Scaling an image to square

I'm looking to add 75px square thumbnails while keeping the aspect ratio of the image. However I don't just want the image scaled down I also want it cropped so it fills the entire box.

So for an example this image


would turn into this thumbnail


I've seen a working example of this at Echopic (you need to be registered to see it in aciton)

Any help would be appreciated.

 

you can see here a very nice example
http://www.findmotive.com/2006/12/13/php-crop-image/

 

Kindly have a look at

http://www.gen-x-design.com/projects/php-thumbnailer-class/
http://joanpiedra.com/jquery/thumbs/