An introduction to the Java 2D API
Complete Source Code
---Test2D.java---
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
public class Test2D extends Canvas {
int testNumber = 1;
public Test2D(int num) {
testNumber = num;
setBackground(Color.lightGray);
}
GeneralPath makeLine(int x1, int y1, int x2, int y2) {
GeneralPath p = new GeneralPath();
p.moveTo(x1, y1); p.lineTo(x2, y2);
return p;
}
// makes a cross out of two lines centered at x,y
GeneralPath makeCross(int x, int y, int width) {
GeneralPath p = new GeneralPath();
p.moveTo(x + (width/2), y - (width/2));
p.lineTo(x - (width/2), y + (width/2));
p.moveTo(x - (width/2), y - (width/2));
p.lineTo(x + (width/2), y + (width/2));
return p;
}
// makes a box out of two rectangular pieces one inside the other
GeneralPath makeBox(int x, int y, int width, int height) {
GeneralPath p = new GeneralPath();
p.moveTo(x + (width/2), y - (height/2));
p.lineTo(x + (width/2), y + (height/2));
p.lineTo(x - (width/2), y + (height/2));
p.lineTo(x - (width/2), y - (height/2));
p.closePath();
p.moveTo(x + (width/4), y - (height/4));
p.lineTo(x + (width/4), y + (height/4));
p.lineTo(x - (width/4), y + (height/4));
p.lineTo(x - (width/4), y - (height/4));
p.closePath();
return p;
}
public void test1(Graphics g) {
Dimension sz = getSize();
g.setColor(Color.red);
g.drawRect(10, 10, sz.width-20, sz.height-20);
// Illustrate 2d primitives
Graphics2D g2;
g2 = (Graphics2D) g;
g2.setRenderingHints(Graphics2D.ANTIALIASING, Graphics2D.ANTIALIAS_ON);
GeneralPath p = makeBox(sz.width/4, sz.height/4,
100, 100);
p.setWindingRule(GeneralPath.NON_ZERO);
g2.setColor(Color.blue);
g2.fill(p);
p = makeBox((3 * sz.width)/4, sz.height/4,
100, 100);
p.setWindingRule(GeneralPath.EVEN_ODD);
g2.setColor(Color.blue);
g2.fill(p);
}
public void test2(Graphics g) {
Dimension sz = getSize();
g.setColor(Color.red);
g.drawRect(10, 10, sz.width-20, sz.height-20);
// Illustrate 2d primitives
Graphics2D g2;
g2 = (Graphics2D) g;
g2.setRenderingHints(Graphics2D.ANTIALIASING, Graphics2D.ANTIALIAS_ON);
GeneralPath p = makeBox(sz.width/4, sz.height/4,
100, 100);
p.setWindingRule(GeneralPath.NON_ZERO);
g2.setColor(Color.blue);
g2.setStroke(new BasicStroke(5.0f, BasicStroke.CAP_SQUARE,
BasicStroke.JOIN_MITER, 10.0f,
null, 0.0f));
g2.draw(p);
p = makeBox((3 * sz.width)/4, sz.height/4,
100, 100);
p.setWindingRule(GeneralPath.EVEN_ODD);
g2.setColor(Color.blue);
g2.setStroke(new BasicStroke(15.0f, BasicStroke.CAP_SQUARE,
BasicStroke.JOIN_MITER, 10.0f,
null, 0.0f));
g2.draw(p);
}
public void test3(Graphics g) {
Dimension sz = getSize();
g.setColor(Color.red);
g.drawRect(10, 10, sz.width-20, sz.height-20);
// Illustrate 2d primitives
Graphics2D g2;
g2 = (Graphics2D) g;
g2.setRenderingHints(Graphics2D.ANTIALIASING, Graphics2D.ANTIALIAS_ON);
// make the box at 125, 125 that's 200 x 100 pixels
GeneralPath p = makeBox(sz.width/4, sz.height/4,
200, 100);
p.setWindingRule(GeneralPath.EVEN_ODD);
AffineTransform tfm = new AffineTransform();
// now translate it by 125, 125 so it appears at the center
