contrast/brightness adjusting in iceweasel

[Paul E Condon <pecondon@mesanetworks.net>]

I use iceweasel on my etch desktop system for internet browsing.
There are pictures on almost every web site that I visit. 
Most are just fine to view, but some (enough to be annoying) are
too dark to be view usefully. I can make out that the image is
not a uniform black, but hardly anything more.

I know that this is probably not an iceweasel problem, but rather
a problem with some library that iceweasel uses for image rendering
or a problem with Xwindows (for which I use Xorg).

Questions:

1 how do I determine what image rendering software is actually
being used by iceweasel? Does it matter?

2 is there some package that will give me some GUI controls in
iceweasel that allow adjustment of brightness/contrast on individual
images?

What further info do I need to give?

-- 
Paul E Condon           
pecondon@mesanetworks.net