Zach -- From what I can tell, the "xv" program does just what you want. If you don't have it on your Debian distribution, you can download it from a Debian mirror -- it's in "non-free", so it's not included on the cd's anymore (to my knowledge). There is an option under the "save" window that allows you to save a captured image as an "IRIS RGB" file. Worked just fine for me just now :-).
Hope this is what you needed ... -- Harmon