Help making an eraser for a paint program in java

Making a very basic paint program for a class and one of the requirements is that we must make an eraser. Not sure how to do that, We are using a bufferedimage that is then getting pasted to our jframe. Any ideas on how this could be done/ any code examples? Someone told me to try clearRect but maybe I was just using it wrong but i could not get it to accept it. Any help / code examples would be great, here is my code, its all one class.

     import javax.imageio.ImageIO;
     import javax.swing.*;
     import javax.swing.border.Border;
     import javax.swing.border.LineBorder;

     import java.awt.*;
     import java.awt.event.*;
     import java.awt.image.BufferedImage;
     import java.io.File;
     import java.io.IOException;
     import java.util.*;


     public class PaintProgram extends JPanel implements MouseListener,ActionListener
     {
public static int stroke, eraser = 0;
private int xX1, yY1 , xX2, yY2, choice ;

public static void main(String [] args)
{
    new PaintProgram();
}

PaintProgram()
{


    JFrame frame = new JFrame("Paint Program");
    frame.setSize(1200, 800);
    frame.setBackground(Color.WHITE);
    frame.getContentPane().add(this);


    JMenuBar menuBar = new JMenuBar();
    frame.setJMenuBar(menuBar);
    JMenu help = new JMenu("Help");
    menuBar.add(help);
    JMenuItem about = new JMenuItem("About");
    help.add(about);
    about.addActionListener(this);



    JButton button1 = new JButton("Clear");
    button1.addActionListener(this);
    JButton color = new JButton("Color");
    color.addActionListener(this);
    JButton erase = new JButton("Erase?");
    erase.addActionListener(this);
    JButton button2 = new JButton("Empty Rect");
    button2.addActionListener(this);
    JButton button3 = new JButton("Filled oval");
    button3.addActionListener(this);
    JButton button4 = new JButton("Filled Rect");
    button4.addActionListener(this);
    JButton button5 = new JButton("Empty oval");
    button5.addActionListener(this);
    JButton button6 = new JButton("Line");
    button6.addActionListener(this);
    JRadioButton thin = new JRadioButton("Thin Line");
    thin.addActionListener(this);
    JRadioButton medium = new JRadioButton("Medium Line");
    medium.addActionListener(this);
    JRadioButton thick = new JRadioButton("Thick Line");
    thick.addActionListener(this);


    ButtonGroup lineOption = new ButtonGroup( );
    lineOption.add(thin);
    lineOption.add(medium);
    lineOption.add(thick);

   this.add(button1); 
   this.add(color);
   this.add(erase);
   this.add(button2);
   this.add(button3);
   this.add(button4);
   this.add(button5);
   this.add(button6);
   this.add(thin);
   this.add(medium);
   this.add(thick);
   addMouseListener(this);
   frame.setVisible(true);
   frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);



}

public void paintComponent(Graphics g)
{ 
     super.paintComponent(g);  
     Graphics2D g2 = (Graphics2D)g;
     if(grid == null){
        int w = this.getWidth();
        int h = this.getHeight();
        grid = (BufferedImage)(this.createImage(w,h));
        gc = grid.createGraphics();
        gc.setColor(Color.BLUE);
     }

     g2.drawImage(grid, null, 0, 0);
     check();
}
BufferedImage grid;
Graphics2D gc;


public void draw()
{
    Graphics2D g = (Graphics2D)getGraphics();
     int w = xX2 - xX1;
        if (w<0)
        w = w *(-1);

   int h = yY2-yY1;
        if (h<0)
  开发者_如何转开发      h=  h*(-1);

     switch(choice)
    {
        case 1:
            check();
            gc.drawRect(xX1, yY1, w, h);
            repaint();
            break;

        case 2:
            check();
            gc.drawOval(xX1, yY1, w, h);
            repaint();
            break;

        case 3:
            check();
            gc.drawRect(xX1, yY1, w, h);
            gc.fillRect(xX1, yY1, w, h);
            repaint();
            break;

        case 4:
            check();
            gc.drawOval(xX1, yY1, w, h);
            gc.fillOval(xX1, yY1, w, h);
            repaint();
            break;  

        case 5:

