Java 绘制环形的文字 (Circle Text Demo)

1. [代码]CircleTextDemo.java     
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
 
/**
 * A demo class that illustrates drawing text
 * along the outside of a circle.
 */
public class CircleTextDemo extends Canvas {
    Frame myframe;
    TextField text;
    Button printBtn;
    Font myfont;
    Color textcolor;
    Color circlecolor;
    
    /**
     * Create a CircleTextDemo canvas and frame
     * with default settings.
     */
    public CircleTextDemo() {
        this("Serif", Font.PLAIN, 18, Color.pink, Color.black);
    }
 
    /**
     * Create a CircleTextDemo canvas and frame
     * with supplied settings.
     *
     * @param ff Font family (usually "Serif")
     * @param fs Font style (usually Font.PLAIN)
     * @param fz Font size (usually 18)
     * @param bg Background color for this canvas (usually pink)
     * @param fg Foreground color for text (usually black)
     */
    public CircleTextDemo(String ff, int fs, int fz, Color bg, Color fg) {
        setBackground(bg);
        circlecolor = bg.brighter();
        textcolor = fg;
        myfont = new Font(ff, fs, fz);
 
        text = new TextField("Text on a circle using Java 2D Graphics!");
        myframe = new Frame("CircleTextDemo");
   printBtn = new Button("Print");
        myframe.add(text, BorderLayout.NORTH);
        myframe.add(this, BorderLayout.CENTER);
   myframe.add(printBtn, BorderLayout.SOUTH);
        myframe.setSize(new Dimension(300,340));
        myframe.setLocation(150,140);
        myframe.addWindowListener(new WindowAdapter() {
                public void windowClosing(WindowEvent we) {
                    System.exit(0);
                }
            });
        text.addActionListener(new ActionListener() {
                public void actionPerformed(ActionEvent ae) {
                    repaint();
                }
            });
   printBtn.addActionListener(new FramePrinter(myframe));
        myframe.setVisible(true);
    }
        
    /**
     * Paint the contents of the CircleDemoText canvas.
     *
     * @param g - a Graphics, hopefully a Graphics2D
     */
    public void paint(Graphics g) {
        String st = text.getText();
        if (st.length() == 0) return;
        if (g instanceof Graphics2D) {
            Dimension cd = getSize();
            Point pt = new Point(cd.width / 2, cd.height / 2);
            int radius = (int)(pt.x * 0.84);
            g.setColor(circlecolor);
            g.drawArc(pt.x - radius, pt.y - radius,
                      radius*2-1, radius*2-1,
                      0, 360);
            g.setColor(textcolor);
            g.setFont(myfont);
            drawCircleText((Graphics2D)g, st, pt, radius, -Math.PI/2, 1.0);
        }
        else {
            System.out.println("Cannot draw curved text without a Graphics2D");
        }
    }
        
    /**
     * Draw a piece of text on a circular curve, one
     * character at a time.  This is harder than it looks...
     *   
     * This method accepts many arguments:
     *   g - a Graphics2D ready to be used to draw,
     *   st - the string to draw,
     *   center - the center point of the circle (Point),
     *   r - the radius of the circle,
     *   a1 - the beginning angle on the circle to start, in radians,
     *   af - the angle advance factor (usually 1.0)
     */
    static void drawCircleText(Graphics2D g, String st, Point center,
                               double r, double a1, double af)
    {
        double curangle = a1;
   double curangleSin;
        Point2D c = new Point2D.Double(center.x, center.y);
        char ch[] = st.toCharArray();
        FontMetrics fm = g.getFontMetrics();
        AffineTransform xform1, cxform;
        xform1 = AffineTransform.getTranslateInstance(c.getX(),c.getY());
        for(int i = 0; i < ch.length; i++) {
            double cwid = (double)(getWidth(ch[i],fm));
            if (!(ch[i] == ' ' || Character.isSpaceChar(ch[i]))) {
                cwid = (double)(fm.charWidth(ch[i]));
                cxform = new AffineTransform(xform1);
                cxform.rotate(curangle, 0.0, 0.0);
                String chstr = new String(ch, i, 1);
                g.setTransform(cxform);
                g.drawString(chstr, (float)(-cwid/2), (float)(-r));
            }
 
            // compute advance of angle assuming cwid<             if (i < (ch.length - 1)) {
                double adv = cwid/2.0 + fm.getLeading() + getWidth(ch[i + 1],fm)/2.0;
      // Use of atan() suggested by Michael Moradzadeh
                curangle += Math.atan(adv / r);
      // Original code was:
      // curangle += Math.sin(adv / r);
 
            }
        }
    }
 
    /**
     * Get the width of a given character under the
     * specified FontMetrics, interpreting all spaces as
     * en-spaces.
     */
    static int getWidth(char c, FontMetrics fm) {
        if (c == ' ' || Character.isSpaceChar(c)) {
            return fm.charWidth('n');
        }
        else {
            return fm.charWidth(c);
        }
    }
 
    public static void main(String args[]) {
        CircleTextDemo ctd;
        ctd = new CircleTextDemo();
    }
 
    class FramePrinter implements ActionListener {
   private Frame fr;
   public FramePrinter(Frame f) { fr = f; }
   public void actionPerformed(ActionEvent ae) {
       PrintJob pjob;
       pjob = fr.getToolkit().getPrintJob(fr,
          "Printing Circle Demo", null, null);
       if (pjob != null) {
      Graphics g = pjob.getGraphics();
      if (g != null) {
          g.translate(100,100);
          fr.printAll(g);
          g.dispose();
      }
      pjob.end();
       }
   }
    }
 
}