ImageMagick has fairly detailed online documentation for the Perl bindings to their libraries. If you go here, you can see all available options and sample scripts to reach certain effects.

Untested, and out of the blue I could think of the following script:

#!/usr/bin/perl -w

use strict;
use Image::Magick;

my($image);

$image = new Image::Magick;
$image->Read('my_original.bmp');
$image->Quantize(treedepth => 24);
open(IMAGE, ">my_output.bmp");
$image->Write(file=>\*IMAGE, filename=>"my_output.bmp");
close(IMAGE);
[download]

Did I already say it isn't tested? :-)

Success,

-- JaWi

"A chicken is an egg's way of producing more eggs."