[Greasemonkey] GM_xmlHttpRequest and Images

[Brendan J]

Okay, I want to make a GM script that uses the GM_xmlhttpRequest to write to
a file on the users HD.  For instance, every time a page comes up with a
specific image on it, I want to be able to save that to the HD automatically
with the GM script.  The image name will probably be the same each time, and
the specifics of making random names doesn't escape me, but what I'm having
a hard time doing is, how do I take a image on a webpage and extract its
little internal binary code into a format JS can manage, and save it to the
HD?  Is this beyond the scope of JS and GM?

Thanks,

Brendan