changing contrast and brightness on the fly

[Simon Williams <williams.simon(at)gene.com>]

Greetings,

I'm looking for tips on how to implement an image display feature that's
bugging me. I'm new to widget programming, trying to get up to speed
with David Fanning's book and other helps, but any short-cuts would be
appreciated.

The job is to display one or more grayscale MRI images (mostly small,
256 pixels squared is common) and then to be able to adjust the image
brightness and contrast interactively, without going to any special
widgets like sliders. The functionality I have in mind is to
middle-click the image and then have drag right/left control contrast
and drag up/down control brightness.

The plan is to replicate functionality that the end users (radiology
folks) are already familiar with from other image viewers.  In the
longer term plan, the display would also be re-sizable and allow
interactive ROI drawing as well.

The functionality I have in mind is to middle-click the image and then
have drag right/left control contrast and drag up/down control
brightness.

It sounds easy but I can't find anything similar described on the web
etc. to use as a suitable starting point.  Question: is changing the
(familiar to me) contrast and brightness equivalent to re-defining the
color table and re-scaling the data (more often discussed with color
images).  What parameters really define contrast and brightness? 

Thanks for any help you can offer,

Simon Williams