1. Write a program that draws the patterns shown in Figure 3G.33 onto a DrawingP
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Question
1. Write a program that draws the patterns shown in Figure 3G.33 onto a DrawingPanel Figure 3G.33 The DrawingPanel's size is 400 × 400 pixels and its background color is cyan. It contains four figures of concentric yellow circles with black outlines, all surrounded by a green rectangle with a black outline. The four figures on your DrawingPanel should have the properties shown in Table 3G.7. Table 3G.7 Circle Figure Properties Number of circles Number of rows/cols Description top left bottom left top right bottom right1 (x, y) position (0, 0) (10, 120) (150, 20) (130, 275) Size of subfigures 100× 100 24 x 24 40 x 40 36×36 5 x 5 Break down your program into methods for drawing one subfigure as well as larger grids of subfigures, such as the 5 x 5 grid at (10, 120)Explanation / Answer
pattern 1
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
public class SimplePaint2 extends Applet {
public void init() {
setBackground(Color.gray); // Background color of applet.
setLayout(new BorderLayout(3,3)); // Layout manager for applet.
SimplePaintCanvas canvas = new SimplePaintCanvas(); // The drawing area.
add(canvas,BorderLayout.CENTER);
Panel buttonBar = new Panel(); // A panel to hold the controls.
add(buttonBar, BorderLayout.SOUTH);
Choice choice = new Choice(); // The pop-up ment of colors.
choice.addItem("Black");
choice.addItem("Red");
choice.addItem("Green");
choice.addItem("Blue");
choice.addItem("Cyan");
choice.addItem("Magenta");
choice.addItem("Yellow");
choice.addItem("White");
choice.setBackground(Color.white);
buttonBar.add(choice);
Button fill = new Button("Set Background"); // The first button.
fill.addActionListener(canvas);
fill.setBackground(Color.lightGray);
buttonBar.add(fill);
Button clear = new Button("Clear"); // The second button.
clear.addActionListener(canvas);
clear.setBackground(Color.lightGray);
buttonBar.add(clear);
canvas.colorChoice = choice; // Canvas needs access to the pop-up menu,
// so it can check it to find out what
// color to use.
} // end init()
public Insets getInsets() {
// Specify how wide a border to leave around the edges of the applet.
return new Insets(3,3,3,3);
}
} // end class SimplePaint2
class SimplePaintCanvas extends Canvas
implements MouseListener, MouseMotionListener, ActionListener {
// A SimplePaintCanvas lets the user use the mouse to draw colored
// curves. The current color is specified by a pop-up menu which
// must be created by the applet and assigned to the instance variable
// colorChoice. The applet listens for action events from buttons
// named "Clear" and "Set Background". The "Clear" button fills
// the canvas with the current background color. The "Set Background"
// sets the background color to the current drawing color and
// then clears.
private final static int
BLACK = 0,
RED = 1, // Some constants to make
GREEN = 2, // the code more readable.
BLUE = 3, // These numbers code for
CYAN = 4, // the differnet drawing colors.
MAGENTA = 5,
YELLOW = 6;
Choice colorChoice; // A Choice object, containing the possible drawing
// colors, which must be created by the applet.
/* The following variables are used when the user is sketching a
curve while dragging a mouse. */
private int prevX, prevY; // The previous location of the mouse.
private boolean dragging; // This is set to true while the user is drawing.
private Graphics graphicsForDrawing; // A graphics context for the applet
// that is used to draw the user's curve.
SimplePaintCanvas() {
// Constructor. When the canvas is first created, it is set to
// listen for mouse events and mouse motion events from
// itself. The initial background color is white.
addMouseListener(this);
addMouseMotionListener(this);
setBackground(Color.white);
}
public void actionPerformed(ActionEvent evt) {
// Respond when the user clicks on a button.
String command = evt.getActionCommand();
if (command.equals("Clear")) {
// Clear to current background color.
repaint();
}
else if (command.equals("Set Background")) {
// Set background color, then clear.
setBackground(getCurrentColor());
repaint();
}
}
private Color getCurrentColor() {
// Check the colorChoice menu to find the currently
// selected color, and return the appropriate color
// object.
int currentColor = colorChoice.getSelectedIndex();
switch (currentColor) {
case BLACK:
return Color.black;
case RED:
return Color.red;
case GREEN:
return Color.green;
case BLUE:
return Color.blue;
case CYAN:
return Color.cyan;
case MAGENTA:
return Color.magenta;
case YELLOW:
return Color.yellow;
default:
return Color.white;
}
}
public void mousePressed(MouseEvent evt) {
// This is called when the user presses the mouse on the
// canvas. This begins a draw operation in which the user
// sketches a curve.
if (dragging == true) // Ignore mouse presses that occur
return; // when user is already drawing a curve.
