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## Solution for Programming Exercise 13.2

This page contains a sample solution to one of the exercises from Introduction to Programming Using Java.

### Exercise 13.2:

For this exercise, you should continue to work on the program from the previous exercise. Add a "StrokeWidth" menu that allows the user to draw lines of varying thicknesses. Make it possible to use different colors for the interior of a filled shape and for the outline of that shape. To do this, change the "Color" menu to "StrokeColor" and add a "FillColor" menu. (My solution adds two new tools, "Stroked Filled Rectangle" and "Stroked Filled Oval", to represent filled shapes that are outlined with the current stroke.) Add support for filling shapes with transparent color. A simple approach to this is to use a JCheckboxMenuItem to select either fully opaque or 50% opaque fill. (Don't try to apply transparency to stokes -- it's very difficult to make transparency work correctly for the Curve tool, and in any case, shape outlines look better if they are opaque.) Finally, make the menus more user friendly by adding keyboard accelerators to some commands and by using JRadioButtonMenuItems where appropriate, such as in the color and tool menus. This exercise takes quite a bit of work to get it all right, so you should tackle the problem in pieces.

Discussion

Most of the individual things that you have to do for this exercise are not very difficult, but there are a lot of them. First of all, although it was not required by the project, I decided to use antialiasing, since it produces nicer pictures. So, before drawing in a graphics context g, I say

    Graphics2D g2 = (Graphics2D)g;
    g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                          RenderingHints.VALUE_ANTIALIAS_ON);

I added these lines at several points in the program, both for the graphics context in the paintComponent() method and for graphics contexts for drawing in the off-screen canvas.

There are a lot of changes in the getMenuBar() method, which creates the menus that are used in the program. First of all, I changed the colorMenu to strokeColorMenu, and I added two new menus named strokeWidthMenu and fillColorMenu. The contents of the strokeColorMenu are the same as the old colorMenu, but the items in that menu have changed from simple JMenuItems to JRadioButtonMenuItems. All the items are added to the same ButtonGroup so that only one of the items in the menu can be selected. The only real point of this is to give the user some visual feedback about which color is currently selected in the menu -- this is just the sort of touch that can make a program much more usable. Items could be added to the menu as follows:

    ButtonGroup group = new ButtonGroup();  // Will contain all the radio buttons.

    JRadioButtonMenuItem radioItem;
    radioItem = new JRadioButtonMenuItem("Draw With Black");
    strokeColorMenu.add( radioItem );
    group.add( radioItem );
    radioItem.setSelected( true );  // Black is currently selected.
    radioItem.addActionListener( listener );

    JRadioButtonMenuItem radioItem;
    radioItem = new JRadioButtonMenuItem("Draw With White");
    strokeColorMenu.add( radioItem );
    group.add( radioItem );
    radioItem.addActionListener( listener );
       .
       .
       .

However, having so much repetitive code becomes annoying, so I decided to write a method to do the work. The method makes an entire set of JRadioButtonMenuItems and adds them to a menu. I pass the names of all the menu items to the method as an array of Strings. My first version of this method looked like this:

    /**
     * Adds a set of JRadioButtonMenuItems to a JMenu.  All the items are in
     * the same button group and have the same ActionListener.  Initially,
     * the first item is selected.
     * @param menu  the menu to which the items will be added
     * @param commandNames  the names of the items
     * @param listener  the ActionListener for the items
     */
    private void createRadioGroup(JMenu menu, String[] commandNames,
                                                    ActionListener listener) {
       ButtonGroup group = new ButtonGroup();
       for ( int i = 0; i < commandNames.length; i++ )  {
          JRadioButtonMenuItem item = new JRadioButtonMenuItem(commandNames[i]);
          menu.add(item);
          group.add(item);
          if ( i == 0 ) // First item is the one that is currently selected.
             item.setSelected(true);
       }
    }

With this method available, I could fill the strokeColorMenu with one command:

    createRadioGroup( strokeColorMenu,
          new String[] {
             "Draw With Black", "Draw With White", "Draw With Red",
             "Draw With Green", "Draw With Blue", "Draw With Yellow",
             "Custom Drawing Color..."
          }, listener);

I also used createRadioGroup() to add entries to fillColorMenu and strokeWidthMenu. When I came to the toolMenu, I wanted to add separators between some of the menu items, but the createRadioGroup() method just adds all the items to the menu, without separators. To solve this problem, I came up with the idea of using a null value in the array of commandNames to indicate a position where a separator should be inserted instead of a menu item.

It was not until the end of the project that I added accelerator keys to the menus. Once again, my createRadioGroup() caused a problem, since it provided no way to add accelerator keys to the menu items that it creates. At first, this stumped me, and I thought I might have to go back to creating individual menu items. However, I came up with the idea of coding the accelerator key into the command name in the commandName array. For example, to specify the accelerator keystroke "ctrl L" for the "Line" command, I used "Line/ctrl L" in the array. The final version of the createRadioGroup() method became:

