thumbnails.pl

!/usr/bin/perl -w
use strict;
use warnings;
use utf8;

#compiled from source like: http://www.imagemagick.org/script/perl-magick.php
use Image::Magick;

#rock through the directory index
my @files = <*.{jpg,jpeg,png,gif}>;

#print little thumbnails of all the images
foreach my $file (@files) {
  my $image = Image::Magick->new();
  $image->Read($file);
  $image->Resize('450x150');
  $image->Write(".t_$file");
  print "<a href=\"$file\"><img src=\".t_$file\"></a>\n";
}

./thumbs > thumbnails.html

Thumbnails are named .t_filename.extension to be hidden from Apached directory index but still available to download. This may not work if your server refuses to serve files beginning with "." but it's quite tidy.