Forum Moderators: phranque
You need to make use of a server-side scripting language like PHP, perl or ASP. Which one to use may depend on the server software hosting your site (as a general rule, (Microsoft) IIS servers are best for ASP, Apache server for PHP).
Once you've chosen a scripting language, you can then choose to have a go at writing the code yourself, or look for a pre-made option you can use.
[imagemagick.org...]