Re: [java2d] Graphics 2D

[Jim Graham]

> I want to draw two Ellipses on different direction(eg, the anger between the
> two axises is 40 degree).
> Does the Graphics2D provides a simple way to solve the problem?

You can create an Ellipse2D object with perpendicular axes and then
transform it with a shearing transform to produce a sheared ellipse
with axes at a different angle:

        Ellipse2D ellipse = new Ellipse2D.Double(x, y, w, h);
        AffineTransform at = new AffineTransform();
        at.shear(Math.tan(Math.toRadians(90 - angle)), 0);
        Shape s = at.createTransformedShape(ellipse);

Attached is a small test program to show this...

                                ...jim

import java.awt.*;
import java.awt.geom.*;
import java.awt.event.*;

public class Ellipsoid extends Canvas {
    int angle = 90;

    public Dimension getPreferredSize() {
        return new Dimension(400, 400);
    }

    public void paint(Graphics g) {
        // Code to create skewed Ellipse
        Ellipse2D ellipse = new Ellipse2D.Double(-50, -100, 100, 200);
        AffineTransform at = new AffineTransform();
        at.shear(Math.tan(Math.toRadians(90 - angle)), 0);
        Shape s = at.createTransformedShape(ellipse);
        // End code to create skewed Ellipse

        // Code to illustrate results
        Graphics2D g2d = (Graphics2D) g;
        g2d.setColor(Color.white);
        g2d.drawString("Angle = "+angle, 10, 20);
        g2d.setStroke(new BasicStroke(3));
        g2d.translate(200, 200);
        g2d.setColor(Color.blue);
        g2d.fill(s);
        g2d.setColor(Color.green);
        g2d.draw(s);
        g2d.transform(at);
        g2d.setColor(Color.red);
        g2d.drawLine(-50, 0, 50, 0);
        g2d.drawLine(0, -100, 0, 100);
    }

    public void newAngle(int ang) {
        this.angle = ang;
        repaint();
    }

    public static void main(String argv[]) {
        Frame f = new Frame();
        f.addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) { System.exit(0); }
        });
        final Ellipsoid ell = new Ellipsoid();
        Scrollbar sb = new Scrollbar(Scrollbar.HORIZONTAL, 90, 10, 30, 160);
        sb.addAdjustmentListener(new AdjustmentListener() {
            public void adjustmentValueChanged(AdjustmentEvent e) {
                ell.newAngle(e.getValue());
            }
        });
        f.setLayout(new BorderLayout());
        f.add(ell, "Center");
        f.add(sb, "South");
        f.pack();
        f.show();
    }
}