Remove spaces in image names

Does anybody know of an extension or other modification that will replace spaces in image names with - or _ or somesuch other method. I need this for the several hundred images that my client has uploaded with spaces in names:

For example - change 'this brilliant image.jpg' to something like 'this-brilliant-image.jpg'.

I'm sure I have seen this somewhere but can I find it now????

Robster

Thanks for that. I did see that thread but I also am sure there was an extension created to do this in real time as well as on existing images.

Rob