I don't remember what prompted me to do it exactly, but I started goofing off with dojox.gfx and some large images and ended up writing a Magnifier class widget, which will unobtrusively give any image on a page an overlay when you hover it, showing a zoomed version of the region you are hovering.

It is marked experimental, atm, as it is only a few days old in trunk, but give it a look anyway, and tell me what you think:

http://archive.dojotoolkit.org/nightly/checkout/dojox/image/tests/test_M...

It uses SVG for the "viewport" because I had intended to put a nice SVG surface over the overlay and do clipping making the surface rounded, but didn't get that far yet. The SVG version will probably stay dojox.image.Magnifier and a second version without dojox.gfx support will be possibly called dojox.image.MagnifierLite ... all thoughts are welcome.

Coincidentally, I wrote a similar thing in jQuery the same day: It doesn't work as well, and there is an issue I am experiencing based on lack of jQuery experience I suspect, but it works too: (not in FF/Linux, i'm told though?)

http://dojotoolkit.org/~dante/jquery/Magnifier.html

Thanks be to dmachi for helping me debug my silly calculations. ;)