CUPS - How do I set gamma correction globally?

["Phillip Deackes" <gsmh@gmx.co.uk>]

I have just installed CUPS and it works very well on my laser printer (Brother
HL-1050, using HP laserjet driver). I would like to add gamma correction
though. On the command line, I do 'lpr -o gamma=2000 filename' and the result
is much more to my liking. How can I get this to work globally without having
to print from the command line each time? I had a look in the various CUPS
config files and I can't see where it could be added.

TIA.

-- 
Phillip Deackes
Using Storm Linux 2000