Add Zoom functionality to Scrollview in Ipad App

I require a quick bit of code that will allow zooming of a scrollview that I have set up containing a series of images. when the user either double taps or zooms in using gestures, that area of the page is zoomed in by 50%. When they double tap again, it is back to normal (100%) viewing resolution. It is essential that the user can continue to scroll left and right once they have restored the zoom scale to normal to carry on moving between images. Im hoping this is a quick job for an experienced iOS developer :- )