Portraits in the Wizarding world after reading short stories. I don’t think I understand how portraits work. I thought that a portrait of a wizard had to be prepared by that person so that the portrait is like that person as much as possible. Is that true? 

So McGonagall put up a portrait of snape after Harry explained how he was a hero of the war. I wonder if that portrait is just a moving portrait or if it’s a representation of snape like the headmaster ones.