    /**
     * Adds a set of JRadioButtonMenuItems to a JMenu.  All the items are in
     * the same button group and have the same ActionListener.
     * @param menu  the menu to which the items will be added
     * @param commandNames  the names of the items; null values in this array
     *    become separators in the menu.  The name can contain the character "/".
     *    In that case the actual item name is the part of the name that
     *    precedes the "/" and the remainder of the name specifies a
     *    KeyStroke that will be used as the keyboard accelerator key
     *    for the item.
     * @param listener  the ActionListener for the items
     */
    private void createRadioGroup(JMenu menu, String[] commandNames,
                                                    ActionListener listener) {
       ButtonGroup group = new ButtonGroup();
       for ( int i = 0; i < commandNames.length; i++) {
          if (commandNames[i] == null)
             menu.addSeparator();
          else {
             String name = commandNames[i];
             String accel = null;
             if (name.indexOf("/") > 0) {
                int pos = name.indexOf("/");  // Extract accelerator key and name.
                accel = name.substring(pos+1);
                name = name.substring(0,pos);
             }
             JRadioButtonMenuItem item = new JRadioButtonMenuItem(name);
             menu.add(item);
             group.add(item);
             item.addActionListener(listener);
             if (accel != null)
                item.setAccelerator(KeyStroke.getKeyStroke(accel));
             if (i == 0)
                item.setSelected(true);
          }
       }
    }

With this method available, I could fill the "Tool" menu with:

    createRadioGroup( toolMenu,
          new String[] {
             "Curve/ctrl U", null, "Line/ctrl L", "Rectangle/ctrl R", "Oval/ctrl V",
             "Filled Rectangle/ctrl alt R", "Filled Oval/ctrl alt V",
             "Stroked Filled Rectangle/ctrl shift R", "Stroked Filled Oval/ctrl shift V",
             null, "Smudge/ctrl M", "Erase/ctrl E"
          }, listener);

The only other menu command that remains to be added is the one that controls transparency. For that, I needed a JCheckBoxMenuItem. Whenever a filled shape is drawn, the setting of this item has to be checked to determine whether or not to use a transparent color. Since I need to have the item available for use in more than one method, it's an instance variable in the class:

    private JCheckBoxMenuItem transparent = new JCheckBoxMenuItem("Translucent Fill");

I decided to add this item to the end of the "FillColor" menu, since it only affects colors that are used for filling shapes.

The new menu commands had to be implemented in the actionPerformed() method that responds when the user selects a menu command. This was straightforward. I did have to introduce a new instance variable to represent the fill color, since previously there was only a single color, used for both filling and drawing. Note that no response is programmed for the JCheckBoxMenuItem, transparent, since the program can check the status of the checkbox itself whenever it needs to know the status.

Turning to the implementation of all the new menu commands, consider the problem of setting the properties of a graphics context before drawing. Previously, it was just a matter of setting a color. Now, there is the possibility of using transparency (when filling a shape) or using a non-default BasicStroke (when drawing a line or outlining a shape). To make it easier to take these possibilities into account, I wrote the following two methods:

    /**
     * Set the graphics context g to use the current stroke color and
     * lineWidth.
     */
    private void applyStrokeProperties(Graphics g) {
       if (lineWidth > 1) {
          Graphics2D g2 = (Graphics2D)g;
          g2.setStroke( new BasicStroke(lineWidth,
                                BasicStroke.CAP_ROUND, BasicStroke.JOIN_MITER) );
       }
       g.setColor(currentStrokeColor);
    }

    /**
     * Set the graphics context g to use the current fill color, taking
     * into account the setting of transparency.  If transparency is on,
     * the RGB components are obtained from the current fill color, and
     * the alpha component is set to 125.
     */
    private void applyFillColor(Graphics g) {
       Color c = currentFillColor;
       if (transparent.isSelected())
          g.setColor(new Color( c.getRed(), c.getGreen(), c.getBlue(), 125 ));
       else
          g.setColor(c);
    }

I used BasicStroke.CAP_ROUND for the BasicStroke because the default cap gave really ugly results when drawing a thick curve. Note that to implement transparency, I just use a transparent version of the current color. The currentColor variable always holds a fully opaque color.

Drawing ovals and rectangles has become more complicated, since there are now three different possibilities for each shape: fill only, outline only, or both fill and outline. To implement this, I modified the putRect() method to have two boolean parameters, one to tell whether to fill the rectangle and one to tell whether to outline it:

    /**
     * Draws a rectangle with corners at the points (x1,y1)
     * and (x2,y2).  Nothing is drawn if x1 == x2 or y1 == y2.  The rectangle
     * can be either stroked (that is, the outline is drawn) or filled or both.
     * @param g the graphics context where the rectangle is drawn
     * @param stroked tells whether to draw an outline of the rectangle.
     * @param filled tells whether to draw a filled or unfilled rectangle.
     */
    private void putRect(Graphics g, boolean stroked, boolean filled,
                                       int x1, int y1, int x2, int y2) {
       if (x1 == x2 || y1 == y2)
          return;
       if (x2 < x1) {  // Swap x1,x2 if necessary to make x2 > x1.
          int temp = x1;
          x1 = x2;
          x2 = temp;
       }
       if (y2 < y1) {  // Swap y1,y2 if necessary to make y2 > y1.
          int temp = y1;
          y1 = y2;
          y2 = temp;
       }
       if (filled) {
          applyFillColor(g);
          g.fillRect(x1,y1,x2-x1,y2-y1);
       }
       if (stroked) {
          applyStrokeProperties(g);
          g.drawRect(x1,y1,x2-x1,y2-y1);
       }
    }

And putOval() was modified in the same way. When I call these methods (in the putShape() method), the value that I used for stroked and filled depend on which tool is currently selected.

