How do I get a picture unstuck from the glass of a frame without totally ruining it?

My boyfriend has a picture of his children when they were very young and I wanted to restore it for him for Christmas or his birthday but the picture is stuck to the frames glass and the glass is broken. I want to know how to get it unstuck without totally ruining it so that I can scan it and restore it. HEEEEELLLPPP PLEEEEEEZ!!!!