            if (stroke == 0)
            gc.setStroke(new BasicStroke (1));
            if (stroke == 1)
            gc.setStroke(new BasicStroke (3));
            if (stroke == 2)
            gc.setStroke(new BasicStroke (6));
            gc.drawLine(xX1, yY1, xX2, yY2);
            repaint();
            break;

        case 6:
            repaint();
            Color temp = gc.getColor();
            gc.setColor(Color.WHITE);
            gc.fillRect(0, 0, getWidth(), getHeight());
            gc.setColor(temp);
            repaint();
            break;   

        case 7:

            if (eraser == 1)
            {
                gc.clearRect(xX1, yY1, w, h);
            }
            else
            {

            }
            break;
    }
}

public void check()
{
    if (xX1 > xX2)
    {
        int z = 0;
        z = xX1;
        xX1 = xX2;
        xX2 =z;
    }
    if (yY1 > yY2)
    {
        int z = 0;
        z = yY1;
        yY1 = yY2;
        yY2 = z;
    }
}




public void actionPerformed(ActionEvent e)
{

if (e.getActionCommand().equals("Color"))
{
     Color bgColor
     = JColorChooser.showDialog(this,"Choose Background Color", getBackground());
   if (bgColor != null)
     gc.setColor(bgColor);
}


if (e.getActionCommand().equals("About"))
{
    System.out.println("About Has Been Pressed");
    JFrame about = new JFrame("About");
    about.setSize(300, 300);
    JButton picture = new JButton(new ImageIcon("C:/Users/TehRobot/Desktop/Logo.png"));
    about.add(picture);
    about.setVisible(true);
}

if (e.getActionCommand().equals("Empty Rect")) 
{         
  System.out.println("Empty Rectangle Has Been Selected~");
   choice = 1;

  }

if (e.getActionCommand().equals("Empty oval")) 
{         
 System.out.println("Empty Oval Has Been Selected!");
   choice = 2;
  }


if (e.getActionCommand().equals("Filled Rect"))
{         
  System.out.println("Filled Rectangle Has Been Selected");
   choice = 3;
  }


if (e.getActionCommand().equals("Filled oval")) 
{         
 System.out.println("Filled Oval Has Been Selected");
   choice = 4;
  }


if (e.getActionCommand().equals("Line"))
{
    System.out.println("Draw Line Has Been Selected");
    choice = 5;
}

if (e.getActionCommand().equals("Thin Line"))
{
    stroke = 0;
}

if (e.getActionCommand().equals("Medium Line"))
{
    stroke = 1;
}

if (e.getActionCommand().equals("Thick Line"))
{
    stroke = 2;
}

if(e.getActionCommand().equals("Erase?"))
{
    eraser = 1;
    choice = 7;
}

if (e.getActionCommand().equals("Clear"))
{         
    System.out.println("Clear All The Things!!!");
    choice = 6;
    draw();
}


 }

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

     xX1 = evt.getX();
     yY1= evt.getY();



   }
 public void mouseReleased(MouseEvent evt)
 {
     xX2 =evt.getX();
     yY2=evt.getY();
     draw();
     eraser = 0;
   }

}

---

I have added comments where I added/changed the code.

import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import java.awt.image.BufferedImage;

import javax.swing.ButtonGroup;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JColorChooser;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JPanel;
import javax.swing.JRadioButton;

public class PaintProgram extends JPanel implements MouseListener, ActionListener,
/**
 * CHANGE BY S AQEEL : implement mouse motion listener
 */
MouseMotionListener
{
    /**
     * 
     */
    private static final long serialVersionUID = 1L;
    public static int stroke, eraser = 0;
    private int xX1, yY1, xX2, yY2, choice;

    /**
     * CHANGE BY S AQEEL : Define a constant for background color, because we are using it at a lot of places
     */
    private static final Color BACKGROUND_COLOR = Color.WHITE;

    /**
     * CHANGE BY S AQEEL : Also define variables for eraser width and height. In a more usable implementation you can allow user to change eraser size
     */
    private int eraserWidth = 40;
    private int eraserHeight = 40;

    public static void main(String[] args)
    {
        new PaintProgram();
    }

    PaintProgram()
    {

        JFrame frame = new JFrame("Paint Program");
        frame.setSize(1200, 800);

