Giving shopping plugin an image URI to upload canvas along w consumer info

I have an online business I’m trying to start and it involves taking a photo of the user in browser. I do some canvas stuff using JS, then the image is meant to be saved to a server (alongside a payment ID, etc) and turned into a commodity to ship to the consumer. I have all the constituent parts working, but I’m trying to get a handle on the best workflow for the shopping connection.