There is one further really tricky point. The method repaintRect() is defined to call repaint() for a rectangle with corners (x1,y1) and (x2,y2). I call this method when part of the offscreen canvas is modified, so that that part of the canvas can be copied to the screen. For example, after drawing a rectangle or oval with corners (x1,y1) and (x2,y2), I call repaintRect(x1,y1,x2,y2). The problem is that the drawing operation can actually modify parts of the canvas that are outside the specified rectangle. When you outline the figure with a wide stroke, part of the stroke will lie outside the boundary of the rectangle, and that part will not be copied to the screen. A quick solution would be to simply call repaint() to repaint the entire component. Repainting just a rectangle is an optimization. It's more efficient, but it probably doesn't affect the performance of the program all that much. However, another solution is simply to make the rectangle that is repainted big enough to contain the entire area that was modified in the canvas. That's the approach that I take in my solution.

The Solution

Significant changes from the solution to Exercise 13.1 are shown in red

    import java.awt.*;
    import java.awt.event.*;
    import javax.swing.*;
    import javax.imageio.ImageIO;
    import java.awt.image.BufferedImage;
    import java.io.*;
    import java.util.EnumSet;

    /**
     * An improved paint program with File and undo commands.
     * Note that the way that the off-screen canvas is used
     * in this class requires that the panel be non-resizable; this
     * is because the size of the off-screen canvas does not change
     * when the panel changes size.
     */
    public class PaintWithOSCFinal extends JPanel {

       /**
        * The main routine simply opens a window that shows a PaintWithOSCFinal panel.
        */
       public static void main(String[] args) {
          JFrame window = new JFrame("PaintWithOSCFinal");
          PaintWithOSCFinal content = new PaintWithOSCFinal();
          window.setContentPane(content);
          window.setJMenuBar(content.getMenuBar());
          window.pack();
          window.setResizable(false);
          Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
          window.setLocation( (screenSize.width - window.getWidth())/2,
                (screenSize.height - window.getHeight())/2 );
          window.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
          window.setVisible(true);
       }

       /**
        * The possible drawing tools in this program.  (The CURVE tool allows the
        * user to sketch a free-hand curve, while the LINE tool draws a line
        * between two points.  The SMUDGE tool lets the user "spread paint around"
        * with the mouse.  The ERASE tool erases with a 10-by-10 pixel rectangle.)
        */
       private enum Tool { CURVE, LINE, RECT, OVAL, FILLED_RECT, FILLED_OVAL,
          STROKED_FILLED_RECT, STROKED_FILLED_OVAL, SMUDGE, ERASE }

       /**
        * The set of Tools that represent "shapes."  Shapes are handled differently
        * during dragging than other tools, since they are drawn "on top of" the
        * current picture during a mouse drag and are only added permanently to the
        * picture on mouse release.
        */
       private final static EnumSet<Tool> SHAPE_TOOLS =
                                        EnumSet.range(Tool.LINE, Tool.STROKED_FILLED_OVAL);

       /**
        * The currently selected drawing tool.  Initially Tool.CURVE.  Can be
        * changed by the user with commands in the "Tool" menu.
        */
       private Tool currentTool = Tool.CURVE;

       /**
        * The current drawing color for drawing lines.  Initially Color.BLACK.  Can be
        * changed by the user using the "StrokeColor" menu.
        */
       private Color currentStrokeColor = Color.BLACK;

       /**
        * The current drawing color for filling shapes.  Initially Color.BLACK.  Can be
        * changed by the user using the "FillColor" menu. This is a fully opaque color,
        * even if the user has selected transparent  drawing; transparency is applied when
        * the color is used.
        */
       private Color currentFillColor = Color.BLACK;

       /**
        * The background color that is used to fill the off-screen canvas when
        * it is created.  If the user selects the "Fill With Color", the fill
        * color changes, and the canvas is filled with the new fill color,
        * erasing whatever was there before.
        */
       private Color fillColor = Color.WHITE;

       /**
        * The width of the stroke that is used to draw lines and curves.
        */
       private int lineWidth = 1;

       /**
        * Tells whether to fill shapes with fully opaque colors or to use colors that are
        * 50% transparent.
        */
       private JCheckBoxMenuItem transparent = new JCheckBoxMenuItem("Translucent Fill");

       /**
        * The off-screen canvas.  This is not created until the first time
        * paintComponent() is called.  If the size of the component changes,
        * a new OSC is created (and the picture in the old one is lost).
        */
       private BufferedImage OSC;

       /**
        * This is set to true when the user is dragging the mouse.
        */
       private boolean dragging;

       /**
        * The start position of the mouse during a mouse drag.
        */
       private int startX, startY;

       /**
        * The current position of the mouse during a mouse drag.
        */
       private int currentX, currentY;

       /**
        * File dialog for implementing the File menu commands.
        */
       private JFileChooser fileDialog;

       /**
        * An extra copy of the image that is used for the Undo command.
        * Before any change is made to the image, the image is copied
        * to this variable.  The Undo command swaps the saved image
        * with the image that is shown on screen.  (Thus, a second Undo
        * will effectively act as a Redo.)
        */
       private BufferedImage imageSavedForUndo;

       /**
        * The constructor sets the preferred size of the panel to
        * 640-by-480.  It also sets up a mouse listener.
        */
       public PaintWithOSCFinal() {
          setPreferredSize(new Dimension(640,480));
          MouseHandler mouseHandler = new MouseHandler();
          addMouseListener(mouseHandler);
          addMouseMotionListener(mouseHandler);
       }

       /**
        * The paintComponent() method copies the off-screen canvas to the screen
        * (first creating it, if necessary).  If a mouse drag is in progress,
        * then the current tool is not Tool.CURVE, then the shape that the user
        * is drawing is drawn over the off-screen canvas.  (This is to avoid
        * making the shape a permanent part of the picture until after the user
        * releases the mouse.  The effect is a "rubber band cursor" in which
        * the shape changes as the user drags the mouse, but the picture under
        * the shape is not affected.)
        */
       public void paintComponent(Graphics g) {

