fractal.txt

实现二维基本图元直线段生成的基本算法（DDA

程序代码:
/* 
* @(#)fractal.java - Fractal Program Mandelbrot Set 
* www.eckhard-roessel.de
* Copyright (c) Eckhard Roessel. All Rights Reserved.
* 06/30/2000 - 03/29/2000
*/
import java.awt.*;
import java.applet.*;
import java.awt.event.*;
/** 
* @version 1.1
* @author Eckhard Roessel
* @modified 03/29/2001
*/
public class fractal extends Applet implements MouseListener, MouseMotionListener
{ 
private final int MAX = 256; // max iterations
private final double SX = -2.025; // start value real
private final double SY = -1.125; // start value imaginary
private final double EX = 0.6; // end value real
private final double EY = 1.125; // end value imaginary
private static int x1, y1, xs, ys, xe, ye;
private static double xstart, ystart, xende, yende, xzoom, yzoom;
private static boolean action, rechteck, fertig;
private static float xy;
private Image bild;
private Graphics g1;
private Cursor c1, c2;

public void init() // all instances will be prepared
{
fertig = false;
addMouseListener(this);
addMouseMotionListener(this);
c1 = new Cursor(Cursor.WAIT_CURSOR);
c2 = new Cursor(Cursor.CROSSHAIR_CURSOR);
x1 = getSize().width;
y1 = getSize().height;
xy = (float)x1 / (float)y1;
bild = createImage(x1, y1); 
g1 = bild.getGraphics();
fertig = true;
}

public void destroy() // delete all instances 
{
if (fertig)
{
removeMouseListener(this);
removeMouseMotionListener(this);
bild = null;
g1 = null;
c1 = null;
c2 = null;
System.gc(); // garbage collection
}
}

public void start()
{
action = false;
rechteck = false;
startwerte();
xzoom = (xende - xstart) / (double)x1;
yzoom = (yende - ystart) / (double)y1;
mandelbrot();
}

public void stop()
{
}

public void paint(Graphics g)
{
update(g); 
}

public void update(Graphics g)
{
g.drawImage(bild, 0, 0, this);
if (rechteck)
{
g.setColor(Color.white);
if (xs < xe)
{
if (ys < ye) g.drawRect(xs, ys, (xe - xs), (ye - ys));
else g.drawRect(xs, ye, (xe - xs), (ys - ye));
}
else
{
if (ys < ye) g.drawRect(xe, ys, (xs - xe), (ye - ys));
else g.drawRect(xe, ye, (xs - xe), (ys - ye));
}
}
}

private void mandelbrot() // calculate all points
{
int x, y;
float h, b, alt = 0.0f;

action = false;
setCursor(c1);
showStatus("Mandelbrot-Set will be produced - please wait...");
for (x = 0; x < x1; x+=2)
for (y = 0; y < y1; y++)
{
h = punktfarbe(xstart + xzoom * (double)x, ystart + yzoom * (double)y); // color value
if (h != alt)
{
b = 1.0f - h * h; // brightnes
g1.setColor(Color.getHSBColor(h, 0.8f, b));
alt = h;
} 
g1.drawLine(x, y, x + 1, y);
}
showStatus("Mandelbrot-Set ready - please select zoom area with pressed mouse.");
setCursor(c2);
action = true;
}

private float punktfarbe(double xwert, double ywert) // color value from 0.0 to 1.0 by iterations
{
double r = 0.0, i = 0.0, m = 0.0;
int j = 0;

while ((j < MAX) && (m < 4.0))
{
j++;
m = r * r - i * i;
i = 2.0 * r * i + ywert;
r = m + xwert;
}
return (float)j / (float)MAX;
}

private void startwerte() // reset start values
{
xstart = SX;
ystart = SY;
xende = EX;
yende = EY;
if ((float)((xende - xstart) / (yende - ystart)) != xy ) 
xstart = xende - (yende - ystart) * (double)xy;
}

public void mousePressed(MouseEvent e) 
{
e.consume();
if (action)
{
xs = e.getX();
ys = e.getY();
}
}

public void mouseReleased(MouseEvent e)
{
int z, w;

e.consume();
if (action)
{
xe = e.getX();
ye = e.getY();
if (xs > xe)
{
z = xs;
xs = xe;
xe = z;
}
if (ys > ye)
{
z = ys;
ys = ye;
ye = z;
}
w = (xe - xs);
z = (ye - ys);
if ((w < 2) && (z < 2)) startwerte();
else
{
if (((float)w > (float)z * xy)) ye = (int)((float)ys + (float)w / xy);
else xe = (int)((float)xs + (float)z * xy);
xende = xstart + xzoom * (double)xe;
yende = ystart + yzoom * (double)ye;
xstart += xzoom * (double)xs;
ystart += yzoom * (double)ys;
}
xzoom = (xende - xstart) / (double)x1;
yzoom = (yende - ystart) / (double)y1;
mandelbrot();
rechteck = false;
repaint();
}
}

public void mouseEntered(MouseEvent e)
{
}

public void mouseExited(MouseEvent e)
{
}

public void mouseClicked(MouseEvent e) 
{
}

public void mouseDragged(MouseEvent e)
{
e.consume();
if (action)
{
xe = e.getX();
ye = e.getY();
rechteck = true;
repaint();
}
}

public void mouseMoved(MouseEvent e)
{
}

public String getAppletInfo()
{
return "fractal.class - Mandelbrot Set a Java Applet by Eckhard Roessel 2000-2001";
}
}