I find this to be a basic necessity for a hand note app. Wacom Bambo does this well, but the program itself cannot compare to the ecology of penultimate / evernote. I use penultimate for exactly the same thing, photos from meeting sessions. I may just want a quick data plot from a white board and not the surrounding scribbles on the white board.
My suggestion: when a photo is currently placed, it has the four corner handles for resize, add another small icon that lets users change the resize handles to crop handles. Masking out crop feature would be nice, but may be over kill. I would app