          /* First create the off-screen canvas, if it does not already exist. */

          if (OSC == null)
             createOSC();

          /* Copy the off-screen canvas to the panel.  Since we know that the
                image is already completely available, the fourth "ImageObserver"
                parameter to g.drawImage() can be null.  Since the canvas completely
                fills the panel, there is no need to call super.paintComponent(g). */

          g.drawImage(OSC,0,0,null);

          /* If the user is currently dragging the mouse to draw a line, oval,
                or rectangle, draw the shape on top the image from the off-screen
                canvas, using the current drawing color.  (This is not done if the
                user is drawing a curve or using the smudge tool.) */

          if (dragging && SHAPE_TOOLS.contains(currentTool)) {
             Graphics2D g2 = (Graphics2D)g;
             g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                                   RenderingHints.VALUE_ANTIALIAS_ON);
             putCurrentShape(g);
          }

       }

       /**
        * This method creates the off-screen canvas and fills it with the current
        * fill color.  The image that is used to implement the Undo command is
        * also created here.
        */
       private void createOSC() {
          OSC = new BufferedImage(getWidth(),getHeight(),BufferedImage.TYPE_INT_RGB);
          imageSavedForUndo = new BufferedImage(getWidth(),getHeight(),BufferedImage.TYPE_INT_RGB);
          Graphics osg = OSC.createGraphics();
          osg.setColor(fillColor);
          osg.fillRect(0,0,getWidth(),getHeight());
          osg.dispose();
          saveUndoImage();
       }

       /**
        * Copies the current image into the image that is saved for the Undo
        * command.  This method is called before any change is made to the image.
        */
       private void saveUndoImage() {
          Graphics g = imageSavedForUndo.createGraphics();
          g.drawImage(OSC,0,0,null);
          g.dispose();
       }

       /**
        * A utility method to draw the current shape in a given graphics context.
        * It draws the correct shape for the current tool in a rectangle whose
        * corners are given by the starting position of the mouse and the current
        * position of the mouse.  This is used by paintComponent() during a
        * mouse drag.  It is also used to make the shape a permanent part of the
        * off-screen canvas when the mouse is released.
        * This method is not used when the current tool is Tool.CURVE or Tool.SMUDGE.
        */
       private void putCurrentShape(Graphics g) {
          switch (currentTool) {
          case LINE:
             applyStrokeProperties(g);
             g.drawLine(startX, startY, currentX, currentY);
             break;
          case OVAL:
             putOval(g,true,false,startX, startY, currentX, currentY);
             break;
          case RECT:
             putRect(g,true,false,startX, startY, currentX, currentY);
             break;
          case FILLED_OVAL:
             putOval(g,false,true,startX, startY, currentX, currentY);
             break;
          case FILLED_RECT:
             putRect(g,false,true,startX, startY, currentX, currentY);
             break;
          case STROKED_FILLED_OVAL:
             putOval(g,true,true,startX, startY, currentX, currentY);
             break;
          case STROKED_FILLED_RECT:
             putRect(g,true,true,startX, startY, currentX, currentY);
             break;
          }
       }

       /**
        * Set the graphics context g to use the current stroke color and
        * lineWidth.
        */
       private void applyStrokeProperties(Graphics g) {
          if (lineWidth > 1) {
             Graphics2D g2 = (Graphics2D)g;
             g2.setStroke( new BasicStroke(lineWidth,
                                   BasicStroke.CAP_ROUND, BasicStroke.JOIN_MITER) );
          }
          g.setColor(currentStrokeColor);
       }

       /**
        * Set the graphics context g to use the current fill color, taking
        * into account the setting of transparency.  If transparency is on,
        * the RGB components are obtained from the current fill color, and
        * the alpha component is set to 125.
        */
       private void applyFillColor(Graphics g) {
          Color c = currentFillColor;
          if (transparent.isSelected())
             g.setColor(new Color( c.getRed(), c.getGreen(), c.getBlue(), 125 ));
          else
             g.setColor(c);
       }

       /**
        * Draws a rectangle with corners at the points (x1,y1)
        * and (x2,y2).  Nothing is drawn if x1 == x2 or y1 == y2.  The rectangle
        * can be either stroked (that is, the outline is drawn) or filled or both.
        * @param g the graphics context where the rectangle is drawn
        * @param stroked tells whether to draw an outline of the rectangle.
        * @param filled tells whether to draw a filled or unfilled rectangle.
        */
       private void putRect(Graphics g, boolean stroked, boolean filled,
                                          int x1, int y1, int x2, int y2) {
          assert stroked || filled;  // It doesn't make sense for both to be false,
                                     //    since then nothing would be drawn.
          if (x1 == x2 || y1 == y2)
             return;
          if (x2 < x1) {  // Swap x1,x2 if necessary to make x2 > x1.
             int temp = x1;
             x1 = x2;
             x2 = temp;
          }
          if (y2 < y1) {  // Swap y1,y2 if necessary to make y2 > y1.
             int temp = y1;
             y1 = y2;
             y2 = temp;
          }
          if (filled) {
             applyFillColor(g);
             g.fillRect(x1,y1,x2-x1,y2-y1);
          }
          if (stroked) {
             applyStrokeProperties(g);
             g.drawRect(x1,y1,x2-x1,y2-y1);
          }
       }