// (This can happen if the user presses
// two mouse buttons at the same time.)
prevX = evt.getX(); // Start drawing.
prevY = evt.getY();
dragging = true;
graphicsForDrawing = getGraphics();
graphicsForDrawing.setColor(getCurrentColor());
} // end mousePressed()
public void mouseReleased(MouseEvent evt) {
// Called whenever the user releases the mouse button.
// If the user was drawing a curve, the curve is done,
// so we should set drawing to false and get rid of
// the graphics context that we created to use during
// the drawing.
if (dragging == false)
return; // Nothing to do because the user isn't drawing.
dragging = false;
graphicsForDrawing.dispose();
graphicsForDrawing = null;
}
public void mouseDragged(MouseEvent evt) {
// Called whenever the user moves the mouse
// while a mouse button is held down. If the
// user is drawing, draw a line segment from the
// previous mouse location to the current mouse
// location, and set up prevX and prevY for the
// next call.
if (dragging == false)
return; // Nothing to do because the user isn't drawing.
int x = evt.getX(); // x-coordinate of mouse.
int y = evt.getY(); // y=coordinate of mouse.
graphicsForDrawing.drawLine(prevX, prevY, x, y); // Draw the line.
prevX = x; // Get ready for the next line segment in the curve.
prevY = y;
} // end mouseDragged.
public void mouseEntered(MouseEvent evt) { } // Some empty routines.
public void mouseExited(MouseEvent evt) { } // (Required by the MouseListener
public void mouseClicked(MouseEvent evt) { } // and MouseMotionListener
public void mouseMoved(MouseEvent evt) { } // interfaces).
} // end class SimplePaintCanvas
pattern 2:
/*
A simple program where the user can sketch curves and shapes in a
variety of colors on a variety of background colors. The user selects
a drawing color form a pop-up menu at the top of the
applet. If the user clicks "Set Background", the background
color is set to the current drawing color and the drawing
area is filled with that color. If the user clicks "Clear",
the drawing area is just filled with the current background color.
The user selects the shape to draw from another pop-up menu at the
top of the applet. The user can draw free-hand curves, straight
lines, and one of six different types of shapes.
The user's drawing is saved in an off-screen image, which is
used to refresh the screen when repainting. The picture is
lost if the applet changes size, however.
This file defines two classes, SimplePaint3,class, and
class, SimplePaint3$Display.class.
*/
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class SimplePaint3 extends JApplet {
JComboBox colorChoice, figureChoice; // Pop-up menus, defined as instance
// variables so that the Display
// class can see them.
public void init() {
setBackground(Color.gray);
getContentPane().setBackground(Color.gray);
Display canvas = new Display(); // The drawing area.
getContentPane().add(canvas,BorderLayout.CENTER);
JPanel buttonBar = new JPanel(); // A panel to hold the buttons.
buttonBar.setBackground(Color.gray);
getContentPane().add(buttonBar, BorderLayout.SOUTH);
JPanel choiceBar = new JPanel(); // A panel to hole the pop-up menus
choiceBar.setBackground(Color.gray);
getContentPane().add(choiceBar, BorderLayout.NORTH);
JButton fill = new JButton("Set Background"); // The first button.
fill.addActionListener(canvas);
buttonBar.add(fill);
JButton clear = new JButton("Clear"); // The second button.
clear.addActionListener(canvas);
buttonBar.add(clear);
colorChoice = new JComboBox(); // The pop-up menu of colors.
colorChoice.addItem("Black");
colorChoice.addItem("Red");
colorChoice.addItem("Green");
colorChoice.addItem("Blue");
colorChoice.addItem("Cyan");
colorChoice.addItem("Magenta");
colorChoice.addItem("Yellow");
colorChoice.addItem("White");
colorChoice.setBackground(Color.white);
choiceBar.add(colorChoice);
figureChoice = new JComboBox(); // The pop-up menu of shapes.
figureChoice.addItem("Curve");
figureChoice.addItem("Straight Line");
figureChoice.addItem("Rectangle");
figureChoice.addItem("Oval");
figureChoice.addItem("RoundRect");
figureChoice.addItem("Filled Rectangle");
figureChoice.addItem("Filled Oval");
figureChoice.addItem("Filled RoundRect");
figureChoice.setBackground(Color.white);
choiceBar.add(figureChoice);
} // end init()
public Insets getInsets() {
// Specify how wide a border to leave around the edges of the applet.
return new Insets(3,3,3,3);
}
private class Display extends JPanel
implements MouseListener, MouseMotionListener, ActionListener {
private final static int
BLACK = 0,
RED = 1, // Some constants to make
GREEN = 2, // the code more readable.
