Mega Code Archive
A Swing component that computes and displays a fractal image known as a Julia set
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/*
* Copyright (c) 2004 David Flanagan. All rights reserved.
* This code is from the book Java Examples in a Nutshell, 3nd Edition.
* It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied.
* You may study, use, and modify it for any non-commercial purpose,
* including teaching and use in open-source projects.
* You may distribute it non-commercially as long as you retain this notice.
* For a commercial use license, or to purchase the book,
* please visit http://www.davidflanagan.com/javaexamples3.
*/
//package je3.print;
import java.awt.Component;
import java.awt.Dimension;
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.JobAttributes;
import java.awt.PageAttributes;
import java.awt.PrintJob;
import java.awt.Toolkit;
import java.awt.image.BufferedImage;
import javax.swing.JComponent;
/**
* This class is a Swing component that computes and displays a fractal image
* known as a "Julia set". The print() method demonstrates printing with the
* Java 1.1 printing API, and is the main point of the example. The code that
* computes the Julia set uses complex numbers, and you don't need to understand
* it.
*/
public class JuliaSet1 extends JComponent {
// These constants are hard-coded for simplicity
double x1 = -1.5, y1 = -1.5, x2 = 1.5, y2 = 1.5; // Region of complex plane
int width = 400, height = 400; // Mapped to these pixels
double cx, cy; // This complex constant defines the set we display
BufferedImage image; // The image we compute
// We compute values between 0 and 63 for each point in the complex plane.
// This array holds the color values for each of those values.
static int[] colors;
static { // Static initializer for the colors[] array.
colors = new int[64];
for (int i = 0; i < colors.length; i++) {
colors[63 - i] = (i * 4 << 16) + (i * 4 << 8) + i * 4; // grayscale
// (i*4) ^ ((i * 3)<<6) ^ ((i * 7)<<13); // crazy technicolor
}
}
// No-arg constructor with default values for cx, cy.
public JuliaSet1() {
this(-1, 0);
}
// This constructor specifies the {cx,cy} constant.
// For simplicity, the other constants remain hardcoded.
public JuliaSet1(double cx, double cy) {
this.cx = cx;
this.cy = cy;
setPreferredSize(new Dimension(width, height));
computeImage();
}
// This method computes a color value for each pixel of the image
void computeImage() {
// Create the image
image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
// Now loop through the pixels
int i, j;
double x, y;
double dx = (x2 - x1) / width;
double dy = (y2 - y1) / height;
for (j = 0, y = y1; j < height; j++, y += dy) {
for (i = 0, x = x1; i < width; i++, x += dx) {
// For each pixel, call testPoint() to determine a value.
// Then map that value to a color and set it in the image.
// If testPoint() returns 0, the point is part of the Julia set
// and is displayed in black. If it returns 63, the point is
// displayed in white. Values in-between are displayed in
// varying shades of gray.
image.setRGB(i, j, colors[testPoint(x, y)]);
}
}
}
// This is the key method for computing Julia sets. For each point z
// in the complex plane, we repeatedly compute z = z*z + c using complex
// arithmetic. We stop iterating when the magnitude of z exceeds 2 or
// after 64 iterations. We return the number of iterations-1.
public int testPoint(double zx, double zy) {
for (int i = 0; i < colors.length; i++) {
// Compute z = z*z + c;
double newx = zx * zx - zy * zy + cx;
double newy = 2 * zx * zy + cy;
zx = newx;
zy = newy;
// Check magnitude of z and return iteration number
if (zx * zx + zy * zy > 4)
return i;
}
return colors.length - 1;
}
// This method overrides JComponent to display the julia set.
// Just scale the image to fit and draw it.
public void paintComponent(Graphics g) {
g.drawImage(image, 0, 0, getWidth(), getHeight(), this);
}
// This method demonstrates the Java 1.1 java.awt.PrintJob printing API.
// It also demonstrates the JobAttributes and PageAttributes classes
// added in Java 1.3. Display the Julia set with ShowBean and use
// the Command menu to invoke this print command.
public void print() {
// Create some attributes objects. This is Java 1.3 stuff.
// In Java 1.1, we'd use a java.util.Preferences object instead.
JobAttributes jattrs = new JobAttributes();
PageAttributes pattrs = new PageAttributes();
// Set some example attributes: monochrome, landscape mode
pattrs.setColor(PageAttributes.ColorType.MONOCHROME);
pattrs.setOrientationRequested(PageAttributes.OrientationRequestedType.LANDSCAPE);
// Print to file by default
jattrs.setDestination(JobAttributes.DestinationType.FILE);
jattrs.setFileName("juliaset.ps");
// Look up the Frame that holds this component
Component frame = this;
while (!(frame instanceof Frame))
frame = frame.getParent();
// Get a PrintJob object to print the Julia set with.
// The getPrintJob() method displays a print dialog and allows the user
// to override and modify the default JobAttributes and PageAttributes
Toolkit toolkit = this.getToolkit();
PrintJob job = toolkit.getPrintJob((Frame) frame, "JuliaSet1", jattrs, pattrs);
// We get a null PrintJob if the user clicked cancel
if (job == null)
return;
// Get a Graphics object from the PrintJob.
// We print simply by drawing to this Graphics object.
Graphics g = job.getGraphics();
// Center the image on the page
Dimension pagesize = job.getPageDimension(); // how big is page?
Dimension panesize = this.getSize(); // how big is image?
g.translate((pagesize.width - panesize.width) / 2, // center it
(pagesize.height - panesize.height) / 2);
// Draw a box around the Julia Set and label it
g.drawRect(-1, -1, panesize.width + 2, panesize.height + 2);
g.drawString("Julia Set for c={" + cx + "," + cy + "}", 0, -15);
// Set a clipping region
g.setClip(0, 0, panesize.width, panesize.height);
// Now print the component by calling its paint method
this.paint(g);
// Finally tell the printer we're done with the page.
// No output will be generated if we don't call dispose() here.
g.dispose();
}
}
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