A java applet that can be used to generate patterns and explore symmetry is available for
use. In particular, "edge limit" patterns, "center limit" patterns and patterns where
the foreground and background are reversible may be generated. Such patterns were made
famous by the Dutch artist M. C. Escher.
A quick understanding of the program's capabilities may be obtained by working the short
tutorial included in the help file.
The program consists of a Java applet (20 class files) and two supporting Perl scripts.
help file is included with the program. This file describes in detail the capabilities of the program
and how to use it.
The java applet is called from an html file (see Patterns.html) using the following code:
<applet code="Patterns.class" width=625 height=404>
<param name=Server value="linuxenvy.com">
<param name=UserName value="bprentice">
<param name=Directory value="Patterns">
<param name=ReadFile value="pattern">
<param name=WriteFile value="pattern">
<param name=Mail value="firstname.lastname@example.org">
<param name=Message value="A new pattern has arrived.">
The seven 'param' lines define the applet options. The value of 'Server' is the address
of your server. The value of 'UserName' should be set to your user name. If you install the program in a subdirectory of your public_html directory, set the value of 'Directory' to that subdirectory otherwise set the value of 'Directory' to "".
The program saves patterns in a pattern file. This file contains a special header.
For security reasons, the program will not create this file and will only append patterns
to an existing file containing this special header. The file is normally called pattern
and is created by making a copy of the file called header.
The values of 'ReadFile' and 'WriteFile' should normally be set to the same value pattern.
If you wish to edit a pattern file, however, set the value of 'ReadFile' to an existing
file and set the value of 'WriteFile' to the name of a new copy of the header file.
If you wish to be informed by mail when a new picture entry arrives set the value of
'Mail' to your email address and the value of 'Message' to the message that you want mailed.
Otherwise set both of these values to "".
To implement the program do the following:
Download Patterns.zip and unzip it using
WinZip. This will provide you with copies of all
- Decide on a directory to hold your program. This will typically be your
public_html directory or one of its subdirectories.
- Edit the Patterns.html file to reflect your needs paying particular attention to the
six 'param' lines which define your options.
- Upload all the 'class' files, all the 'gif' files, all the 'html' files, and the
header file to your selected directory.
- Make a copy of header and call it pattern (or the value of the WriteFile parameter if
you changed this parameter).
- Test your program.
The Perl scripts ReadPicture and WritePicture and the Patterns.html file must be changed.
Line 11 of ReadPicture and line 11 of WritePicture contain the path to the server's user
directory and should be changed to your user directory path. These two files should then be
placed in your cgi-bin directory. The value of the Server parameter of the applet call in
the file Patterns.html should be changed to your server address.
The following files are included in Patterns.zip.
You may examine and try a
The Java source code for Patterns is
the Perl source code for the ReadPicture script is
and the Perl source code for the WritePicture script is
The format of the picture file is described
- The Infinite World of M. C. Escher - Harry N. Abrams, Inc., New York 1984.
- An Implementation of the Henderson Picture Language - Lisp: A Language for
Stratified Design - By Harold Abelson and Gerald Jay Sussman - Byte February 1988
Please take a look at my
and the stand alone version of my
This program was written by Brian Prentice who may be contacted at
If you use this program please send a postcard of your home town to the following
address and if possible use an interesting stamp.
355, So 8th St., #1
Coos Bay OR 97420