How do crypto-like software display large bytes as a graphic?

Question

E.g: On apps like Metamask or Myetherwallet, it often displays the user's public address in a graphic, like some randomised drawing. What is this called and how does one do this?

Answer 1

You're probably talking about blockies. They're a specific variant of the more general idea of "identicons," which use a seed of some sort to generate an icon.