BLUE = 3, // These numbers code for
CYAN = 4, // the different drawing colors.
MAGENTA = 5,
YELLOW = 6,
WHITE = 7;
private final static int
CURVE = 0,
LINE = 1,
RECT = 2, // Some constants that code
OVAL = 3, // for the different types of
ROUNDRECT = 4, // figure the program can draw.
FILLED_RECT = 5,
FILLED_OVAL = 6,
FILLED_ROUNDRECT = 7;
/* Some variables used for backing up the contents of the panel. */
Image OSI; // The off-screen image (created in checkOSI()).
int widthOfOSI, heightOfOSI;
/* The following variables are used when the user is sketching a
curve while dragging a mouse. */
private int mouseX, mouseY; // The location of the mouse.
private int prevX, prevY; // The previous location of the mouse.
private int startX, startY; // The starting position of the mouse.
// (Not used for drawing curves.)
private boolean dragging; // This is set to true when the user is drawing.
private int figure; // What type of figure is being drawn. This is
// specified by the figureChoice menu.
private Graphics dragGraphics; // A graphics context for the off-screen image,
// to be used while a drag is in progress.
private Color dragColor; // The color that is used for the figure that is
// being drawn.
Display() {
addMouseListener(this);
addMouseMotionListener(this);
setBackground(Color.white);
}
private void drawFigure(Graphics g, int shape, int x1, int y1, int x2, int y2) {
// This method is called to do ALL drawing in this applet!
// Draws a shape in the graphics context g.
// The shape paramter tells what kind of shape to draw. This
// can be LINE, RECT, OVAL, ROUNTRECT, FILLED_RECT,
// FILLED_OVAL, or FILLED_ROUNDRECT. (Note that a CURVE is
// drawn by drawing multiple LINES, so the shape parameter is
// never equal to CURVE.) For a LINE, a line is drawn from
// the point (x1,y1) to (x2,y2). For other shapes, the
// points (x1,y1) and (x2,y2) give two corners of the shape
// (or of a rectangle that contains the shape).
if (shape == LINE) {
// For a line, just draw the line between the two points.
g.drawLine(x1,y1,x2,y2);
return;
}
int x, y; // Top left corner of rectangle that contains the figure.
int w, h; // Width and height of rectangle that contains the figure.
if (x1 >= x2) { // x2 is left edge
x = x2;
w = x1 - x2;
}
else { // x1 is left edge
x = x1;
w = x2 - x1;
}
if (y1 >= y2) { // y2 is top edge
y = y2;
h = y1 - y2;
}
else { // y1 is top edge.
y = y1;
h = y2 - y1;
}
switch (shape) { // Draw the appropriate figure.
case RECT:
g.drawRect(x, y, w, h);
break;
case OVAL:
g.drawOval(x, y, w, h);
break;
case ROUNDRECT:
g.drawRoundRect(x, y, w, h, 20, 20);
break;
case FILLED_RECT:
g.fillRect(x, y, w, h);
break;
case FILLED_OVAL:
g.fillOval(x, y, w, h);
break;
case FILLED_ROUNDRECT:
g.fillRoundRect(x, y, w, h, 20, 20);
break;
}
}
private void repaintRect(int x1, int y1, int x2, int y2) {
// Call repaint on a rectangle that contains the points (x1,y1)
// and (x2,y2). (Add a 1-pixel border along right and bottom
// edges to allow for the pen overhang when drawing a line.)
int x, y; // top left corner of rectangle that contains the figure
int w, h; // width and height of rectangle that contains the figure
if (x2 >= x1) { // x1 is left edge
x = x1;
w = x2 - x1;
}
else { // x2 is left edge
x = x2;
w = x1 - x2;
}
if (y2 >= y1) { // y1 is top edge
y = y1;
h = y2 - y1;
}
else { // y2 is top edge.
y = y2;
h = y1 - y2;
}
repaint(x,y,w+1,h+1);
}
private void checkOSI() {
// This method is responsible for creating the off-screen image.
// It should be called before using the OSI. It will make a new OSI if
// the size of the panel changes.
if (OSI == null || widthOfOSI != getSize().width || heightOfOSI != getSize().height) {
// Create the OSI, or make a new one if panel size has changed.
OSI = null; // (If OSI already exists, this frees up the memory.)
OSI = createImage(getSize().width, getSize().height);
widthOfOSI = getSize().width;
heightOfOSI = getSize().height;
Graphics OSG = OSI.getGraphics(); // Graphics context for drawing to OSI.
