just a little drawing program. nothing fancy (surely not good code either), but something that at least entertained me for a little while, and a little history of how it was born :-)

#!perl -w

# note: should be saved as tao.pl

use strict;
use GD;
use Getopt::Long;
use vars qw( $PARTS $DIM $HELP );

GetOptions(
    'parts=i'       => \$PARTS,
    'dimension=i'   => \$DIM,
    'help!'         => \$HELP,
) or warn(qq(try "$0 --help"\n)), exit(1);


if($HELP) { print usage(); exit(0); }

$DIM   ||= 500;
$PARTS ||= 2; # zero is balance of powers anyway.

my $arcw = $DIM/$PARTS;

my $TAO = GD::Image->new($DIM, $DIM);

my $yin  = $TAO->colorAllocate(0x00, 0x00, 0x00);
my $yang = $TAO->colorAllocate(0xFF, 0xFF, 0xFF);

my @shade = ();
foreach (0..$PARTS) {
    push(@shade, $TAO->colorAllocate(
        ( 255 * ($_+1) / ($PARTS+1) ) x 3 
    ));
}

$TAO->filledRectangle(
    0, 0, $DIM, $DIM, $yang
);

foreach my $arc (1..$PARTS) {
    $TAO->arc( 
        ($arc*$arcw)/2, $DIM/2, 
        $arc*$arcw, $arc*$arcw, 180, 0, 
        $yin
    );
}

foreach my $arc (1..$PARTS) {
    $TAO->arc( 
        $DIM-($arc*$arcw)/2, $DIM/2, 
        $arc*$arcw, $arc*$arcw, 0, 180, 
        $yin
    );
}

foreach my $arc (1..$PARTS-2) {
    $TAO->fill( 
        $arcw/2+$arc*$arcw, $DIM/2, 
        $shade[$arc-1]
    );
    $TAO->arc(
        $arcw/2+$arc*$arcw, $DIM/2, 
        $arcw/5, $arcw/5, 0, 360, 
        $shade[$PARTS-$arc-1]
    );
    $TAO->fill(
        $arcw/2+$arc*$arcw, $DIM/2, 
        $shade[$PARTS-$arc-1]
    );
}

$TAO->fill( 
    $arcw/2-$arcw/5-2, $DIM/2, 
    $yin
);
$TAO->arc( 
    $arcw/2, $DIM/2, 
    $arcw/5+1, $arcw/5+1, 0, 360, 
    $yang
);
$TAO->fill( 
    $arcw/2, $DIM/2, 
    $yang
);
$TAO->arc( 
    $DIM-$arcw/2, $DIM/2, 
    $arcw/5, $arcw/5, 0, 360, 
    $yin
);
$TAO->fill( 
    $DIM-$arcw/2, $DIM/2, 
    $yin
);

open    TAO, ">tao-$PARTS.png";
binmode TAO;
print   TAO $TAO->png();
close   TAO;

print "take a look at tao-$PARTS.png. have a nice day -- dada.\n";

sub usage { <<EOF;

$0 (c) 2003 Aldo Calpini <dada\@perl.it>

usage: $0 [OPTIONS]

options:

    -d=N (--dimension=N) width and height, in pixels, of the 
                         resulting image.
    -p=N (--parts=N)     number of parts (2 for a "regular" 
                         tao image).
    -h   (--help)        show this text.

the defaults, if OPTIONS are not specified, are:

    -d=500 -p=2

output will be saved in "tao-N.png", where N is the value of 
the -p option.

EOF
}
[download]

update: removed some silliness (just realized that $x/($x/$y) is $y).

cheers,
Aldo

King of Laziness, Wizard of Impatience, Lord of Hubris