image filter

[nic-del]

Hi, hoping someone may be able to help... if I'm in the wrong forum I apologise bt I've been racking my brain for the best way to do this and thought JS may be the best...

I have 2 identical images, one is a full color image, the other is a black and white sketch of the other.

I'm looking to do a mouse over effect so when you hover over the sketch image the colour image fades in like a filter around the mouse area! am I making any sense, probably not. I have attached 3 images, the color image, the sketch and a idea of what I'm trying to achieve.

If anyone has any idea it would be much very appreciated!

Thanks

[jscheuer1]

Here is something close, IE only:

http://www.dynamicdrive.com/dynamicindex4/spotlight.htm