The main point of this zoom application is that when you zoom the image will take up the full area available of it's container.
It also supports changing the image dynamically with the newpic() function.
It's pretty simple, but I couldn't find a nice alternative so I just wrote one.
It's built on top of Jquery and Jquery UI - you only need draggable from UI for this. It's made mobile friendly by using jQuery UI Touch Punch.
The sample image from Wikipedia: https://commons.wikimedia.org/wiki/File:Italy-Taormina-Macro_Flower_-_Creative_Commons_by_gnuckx_%283206953695%29.jpg