean open) { String fileName = null; JFileChooser jfc = new JFileChooser(); jfc.setCurrentDirectory(new File(".")); jfc.setDialogTitle(title); int result; if (open) result = jfc.showOpenDialog(this); else result = jfc.showSaveDialog(this); if (result == JFileChooser.APPROVE_OPTION) { File file = jfc.getSelectedFile(); fileName = file.getAbsolutePath(); } return fileName; } // Reset image private void resetImage() { if (mStudent != null) { // Copy the pixel values int image[][] = mStudent.imageData(); int rows = image.length; int cols = image[0].length; BufferedImage buffer = new BufferedImage(cols, rows, BufferedImage.TYPE_INT_ARGB); for (int row = 0; row < rows; row++) { for (int col=0; col < cols; col++) { int rgb = pgm2RGB[image[row][col]]; buffer.setRGB(col, row, rgb); } } ImageIcon imageIcon = new ImageIcon(buffer); mLabel.setIcon(imageIcon); mIsDirty = true; pack(); // make window just fit image } } // Main program public static void main (String[] args) throws IOException { ImageProgram gui = new ImageProgram(); gui.setVisible(true); } } 

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Image Interface.java

// ImageInterface.java // Interface for imaging program public interface ImageInterface { // Read the image public void readImage(String inFile); // Write the image public void writeImage(String outFile); // Get image data public int[][] imageData(); // Decode the pixels public void decode(); // Swap the nibbles in each pixel public void swap(); // Mirror the image corner to corner public void mirror(); // Exchange two rectangles in image public void exchange(); }