tfm.translate(sz.width/4, sz.width/4);
g2.setTransform(tfm);
g2.setColor(Color.blue);
g2.fill(p);
tfm = new AffineTransform();
p = makeBox(sz.width/4, sz.height/4, 200, 100);
// now translate it by -125, -125 so it appears centered at 0,0
tfm.translate(-sz.width/4, -sz.width/4);
g2.setTransform(tfm);
g2.setColor(Color.green);
g2.draw(p);
// transform the shape so now we have it centered at the origin
Shape s = p.createTransformedShape(tfm);
// now create a transform that's translated to the center of the
// screen and rotated counter-clock-wise by 30 degrees
tfm = new AffineTransform();
tfm.translate(sz.width/2, sz.width/2);
tfm.rotate(-Math.PI/6);
g2.setTransform(tfm);
g2.setColor(Color.red);
g2.draw(s);
}
public void test4(Graphics g) {
Dimension sz = getSize();
g.setColor(Color.red);
g.drawRect(10, 10, sz.width-20, sz.height-20);
// Illustrate 2d primitives
Graphics2D g2;
g2 = (Graphics2D) g;
g2.setRenderingHints(Graphics2D.ANTIALIASING, Graphics2D.ANTIALIAS_ON);
// create the magic transform :)
AffineTransform tfm = new AffineTransform(1.0, 0.0,
0.0, -1.0,
(float)sz.width/2,
(float)sz.height/2);
AffineTransform tfm1 = new AffineTransform();
g2.setTransform(tfm);
g2.setColor(Color.red);
GeneralPath p = makeCross(25, 25, 8);
g2.draw(p);
p = makeCross(-100, 25, 8);
g2.draw(p);
p = makeLine(0, 0, 200, 0);
g2.draw(p);
p = makeLine(0, 0, 0, 200);
g2.draw(p);
Point2D pt1 = new Point2D.Double(30.0, 25.0);
Point2D pttfm1 = tfm.transform(pt1, null);
Point2D pt2 = new Point2D.Double(-105.0, 25.0);
Point2D pttfm2 = tfm.transform(pt2, null);
// If you comment out the following four lines, and uncomment
// the lines below, you'll see slower and really funny drawString
// operation. (i.e. since the original transform is in effect
// you'll see the text drawn flipped along the y-axis as well!)
g2.setTransform(tfm1);
g2.setColor(Color.black);
g.drawString("25,25", (int) pttfm1.getX(), (int) pttfm1.getY());
g.drawString("-100,25", (int) pttfm2.getX(), (int) pttfm2.getY());
// This is much slower
// g2.drawString("25,25",(float) pttfm1.getX(), (float) pttfm1.getY());
// g2.drawString("-100,25",(float)pttfm2.getX(),(float) pttfm2.getY());
}
public void paint(Graphics g) {
switch (testNumber) {
default:
case 1: test1(g); break;
case 2: test2(g); break;
case 3: test3(g); break;
case 4: test4(g); break;
}
}
public void initialize(String args[]) {
int testNum = 1;
WindowListener l = new WindowAdapter() {
public void windowClosing(WindowEvent e) {System.exit(0);}
public void windowClosed(WindowEvent e) {System.exit(0);}
};
if (args.length == 1) {
try {
testNum = Integer.valueOf(args[0]).intValue();
} catch (Exception e) {
System.err.println(e.toString());
}
}
Frame f = new Frame("2D Demo ...");
f.addWindowListener(l);
f.add("Center", new Test2D(testNum));
f.pack();
f.setSize(new Dimension(500,500));
f.show();
}
public static void main(String args[]) {
Test2D t = new Test2D(1);
t.initialize(args);
}
}
Page 2 of 2
This article was originally published on February 5, 1998