I'm trying to figure out how to do what is described in the UEFA app as far as letting users select a background image to stand in front of where they're really standing in front of a green screen. I've been reading about green screen / chroma key videos and have spent a lot of time trying to Google and figure out what I need to do. However, I'm lost. My goal is the following. In a trade-show booth, set up an iPad that is pointing at a green screen. Allow the user to select some static image background, such as a field of flowers or a mountain range. Then let them take a picture with them super-imposed on that background, possibly with some cartoony birds or something flying around them. Is this possible? Do I have to shoot transparent video of the static backgrounds? Can anyone explain the process to someone who is not a videographer? Thanks in advance.