Crop images and composing them

Sandro <[email protected]> Fri, 01 Apr 2011 18:05:00 +0200

Newsgroups	gmane.comp.video.image-magick.user
Message-ID	<[email protected]>

Dear all,
I have a question. In CSS file I have this file:
http://imgby.com/close.png

is it possible to crop the first button, similar to this CSS command:
-moz-image-region: rect(0,16,16,0);
(top, right, bottom, left)

I want to obtain a 64x16 PNG adding the cropped button as fourth button.
Thanks

-moz-image-region
Sandro