        /**
         * CHANGE BY S AQEEL : Use constant instead of hardcoding
         */
        frame.setBackground(BACKGROUND_COLOR);
        frame.getContentPane().add(this);

        JMenuBar menuBar = new JMenuBar();
        frame.setJMenuBar(menuBar);
        JMenu help = new JMenu("Help");
        menuBar.add(help);
        JMenuItem about = new JMenuItem("About");
        help.add(about);
        about.addActionListener(this);

        JButton button1 = new JButton("Clear");
        button1.addActionListener(this);
        JButton color = new JButton("Color");
        color.addActionListener(this);
        JButton erase = new JButton("Erase?");
        erase.addActionListener(this);
        JButton button2 = new JButton("Empty Rect");
        button2.addActionListener(this);
        JButton button3 = new JButton("Filled oval");
        button3.addActionListener(this);
        JButton button4 = new JButton("Filled Rect");
        button4.addActionListener(this);
        JButton button5 = new JButton("Empty oval");
        button5.addActionListener(this);
        JButton button6 = new JButton("Line");
        button6.addActionListener(this);
        JRadioButton thin = new JRadioButton("Thin Line");
        thin.addActionListener(this);
        JRadioButton medium = new JRadioButton("Medium Line");
        medium.addActionListener(this);
        JRadioButton thick = new JRadioButton("Thick Line");
        thick.addActionListener(this);

        ButtonGroup lineOption = new ButtonGroup();
        lineOption.add(thin);
        lineOption.add(medium);
        lineOption.add(thick);

        this.add(button1);
        this.add(color);
        this.add(erase);
        this.add(button2);
        this.add(button3);
        this.add(button4);
        this.add(button5);
        this.add(button6);
        this.add(thin);
        this.add(medium);
        this.add(thick);
        addMouseListener(this);
        frame.setVisible(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    }

    public void paintComponent(Graphics g)
    {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D) g;
        if (grid == null)
        {
            int w = this.getWidth();
            int h = this.getHeight();
            grid = (BufferedImage) (this.createImage(w, h));
            gc = grid.createGraphics();
            gc.setColor(Color.BLUE);
        }

        g2.drawImage(grid, null, 0, 0);
        check();
    }

    BufferedImage grid;
    Graphics2D gc;

    public void draw()
    {
        Graphics2D g = (Graphics2D) getGraphics();
        int w = xX2 - xX1;
        if (w < 0)
            w = w * (-1);

        int h = yY2 - yY1;
        if (h < 0)
            h = h * (-1);

        switch (choice)
        {
        case 1:
            check();
            gc.drawRect(xX1, yY1, w, h);
            repaint();
            break;

        case 2:
            check();
            gc.drawOval(xX1, yY1, w, h);
            repaint();
            break;

        case 3:
            check();
            gc.drawRect(xX1, yY1, w, h);
            gc.fillRect(xX1, yY1, w, h);
            repaint();
            break;

        case 4:
            check();
            gc.drawOval(xX1, yY1, w, h);
            gc.fillOval(xX1, yY1, w, h);
            repaint();
            break;

        case 5:

            if (stroke == 0)
                gc.setStroke(new BasicStroke(1));
            if (stroke == 1)
                gc.setStroke(new BasicStroke(3));
            if (stroke == 2)
                gc.setStroke(new BasicStroke(6));
            gc.drawLine(xX1, yY1, xX2, yY2);
            repaint();
            break;

        case 6:
            repaint();
            Color temp = gc.getColor();

            /**
             * CHANGE BY S AQEEL : Use constant instead of hardcoding
             */
            gc.setColor(BACKGROUND_COLOR);
            gc.fillRect(0, 0, getWidth(), getHeight());
            gc.setColor(temp);
            repaint();
            break;

        case 7:

            if (eraser == 1)
            {
                gc.clearRect(xX1, yY1, w, h);
            }
            else
            {

