Compliment or Cover Up?

How can you tell the difference on whether someone thinks your attractive or they're just trying to spare your feelings?

ie.

Person 1: "You look terrible in this photo."
Person 2: "Excuse me?"
Person 1: "What...oh no, I mean, you don't usually but, this photo is just...I mean, you're great looking and all...not that I was looking...not that there's anything WRONG with looking at you... I'll shut up now."

It's a typical type of conversation I hear around my class.

sounds like a covered up compliment

Is that me or Jackie, Carly?

*Insert witty Bert-like comment here*