       /**
        * Draws an oval in the rectangle with corners at the points (x1,y1)
        * and (x2,y2).  Nothing is drawn if x1 == x2 or y1 == y2.  The oval
        * can be either stroked (that is, the outline is drawn) or filled or both.
        * @param g the graphics context where the oval is drawn
        * @param stroked tells whether to draw an outline of the oval.
        * @param filled tells whether to draw a filled or unfilled oval.
        */
       private void putOval(Graphics g, boolean stroked, boolean filled,
                                          int x1, int y1, int x2, int y2) {
          assert stroked || filled;  // It doesn't make sense for both to be false,
                                     //    since then nothing would be drawn.
          if (x1 == x2 || y1 == y2)
             return;
          if (x2 < x1) {  // Swap x1,x2 if necessary to make x2 > x1.
             int temp = x1;
             x1 = x2;
             x2 = temp;
          }
          if (y2 < y1) {  // Swap y1,y2 if necessary to make y2 > y1.
             int temp = y1;
             y1 = y2;
             y2 = temp;
          }
          if (filled) {
             applyFillColor(g);
             g.fillOval(x1,y1,x2-x1,y2-y1);
          }
          if (stroked) {
             applyStrokeProperties(g);
             g.drawOval(x1,y1,x2-x1,y2-y1);
          }
       }

       /**
        * Calls the repaint() method of this panel for the rectangle with corners
        * at the points (x1,y1) and (x2,y2).  An extra border is added
        * to the area that is repainted; this allows for the size of the "pen"
        * that is used to draw lines and stroked ovals and rectangles.
        */
       private void repaintRect(int x1, int y1, int x2, int y2) {
          if (x2 < x1) {  // Swap x1,x2 if necessary to make x2 >= x1.
             int temp = x1;
             x1 = x2;
             x2 = temp;
          }
          if (y2 < y1) {  // Swap y1,y2 if necessary to make y2 >= y1.
             int temp = y1;
             y1 = y2;
             y2 = temp;
          }
          x1 -= lineWidth + 1;
          x2 += lineWidth + 1;
          y1 -= lineWidth + 1;
          y2 += lineWidth + 1;
          repaint(x1,y1,x2-x1,y2-y1);
       }

       /**
        * Adds a set of JRadioButtonMenuItems to a JMenu.  All the items are in
        * the same button group and have the same ActionListener.
        * @param menu  the menu to which the items will be added
        * @param commandNames  the names of the items; null values in this array
        *    become separators in the menu.  The name can contain the character "/".
        *    In that case the actual item name is the part of the name that
        *    precedes the "/" and the remainder of the name specifies a
        *    KeyStroke that will be used as the keyboard accelerator key
        *    for the item.
        * @param listener  the ActionListener for the items
        */
       private void createRadioGroup(JMenu menu, String[] commandNames,
                                                       ActionListener listener) {
          ButtonGroup group = new ButtonGroup();
          for ( int i = 0; i < commandNames.length; i++) {
             if (commandNames[i] == null)
                menu.addSeparator();
             else {
                String name = commandNames[i];
                String accel = null;
                if (name.indexOf("/") > 0) {
                   int pos = name.indexOf("/");
                   accel = name.substring(pos+1);
                   name = name.substring(0,pos);
                }
                JRadioButtonMenuItem item = new JRadioButtonMenuItem(name);
                menu.add(item);
                group.add(item);
                item.addActionListener(listener);
                if (accel != null)
                   item.setAccelerator(KeyStroke.getKeyStroke(accel));
                if (i == 0)
                   item.setSelected(true);
             }
          }
       }

       /**
        * Creates a menu bar for use with this panel, with "File", "Edit",
        * "StrokeColor", "FillColor", and "Tool" menus.
        */
       public JMenuBar getMenuBar() {
          JMenuBar menubar = new JMenuBar();
          JMenu fileMenu = new JMenu("File");
          JMenu editMenu = new JMenu("Edit");
          JMenu strokeWidthMenu = new JMenu("StrokeWidth");
          JMenu strokeColorMenu = new JMenu("StrokeColor");
          JMenu fillColorMenu = new JMenu("FillColor");
          JMenu toolMenu = new JMenu("Tool");
          menubar.add(fileMenu);
          menubar.add(editMenu);
          menubar.add(toolMenu);
          menubar.add(strokeWidthMenu);
          menubar.add(strokeColorMenu);
          menubar.add(fillColorMenu);
          ActionListener listener = new MenuHandler();
          JMenuItem item;
          item = new JMenuItem("Open Image File...");
          item.setAccelerator(KeyStroke.getKeyStroke("ctrl O"));
          item.addActionListener(listener);
          fileMenu.add(item);
          item = new JMenuItem("Save PNG File...");
          item.setAccelerator(KeyStroke.getKeyStroke("ctrl S"));
          item.addActionListener(listener);
          fileMenu.add(item);
          item = new JMenuItem("Save JPEG File...");
          item.addActionListener(listener);
          fileMenu.add(item);
          fileMenu.addSeparator();
          item = new JMenuItem("Quit");
          item.setAccelerator(KeyStroke.getKeyStroke("ctrl Q"));
          item.addActionListener(listener);
          fileMenu.add(item);
          item = new JMenuItem("Undo");
          item.setAccelerator(KeyStroke.getKeyStroke("ctrl Z"));
          item.addActionListener(listener);
          editMenu.add(item);
          editMenu.addSeparator();
          item = new JMenuItem("Clear to Color...");
          item.setAccelerator(KeyStroke.getKeyStroke("ctrl K"));
          item.addActionListener(listener);
          editMenu.add(item);

