images that play nicely with revision control?

[Hendrik Boom <hendrik@topoi.pooq.com>]

I'm looking for a file format for images that plays nicely with revision 
control. Ideally I'd like to edit them while seeing what I'm editing, 
whether it's a line drawing (like inkscape) or a pixel map.

And I'd like to keep the whole thing under revision control (like 
monotone, or git, or such.  Currently I use monotone).

But any kind of compressed file format is probably not going to cut it.  
Revision control seems to be designed for program text, with lots of 
newlines in stable places.

If all else fails, and I get desperate I could even store my images as 
programs in, say, Scheme or C or some such, and run the code to see the 
image.  But that would make editing difficult.  And in that case, I'd 
like recommendations to graphics libraries that can output to a variety 
of formats, such as onto the screen, into a jpeg file, to svg or html 
format, or some such.

I would definitely prefer not to write a whole new image editor from 
scratch.

-- hendrik