I would appreciate the thoughts of any javascript / css ninjas on how I can customise:
https://github.com/jdbartlett/loupe/blob/master/jquery.loupe.js
To have a circular zoom area instead of rectangular one? There is an option to set a css class for the loupe.
Please note that this is a question about the library linked above. I have already googled for other libraries. I want to keep the js as small as possible.
From the developer of loupe.js:
you may want to look at chris iufer's loupe, which is only a bit bigger than mine and includes a few samples that use css3 to achieve a round loupe:
http://chrisiufer.com/loupe/sample.html
whereas mine uses an absolutely positioned image within a div, his uses background-image on the div and background-position to move the image, so css3 border-radius works.