Generating a mandelbrot with Java

[Mads Nielsen]

Hello.

First of all, thanks for all the replies on my other posts. I really appriciate it.

I have recently become totally facinated with fractals, and i want to make one with Java.

I have based the code on the pseudocode from the wiki article on en.wikipedia.org about mandelbrot sets.

Here is the pseudocode:

For each pixel on the screen do:
{
x0 = scaled x coordinate of pixel (must be scaled to lie somewhere in the interval (-2.5 to 1)
y0 = scaled y coordinate of pixel (must be scaled to lie somewhere in the interval (-1, 1)
x = 0
y = 0
iteration = 0
max_iteration = 1000
while ( x*x + y*y < 4 AND iteration < max_iteration ) //Remember: 4 == (2*2)
{
xtemp = x*x - y*y + x0
y = 2*x*y + y0
x = xtemp
iteration = iteration + 1
}
color = iteration
plot(x0,y0,color)
}

And this is my attempt to port it to Java:

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.Random;
public class Peach extends JPanel {
public void paintComponent(Graphics g) {
super.paintComponent(g);
this.setBackground(new Color(50, 50, 50));
int canvasSize = (800 * 600);
int x;
int y;
int x0;
int y0;
int iteration;
int max_iteration;
int color;
for(int i = 0; i < canvasSize; i++) {
x0 = 1; //Scaled x coordinate of pixel (must be scaled to lie somewhere in the interval (-2.5 to 1)
y0 = 1; //Scaled y coordinate of pixel (must be scaled to lie somewhere in the interval (-1, 1)
x = 0;
y = 0;
iteration = 0;
max_iteration = 1000;
g.setColor(new Color(100,81,215));
int xtemp;
while(x * x + y * y < 4 && iteration < max_iteration) {
xtemp = x * x - y * y + x0;
y = 2 * x * y + y0;
x = xtemp;
iteration = iteration + 1;
}
//If iteration == max_iteration then set color = black
//Else set color to something from the color palette array
color = iteration;
g.fillRect(x0, y0, 2, 2);
}
}
}

There are currently no compile or runtime errors, but its not working. Its only plotting 1 pixel. I need to scale the values for x0 and y0, so they have the range (-2.5 to 1) and (-1 to 1)
I have no idea how to do this, also, the x and y variables are integers, how am i supposed to add or multiply with double x0 and y0 ?

And i also dont understand why x0 and y0 are used as the cordinates for the plotting, i mean it has to be integers, not doubles, there are no "half pixels".

Does anyone here have experience with generating fractals using Java?

Kind regards Mads Nielsen

[Tim Moores]

For starters, there shouldn't be a loop from 1 to canvasSize, but two nested loops for 1<=x<=800 and 1<=y<=600, so that you know for which pixel the iteration depth is being calculated, and so you can set that pixel in the appropriate color. (The code is not even using "i" anywhere.)

[Tarun Bolla]

 

Mads Nielsen wrote:

x0 = 1; //Scaled x coordinate of pixel (must be scaled to lie somewhere in the interval (-2.5 to 1)
y0 = 1; //Scaled y coordinate of pixel (must be scaled to lie somewhere in the interval (-1, 1) 

In your code you hardcoded x0, y0 as 1,1. That shouldnt be the case .. You should be iterating over each and every pixel from the screen (I mean your window area) and that each pixel will provide value for x0, y0
For Eg., (As Tim said)

for(i in 0..800)
for(j in 0..600)
x0 = i scaled to be in between (-2.5 to 1)
y0 = j scaled to be in between (-1, 1)
....rest of the logic here