OSG.setColor(getBackground());
OSG.fillRect(0, 0, widthOfOSI, heightOfOSI);
OSG.dispose();
}
}
public void paintComponent(Graphics g) {
// Copy the off-screen image to the screen,
// after checking to make sure it exists. Then,
// if a shape other than CURVE is being drawn,
// draw it on top of the image from the OSI.
checkOSI();
g.drawImage(OSI, 0, 0, this);
if (dragging && figure != CURVE) {
g.setColor(dragColor);
drawFigure(g,figure,startX,startY,mouseX,mouseY);
}
}
public void actionPerformed(ActionEvent evt) {
// Respond when the user clicks on a button. The
// command must be either "Clear" or "Set Background".
String command = evt.getActionCommand();
checkOSI();
if (command.equals("Set Background")) {
// Set background color before clearing.
// Change the selected color so it is different
// from the background color.
setBackground(getCurrentColor());
if (colorChoice.getSelectedIndex() == BLACK)
colorChoice.setSelectedIndex(WHITE);
else
colorChoice.setSelectedIndex(BLACK);
}
Graphics g = OSI.getGraphics();
g.setColor(getBackground());
g.fillRect(0,0,getSize().width,getSize().height);
g.dispose();
repaint();
}
private Color getCurrentColor() {
// Check the colorChoice menu to find the currently
// selected color, and return the appropriate color
// object.
int currentColor = colorChoice.getSelectedIndex();
switch (currentColor) {
case BLACK:
return Color.black;
case RED:
return Color.red;
case GREEN:
return Color.green;
case BLUE:
return Color.blue;
case CYAN:
return Color.cyan;
case MAGENTA:
return Color.magenta;
case YELLOW:
return Color.yellow;
default:
return Color.white;
}
}
public void mousePressed(MouseEvent evt) {
if (dragging == true) // Ignore mouse presses that occur
return; // when user is already drawing a curve.
// (This can happen if the user presses
// two mouse buttons at the same time.)
prevX = startX = evt.getX(); // Save mouse coordinates.
prevY = startY = evt.getY();
figure = figureChoice.getSelectedIndex();
dragColor = getCurrentColor();
dragGraphics = OSI.getGraphics();
dragGraphics.setColor(dragColor);
dragging = true; // Start drawing.
} // end mousePressed()
public void mouseReleased(MouseEvent evt) {
// Called whenever the user releases the mouse button.
// If the user was drawing a shape, we make the shape
// permanent by drawing it to the off-screen image.
if (dragging == false)
return; // Nothing to do because the user isn't drawing.
dragging = false;
mouseX = evt.getX();
mouseY = evt.getY();
if (figure == CURVE) {
// A CURVE is drawn as a series of LINEs
drawFigure(dragGraphics,LINE,prevX,prevY,mouseX,mouseY);
repaintRect(prevX,prevY,mouseX,mouseY);
}
else if (figure == LINE) {
repaintRect(startX,startY,prevX,prevY);
if (mouseX != startX || mouseY != startY) {
// Draw the line only if it has non-zero length.
drawFigure(dragGraphics,figure,startX,startY,mouseX,mouseY);
repaintRect(startX,startY,mouseX,mouseY);
}
}
else {
repaintRect(startX,startY,prevX,prevY);
if (mouseX != startX && mouseY != startY) {
// Draw the shape only if both its height
// and width are both non-zero.
drawFigure(dragGraphics,figure,startX,startY,mouseX,mouseY);
repaintRect(startX,startY,mouseX,mouseY);
}
}
dragGraphics.dispose();
dragGraphics = null;
}
public void mouseDragged(MouseEvent evt) {
if (dragging == false)
return; // Nothing to do because the user isn't drawing.
mouseX = evt.getX(); // x-coordinate of mouse.
mouseY = evt.getY(); // y=coordinate of mouse.
if (figure == CURVE) {
// A CURVE is drawn as a series of LINEs.
drawFigure(dragGraphics,LINE,prevX,prevY,mouseX,mouseY);
repaintRect(prevX,prevY,mouseX,mouseY);
}
else {
// Repaint two rectangles: The one that contains the previous
// version of the figure, and the one that will contain the
// new version. The first repaint is necessary to restore
// the picture from the off-screen image in that rectangle.
repaintRect(startX,startY,prevX,prevY);
repaintRect(startX,startY,mouseX,mouseY);
}
prevX = mouseX; // Save coords for the next call to mouseDragged or mouseReleased.
prevY = mouseY;
} // end mouseDragged.
public void mouseEntered(MouseEvent evt) { } // Some empty routines.
public void mouseExited(MouseEvent evt) { } // (Required by the MouseListener
public void mouseClicked(MouseEvent evt) { } // and MouseMotionListener
public void mouseMoved(MouseEvent evt) { } // interfaces).
} // end nested class Display
}
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