One of the API's that I explored was FD Toys' Trading Card Maker. It seemed a little inflexible to me, especially since I just recently got an iPhone and it seems crazily intuitive and flexible. Nevertheless, it wasn't unenjoyable to put a picture of myself onto a trading card. I would have liked to chop off the bottom. Alas.
Mapr also seemed cool. There are a lot of things that could be fun about this. One idea that popped into my head was to find pictures of places I'd visited in order to create a kind of geographical ID. Haven't gotten to that yet.
8 years ago