Image Generation from Form Data

Script needed that will take multiple inputs from an HTML input form and generate a single image from it. The input will be mixed: the user can select a background base image, other smaller images to layer on top of the base image, and text to be added on top of the base image. Customizable position of smaller images and text onto the base image is a must. Think of a pool rules sign - but with the ability to customize the background, additional images, and customize how many and what rules are displayed. The script should be able to compile all these inputs into a single image for the user to review or make changes to with the same input form. Script must be compatible with main browsers (IE, Firefox, Safari, etc.), and clear to read and customize. Comments are a must. Code language is not specified, but must be common and easy to understand and customize. I am looking for the script to generate the image, the form code is not necessary. Let me know if you have questions!