picture impression

When you see somebody on a pictures only and judge the person attitude/character, though you never met her/him in real life.

Short:
Judge people without knowing them with only a picture of them.

Johnny : Hey man, look at this girl. What an ugly cow, geez. I bet she is a real pain in as a gf

Peter : What? That's is Janine, my cousin. She is a nice person. You and your worthless picture impressions!