transform several pictures into one

Hello, i have a website and i need to add functions which allow the users to transform 4+ images too one and add texts but i have no idea how i can handle it... it should work like this:http://cyberimpulses.com/WordPress/Noplate/wordpress/plate-design/?product_id=3818 but only with "add pictures", "add texts" and "publish"

so my question with which methode/language i can do this?