          createRadioGroup( strokeWidthMenu,
                new String[] {
                   "Thickness = 1/ctrl 1", "Thickness = 2/ctrl 2", "Thickness = 3/ctrl 3",
                   "Thickness = 4/ctrl 4",
                   "Thickness = 5/ctrl 5", "Thickness = 7", "Thickness = 10", "Thickness = 15",
                   "Thickness = 20", "Thickness = 25"
                }, listener );

          createRadioGroup( strokeColorMenu,
                new String[] {
                   "Draw With Black/ctrl B", "Draw With White/ctrl W", "Draw With Red",
                   "Draw With Green", "Draw With Blue", "Draw With Yellow",
                   "Custom Drawing Color.../ctrl C"
                }, listener);

          createRadioGroup( fillColorMenu,
                new String[] {
                   "Fill With Black/ctrl shift B", "Fill With White/ctrl shift W", "Fill With Red",
                   "Fill With Green", "Fill With Blue", "Fill With Yellow",
                   "Custom Fill Color.../ctrl shift C"
                }, listener);

          fillColorMenu.addSeparator();
          fillColorMenu.add(transparent);
          transparent.setAccelerator(KeyStroke.getKeyStroke("ctrl T"));

          createRadioGroup( toolMenu,
                new String[] {
                   "Curve/ctrl U", null, "Line/ctrl L", "Rectangle/ctrl R", "Oval/ctrl V",
                   "Filled Rectangle/ctrl alt R", "Filled Oval/ctrl alt V",
                   "Stroked Filled Rectangle/ctrl shift R", "Stroked Filled Oval/ctrl shift V",
                   null, "Smudge/ctrl M", "Erase/ctrl E"
                }, listener);

          return menubar;
       }

       /**
        * This nested class defines the ActionListener that responds when the
        * user selects a command from one of the menus.  It is used in the
        * getMenuBar() method.
        */
       private class MenuHandler implements ActionListener {
          public void actionPerformed(ActionEvent evt) {
             String command = evt.getActionCommand();
             if (command.equals("Custom Drawing Color...")) {
                Color newColor = JColorChooser.showDialog(PaintWithOSCFinal.this,
                      "Select Drawing Color", currentStrokeColor);
                if (newColor != null)
                   currentStrokeColor = newColor;
             }
             else if (command.equals("Custom Fill Color...")) {
                Color newColor = JColorChooser.showDialog(PaintWithOSCFinal.this,
                      "Select Fill Color", currentFillColor);
                if (newColor != null)
                   currentFillColor = newColor;
             }
             else if (command.equals("Clear to Color...")) {
                Color newColor = JColorChooser.showDialog(PaintWithOSCFinal.this,
                      "Select Background Color", fillColor);
                if (newColor != null) {
                   fillColor = newColor;
                   saveUndoImage();
                   Graphics osg = OSC.createGraphics();
                   osg.setColor(fillColor);
                   osg.fillRect(0,0,OSC.getWidth(),OSC.getHeight());
                   osg.dispose();
                   PaintWithOSCFinal.this.repaint();
                }
             }
             else if (command.startsWith("Thickness = "))
                lineWidth = Integer.parseInt(command.substring(12));
             else if (command.equals("Draw With Black"))
                currentStrokeColor = Color.BLACK;
             else if (command.equals("Draw With White"))
                currentStrokeColor = Color.WHITE;
             else if (command.equals("Draw With Red"))
                currentStrokeColor = Color.RED;
             else if (command.equals("Draw With Green"))
                currentStrokeColor = Color.GREEN;
             else if (command.equals("Draw With Blue"))
                currentStrokeColor = Color.BLUE;
             else if (command.equals("Draw With Yellow"))
                currentStrokeColor = Color.YELLOW;
             else if (command.equals("Fill With Black"))
                currentFillColor = Color.BLACK;
             else if (command.equals("Fill With White"))
                currentFillColor = Color.WHITE;
             else if (command.equals("Fill With Red"))
                currentFillColor = Color.RED;
             else if (command.equals("Fill With Green"))
                currentFillColor = Color.GREEN;
             else if (command.equals("Fill With Blue"))
                currentFillColor = Color.BLUE;
             else if (command.equals("Fill With Yellow"))
                currentFillColor = Color.YELLOW;
             else if (command.equals("Curve"))
                currentTool = Tool.CURVE;
             else if (command.equals("Line"))
                currentTool = Tool.LINE;
             else if (command.equals("Rectangle"))
                currentTool = Tool.RECT;
             else if (command.equals("Oval"))
                currentTool = Tool.OVAL;
             else if (command.equals("Filled Rectangle"))
                currentTool = Tool.FILLED_RECT;
             else if (command.equals("Filled Oval"))
                currentTool = Tool.FILLED_OVAL;
             else if (command.equals("Stroked Filled Rectangle"))
                currentTool = Tool.STROKED_FILLED_RECT;
             else if (command.equals("Stroked Filled Oval"))
                currentTool = Tool.STROKED_FILLED_OVAL;
             else if (command.equals("Smudge"))
                currentTool = Tool.SMUDGE;
             else if (command.equals("Erase"))
                currentTool = Tool.ERASE;
             else if (command.equals("Open Image File..."))
                doOpenFile();
             else if (command.equals("Save PNG File..."))
                doSaveFile("PNG");
             else if (command.equals("Save JPEG File..."))
                doSaveFile("JPEG");
             else if (command.equals("Quit"))
                System.exit(0);
             else if (command.equals("Undo")) {
                BufferedImage temp = OSC;
                OSC = imageSavedForUndo;
                imageSavedForUndo = temp;
                repaint();
             }
          }
       } // end nested class MenuHandler