            }
            break;
        }
    }

    public void check()
    {
        if (xX1 > xX2)
        {
            int z = 0;
            z = xX1;
            xX1 = xX2;
            xX2 = z;
        }
        if (yY1 > yY2)
        {
            int z = 0;
            z = yY1;
            yY1 = yY2;
            yY2 = z;
        }
    }

    public void actionPerformed(ActionEvent e)
    {
        /**
         * CHANGE BY S AQEEL : Remove mousemotionlistener(which is added when eraser is selected) So that if another control is pressed, the user does
         * not accidentally erases
         */
        super.removeMouseMotionListener(this);

        if (e.getActionCommand().equals("Color"))
        {
            Color bgColor = JColorChooser.showDialog(this, "Choose Background Color", getBackground());
            if (bgColor != null)
                gc.setColor(bgColor);
        }

        if (e.getActionCommand().equals("About"))
        {
            System.out.println("About Has Been Pressed");
            JFrame about = new JFrame("About");
            about.setSize(300, 300);
            JButton picture = new JButton(new ImageIcon("C:/Users/TehRobot/Desktop/Logo.png"));
            about.add(picture);
            about.setVisible(true);
        }

        if (e.getActionCommand().equals("Empty Rect"))
        {
            System.out.println("Empty Rectangle Has Been Selected~");
            choice = 1;

        }

        if (e.getActionCommand().equals("Empty oval"))
        {
            System.out.println("Empty Oval Has Been Selected!");
            choice = 2;
        }

        if (e.getActionCommand().equals("Filled Rect"))
        {
            System.out.println("Filled Rectangle Has Been Selected");
            choice = 3;
        }

        if (e.getActionCommand().equals("Filled oval"))
        {
            System.out.println("Filled Oval Has Been Selected");
            choice = 4;
        }

        if (e.getActionCommand().equals("Line"))
        {
            System.out.println("Draw Line Has Been Selected");
            choice = 5;
        }

        if (e.getActionCommand().equals("Thin Line"))
        {
            stroke = 0;
        }

        if (e.getActionCommand().equals("Medium Line"))
        {
            stroke = 1;
        }

        if (e.getActionCommand().equals("Thick Line"))
        {
            stroke = 2;
        }

        if (e.getActionCommand().equals("Erase?"))
        {
            eraser = 1;
            choice = 7;

            /**
             * CHANGE BY S AQEEL : Add mousemotionlistener here.
             */
            super.addMouseMotionListener(this);
        }

        if (e.getActionCommand().equals("Clear"))
        {
            System.out.println("Clear All The Things!!!");
            choice = 6;
            draw();
        }

    }

    public void mouseExited(MouseEvent evt)
    {
    }

    public void mouseEntered(MouseEvent evt)
    {
    }

    public void mouseClicked(MouseEvent evt)
    {
    }

    public void mousePressed(MouseEvent evt)
    {

        xX1 = evt.getX();
        yY1 = evt.getY();

    }

    public void mouseReleased(MouseEvent evt)
    {
        xX2 = evt.getX();
        yY2 = evt.getY();
        draw();
        eraser = 0;
    }

    /**
     * CHANGE BY S AQEEL : MouseMotionListener functions implemented. Note this listener is only registered when eraser is selected
     */
    public void mouseDragged(MouseEvent me)
    {
        Color c = gc.getColor();
        gc.setColor(BACKGROUND_COLOR);
        gc.drawRect(me.getX(), me.getY(), eraserWidth, eraserHeight);
        gc.fillRect(me.getX(), me.getY(), eraserWidth, eraserHeight);
        gc.setColor(c);
        repaint();
    }

    public void mouseMoved(MouseEvent arg0)
    {
    }
}

Now that your problem is solved, you should try to add little but usable quality features, like: Using different cursors for drawing/erasing different shapes. Allow user to change eraser size. Also in the current implementation, the user have to drag the eraser to erase, you should add a functionality so that user can erase points by just clicking (besides dragging).

---

An eraser is just like the pen, except that it sets the color to the background color. When you erase you replace the current color under the pen with the "background" color, which makes it look like the background, effectively removing the perceived color that was previously drawn on the screen.

If your application handles transparencies, then perhaps your eraser will set the color to transparent; but it's the same idea, as "transparency" is just one of the color components, like red, green, and blue.

In the event that you want a button to erase the entire drawing, then simply draw a rectangle as large as the screen in the background color.