The web backend requires to have a PHP scripting engine running on
your web server. 

There are two scripts doing the scaling work. convert/imgconv is a plain
bash script using Imagemagick to generate thumbnails and scaling images.
You can get Imagemagick at http://www.imagemagick.org/.

# UPDATES #

* netpbm
  ------
   You can use netpbm tools instead of ImageMagick for better speed. You can
   grab netpbm at http://sourceforge.net/projects/netpbm/ but ususally your
   distro ships with it already. My YDL distro has all the toos in netpbm-progs
   package.

* webgallery.pl
  -------------

   Tuomas Kuosmannen created a nautilus script that operates on selection
   of images. It's way cooler than the bash script. Because the operation
   can take a while, it has a nifty progressbar. The script itself is in
   Perl, so you obviously need a functiuoning installation of Perl. For the
   progressbar to work, you need gtk-perl bindings. You can get them at
   ftp://ftp.gtk.org. Nautilus is a GUI file manager that rocks for photo
   management. you can grab it at http://www.eazel.com.

* webgallery-zenity.pl
  --------------------

   I hacked up Tuomas' script to use only gnome's zenity for the progress bars,
   so there's no more gtk-perl dependency. Also this script uses Larry Ewing's
   cool gdk-pixbuf scaler. It is an alternative to ImageMagick's convert
   (sharing the basic commandline parameters) that discards EXIF information
   (yet), but is 5 to 8 times as fast. You can really tell on large galleries.
   You can find both at the convert/ directory. Instructions how to compile
   gdk-pixbuf-convert.c are included in the file header.
   

If you wan't to have advanced EXIF information for your photos, make sure you
use a recent ImageMagick so that convert doesn't throw away this info when
scaling down. You also need EXIF support in your PHP.