An introduction to the Java 2D API

February 5, 1998
By Sundar Narasimhan

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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);
    }
}