       /**
        * This nested class defines the object that listens for mouse and
        * mouse motion events on the panel.  It is used in the constructor.
        */
       private class MouseHandler implements MouseListener, MouseMotionListener {

          int prevX, prevY;  // Previous position of mouse during a drag.

          double[][] smudgeRed, smudgeGreen, smudgeBlue;  // data for smudge tool

          /**
           * When the ERASE or SMUDGE tools are used and the mouse jumps
           * from (x1,y1) to (x2,y2), the tool has to be applied to a
           * line of pixel positions between the two points in order to
           * cover the entire line that the mouse moves along.  The change
           * is made to the off-screen canvas, and repaint() is called to
           * copy the changes to the screen.
           */
          void applyToolAlongLine(int x1, int y1, int x2, int y2) {
             Graphics g = OSC.createGraphics();
             Graphics2D g2 = (Graphics2D)g;
             g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                                   RenderingHints.VALUE_ANTIALIAS_ON);
             g.setColor(fillColor);    // (for ERASE only)
             int w = OSC.getWidth();   // (for SMUDGE only)
             int h = OSC.getHeight();  // (for SMUDGE only)
             int dist = Math.max(Math.abs(x2-x1),Math.abs(y2-y1));
                 // dist is the number of points along the line from
                 // (x1,y1) to (x2,y2) at which the tool will be applied.
             double dx = (double)(x2-x1)/dist;
             double dy = (double)(y2-y1)/dist;
             for (int d = 1; d <= dist; d++) {
                    // Apply the tool at one of the points (x,y) along the
                    // line from (x1,y1) to (x2,y2).
                int x = (int)Math.round(x1 + dx*d);
                int y = (int)Math.round(y1 + dy*d);
                if (currentTool == Tool.ERASE) {
                       // Erase a 10-by-10 block of pixels around (x,y)
                   g.fillRect(x-5,y-5,10,10);
                   repaint(x-5,y-5,10,10);
                }
                else {
                      // For the SMUDGE tool, blend some of the color from
                      // the smudgeRed, smudgeGreen, and smudgeBlue arrays
                      // into the pixels in a 7-by-7 block around (x,y), and
                      // vice versa.  The effect is to smear out the color
                      // of pixels that are visited by the tool.
                   for (int i = 0; i < 7; i++)
                      for (int j = 0; j < 7; j++) {
                         int r = y + j - 3;
                         int c = x + i - 3;
                         if (!(r < 0 || r >= h || c < 0 || c >= w || smudgeRed[i][j] == -1)) {
                            int curCol = OSC.getRGB(c,r);
                            int curRed = (curCol >> 16) & 0xFF;
                            int curGreen = (curCol >> 8) & 0xFF;
                            int curBlue = curCol & 0xFF;
                            int newRed = (int)(curRed*0.7 + smudgeRed[i][j]*0.3);
                            int newGreen = (int)(curGreen*0.7 + smudgeGreen[i][j]*0.3);
                            int newBlue = (int)(curBlue*0.7 + smudgeBlue[i][j]*0.3);
                            int newCol = newRed << 16 | newGreen << 8 | newBlue;
                            OSC.setRGB(c,r,newCol);
                            smudgeRed[i][j] = curRed*0.3 + smudgeRed[i][j]*0.7;
                            smudgeGreen[i][j] = curGreen*0.3 + smudgeGreen[i][j]*0.7;
                            smudgeBlue[i][j] = curBlue*0.3 + smudgeBlue[i][j]*0.7;
                         }
                      }
                   repaint(x-3,y-3,7,7);
                }
             }
             g.dispose();
          }

          /**
           * Start a drag operation.
           */
          public void mousePressed(MouseEvent evt) {
             startX = prevX = currentX = evt.getX();
             startY = prevY = currentY = evt.getY();
             dragging = true;
             saveUndoImage();
             if (currentTool == Tool.ERASE) {
                   // Erase a 10-by-10 block around the starting mouse position.
                Graphics g = OSC.createGraphics();
                Graphics2D g2 = (Graphics2D)g;
                g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                                      RenderingHints.VALUE_ANTIALIAS_ON);
                g.setColor(fillColor);
                g.fillRect(startX-5,startY-5,10,10);
                g.dispose();
                repaint(startX-5,startY-5,10,10);
             }
             else if (currentTool == Tool.SMUDGE) {
                    // Record the colors in a 7-by-7 block of pixels around the
                    // starting mouse position into the arrays smudgeRed,
                    // smudgeGreen, and smudgeBlue.  These arrays hold the
                    // red, green, and blue components of the colors.
                if (smudgeRed == null) {
                      // Create the arrays, if they have not already been created.
                   smudgeRed = new double[7][7];
                   smudgeGreen = new double[7][7];
                   smudgeBlue = new double[7][7];
                }
                int w = OSC.getWidth();
                int h = OSC.getHeight();
                int x = evt.getX();
                int y = evt.getY();
                for (int i = 0; i < 7; i++)
                   for (int j = 0; j < 7; j++) {
                      int r = y + j - 3;
                      int c = x + i - 3;
                      if (r < 0 || r >= h || c < 0 || c >= w) {
                            // A -1 in the smudgeRed array indicates that the
                            // corresponding pixel was outside the canvas.
                         smudgeRed[i][j] = -1;
                      }
                      else {
                         int color = OSC.getRGB(c,r);
                         smudgeRed[i][j] = (color >> 16) & 0xFF;
                         smudgeGreen[i][j] = (color >> 8) & 0xFF;
                         smudgeBlue[i][j] = color & 0xFF;
                      }
                   }
             }
          }

