Combining an uploaded image with an image imported from php

Project Description:
We need an online solution that will allow us to combine two images with the following process:

1. Set a variety of canvas sizes, from business card to A4, plus a user defined canvas size.
2. Upload a background image on the canvas
3. Position and resize the background image, with an option to prevent distortion of the image, for example hold down shift key.
4. Import a second image from a php database over the top of the background
5. Position and resize the top image. Resizing the top image must prevent any distortion at all times.
6. Export the combined images as JPG, PNG, PDF

Users should preferably be able to store a number of canvases and background images as templates, to make it easy to re-run the job again.

Please contact me, so we can discuss further.