Create an online stencil designer plus checkout function

Create an interactive stencil designer (much like a piece of software to design a tshirt with) where website customers can design their own custom order. Designer portion should be a drag and drop style functionality and allow users to size and rotate shapes and text. Users should also be able to delete elements and start over. Once complete, the system produces a vector PDF and allows the customer to pay for it and complete the standard checkout process. I have a list of fonts and design elements to incorporate ready to go. The program must be incorporated into an existing Joomla website. We have a shopping cart called Tienda, but are willing to change to whatever we need to in order to make this work. Example of a working site for an idea of what we're talking about: [login to view URL]