Android Question Move imageview (Center Crop)

Hi all i make a center crop in my app and i have one question

i see this on many apps but i dont have any ideia how to make this xD

FOR EXAMPLE



1 big image and user can move this image



user can only move the image but dont change the crop
how its possible make this ? *-*

how to make a user movimentation zoom + -

like this




here is my crop