Image Forge

Mandelbrot Set, Julia Set, Fractal Planet Generator, Java Applet

This page is a Java applet container. Apologies to users of character mode browsers (I prefer Lynx :-) and those with Java disabled. You can get the source here if you like.

Please wait while the applet loads.

This is a JDK 1.1.n version of the applet. If your web browser is not new enough to support JDK 1.1.n you can try an older JDK 1.0.2 version here.

If your web browser is new enough to support Java 2 (JDK 1.2 or JDK 1.3, etc.), either internally or with a plugin, and the applet is not working, then check this note.

To start just click "New MSet" or "New Planet" and a window will appear and begin drawing an image; or click "New Window" and the window will wait for you to start the drawing, so you can set the window size or look through the menus first. For help and more information, click the "Help and About" button (or click here).

When a Mandelbrot set has finished drawing you can zoom in on the interesting parts. To zoom in just make a selection: press the mouse button at a starting point and hold it down, drag the mouse diagonally across the interesting area, and release the button at the point that completes the selection. A new image of the selected area will automatically begin. You can see the Julia set for a point in or near the Mandelbrot by single-clicking that point. The Julia can be magnified with a selection just as the Mandelbrot can, and a click on the Julia set will redraw the Mandelbrot.

There are parameters for the images which can be adjusted through dialog boxes. You can open a settings dialog by selecting the menu Image->Settings on an image window's menu bar. If you need help with the dialogs -- and many of the settings do need explanation -- click the applet's "Help and About" button.

The fractal planet generator code is an adaption of the ppmforge program that is included with the pbmplus and NetPBM raster image utilities. The license in ppmforge.c allows unrestricted use of the code. To find the NetPBM utilities look here.

The source, under the terms of the GNU GPL, is available here. Read the file COPYING in the archive.

Java 2 Note

I've belatedly found that the applet might not work with the default security profile of newer Java installations. The problem is with a thread constructor with a thread group argument. That is not permitted by default, at least with the Sun JDK 1.3.1_02 for GNU/Linux that I tested with (specifically, the libjavaplugin_oji.so under Mozilla 0.9.9).

Barring additional problems that I did not have, you can make the applet work by adding



grant codeBase "http://www.ehynan.com/java_applet/fractal_applet/FractApplet/" {
  permission java.lang.RuntimePermission "modifyThreadGroup";
};

to the user or global policy file (and I expect the former is preferable to the latter). You will of course need to know which file to edit. The details can be found at http://java.sun.com/j2se/1.3/docs/guide/security/permissions.html, and the JDK (JRE too?) includes a tool to edit the user policy file (see link above).

By the way, you don't know me and it would be foolish to modify a security setting because I say it is necessary for this applet. Read the above link and use your judgment. I don't know why Sun has restricted thread group modifications by default. It was not so previously, but they might have found potential DOS attacks or the like, and made the change as a response. I say that there is no intentional mischief in the applet, but understand that I do not accept responsibility for any unexpected problem that might arise.

Comments welcome,
Ed Hynan <wadmin@example.com>

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