Re: changing contrast and brightness on the fly

[Ken Mankoff <mankoff(at)I.HATE.SPAM.cs.colorado.edu>]

>
> 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 an MRI image and to be able to adjust the image
> brightness and contrast interactively, without going to any special
> widgets like sliders. The control I have in mind is to
> middle-click the image and then have drag right/left control contrast
> and drag up/down control brightness.
>

I think brightness adjustment is achieved with alpha channels. May require
IDL Object Graphics.  There are other ways. Search the groups.google.com
archive for recent threads on this topic.

IDL> ? cursor ; for your
IDL> ? !mouse ; second question.

> 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
> contrast and brightness to be achieved by re-defining the
> color table and re-scaling the data?

your choice to use data or color scale. use bytscl(), lt & gt to rescale
the data. Probably easier (for debugging too) to do it on data.

-k.

-- 
Ken Mankoff
LASP://303.492.3264
http://lasp.colorado.edu/~mankoff/