          /**
           * Continue a drag operation when the user drags the mouse.
           * For the CURVE tool, a line is drawn from the previous mouse
           * position to the current mouse position in the off-screen canvas,
           * and the repaint() method is called for a rectangle that contains
           * the line segment that was drawn.  For shape tools, the off-screen
           * canvas is not changed, but the repaint() method is called so
           * that the paintComponent() method can redraw the picture with
           * the user's shape in the new position.  For the SMUDGE and
           * ERASE tools, the tool is applied along a line from the previous
           * mouse position to the current position;
           */
          public void mouseDragged(MouseEvent evt) {
             currentX = evt.getX();
             currentY = evt.getY();
             if (currentTool == Tool.CURVE) {
                Graphics g = OSC.createGraphics();
                Graphics2D g2 = (Graphics2D)g;
                g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                                      RenderingHints.VALUE_ANTIALIAS_ON);
                applyStrokeProperties(g);
                g.drawLine(prevX,prevY,currentX,currentY);
                g.dispose();
                repaintRect(prevX,prevY,currentX,currentY);
             }
             else if (SHAPE_TOOLS.contains(currentTool)) {
                     // Repaint the rectangles occupied by the previous position of
                     // the shape and by its current position.
                repaintRect(startX,startY,prevX,prevY);
                repaintRect(startX,startY,currentX,currentY);
             }
             else {
                   // Tool has to be ERASE or SMUDGE
                applyToolAlongLine(prevX,prevY,currentX,currentY);
             }
             prevX = currentX;
             prevY = currentY;
          }

          /**
           * Finish a mouse drag operation.  Nothing is done unless the current tool
           * is a shape tool.  For shape tools, the user's shape is drawn to the
           * off-screen canvas, making it a permanent part of the picture, and
           * then the repaint() method is called to show the modified picture
           * on the screen.
           */
          public void mouseReleased(MouseEvent evt) {
             dragging = false;
             if (SHAPE_TOOLS.contains(currentTool)) {
                Graphics g = OSC.createGraphics();
                Graphics2D g2 = (Graphics2D)g;
                g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                                      RenderingHints.VALUE_ANTIALIAS_ON);
                putCurrentShape(g);
                g.dispose();
                repaint();
             }
          }

          public void mouseMoved(MouseEvent evt) { }
          public void mouseClicked(MouseEvent evt) { }
          public void mouseEntered(MouseEvent evt) { }
          public void mouseExited(MouseEvent evt) { }

       } // end nested class MenuHandler

       /**
        * Opens an image file selected by the user.  If the image is read
        * successfully, it replaces the image in the off-screen canvas.
        * (The new image is scaled to fit the canvas size exactly.)
        */
       private void doOpenFile() {
          if (fileDialog == null)
             fileDialog = new JFileChooser();
          fileDialog.setDialogTitle("Select File to be Opened");
          fileDialog.setSelectedFile(null);  // No file is initially selected.
          int option = fileDialog.showOpenDialog(this);
          if (option != JFileChooser.APPROVE_OPTION)
             return;  // User canceled or clicked the dialog's close box.
          File selectedFile = fileDialog.getSelectedFile();
          FileInputStream stream;
          try {
             stream = new FileInputStream(selectedFile);
          }
          catch (Exception e) {
             JOptionPane.showMessageDialog(this,
                   "Sorry, but an error occurred while trying to open the file:\n" + e);
             return;
          }
          try {
             BufferedImage image = ImageIO.read(stream);
             if (image == null)
                throw new Exception("File does not contain a recognized image format.");
             saveUndoImage();
             Graphics g = OSC.createGraphics();
             g.drawImage(image,0,0,OSC.getWidth(),OSC.getHeight(),null);
             g.dispose();
             repaint();
          }
          catch (Exception e) {
             JOptionPane.showMessageDialog(this,
                   "Sorry, but an error occurred while trying to read the image:\n" + e);
          }
       }

       /**
        * Attempts to save the current image to a file selected by the user.
        * @param format the format of the image, either "PNG" or "JPEG" in this program
        */
       private void doSaveFile(String format) {
          if (fileDialog == null)
             fileDialog = new JFileChooser();
          fileDialog.setSelectedFile(new File("image." + format.toLowerCase()));
          fileDialog.setDialogTitle("Select File to be Saved");
          int option = fileDialog.showSaveDialog(null);
          if (option != JFileChooser.APPROVE_OPTION)
             return;  // User canceled or clicked the dialog's close box.
          File selectedFile = fileDialog.getSelectedFile();
          if (selectedFile.exists()) {  // Ask the user whether to replace the file.
             int response = JOptionPane.showConfirmDialog( null,
                   "The file \"" + selectedFile.getName()
                   + "\" already exists.\nDo you want to replace it?",
                   "Confirm Save",
                   JOptionPane.YES_NO_OPTION,
                   JOptionPane.WARNING_MESSAGE );
             if (response != JOptionPane.YES_OPTION)
                return;  // User does not want to replace the file.
          }
          try {
             boolean hasFormat = ImageIO.write(OSC,format,selectedFile);
             if ( ! hasFormat )
                throw new Exception(format + " format is not available.");
          }
          catch (Exception e) {
             System.out.println("Sorry, but an error occurred while trying to save the image.");
             e.printStackTrace();
          }
       }

    } // end class PaintWithOSCFinal

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