allow transform

This is rather rough...
To avoid adding dependencies, I added a transform parameter, where the proper prefixed name for the transform (or false) must be supplied outside of the code.

Also, the focusPoint settings where not available in the adjustFocus function, so I simply added them as parameters, I'm sure that's not a good jQuery pattern.
Someone knowledgeable on jQuery plugin options and settings patterns better take a look at this.

But it is a proof of concept that the formula is good...

Note that the transform % are expressed in relation to the image size while the left/top % are expressed in relation to the container size.