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Re: changing contrast and brightness on the fly [message #25435 is a reply to message #25432]

Fri, 15 June 2001 19:43

david[2]
Messages: 100
Registered: June 2001

Senior Member

Simon Williams writes:

> 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.
>
> 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.
>
> It sounds easy but I can't find anything similar described on the web
> etc. to use as a suitable starting point.

Sometimes the things that sound the easiest are really
the hardest. :-)

But in this case, I think you are right. It's
fairly easy. The hard part (it seems to me) is
coming up with the appropriate equation to
go from a movement in pixel space to a change
in contract/brightness. I remember working with
Phil Williams when he was at Children's Hospital
in Cinncinatti and he had a gadget just like this.
I can't recall the equation how, but I seem to
remember it was some kind of high energy particle
field equation, or something. He had chanced upon
it from a previous life as a real physicist. Great
use for it though.

In any case, I think it is likely someone will
offer you something very like this, or at least
a better idea than I can give you. It is a
common feature of medical image processing.
I wouldn't be surprised to see the algorithm in
a medical imaging book.

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

Yes, I think this is exactly what you need to do.
If you can just find the right scaling equation...

Cheers,

David

--
David Fanning, Ph.D.
Fanning Software Consulting
Phone: 970-221-0438 E-Mail: davidf@dfanning.com
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Toll-Free IDL Book Orders: 1-888-461-0155

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[Message index]

		changing contrast and brightness on the fly By: Simon Williams on Fri, 15 June 2001 17:13
		Re: changing contrast and brightness on the fly By: david[2] on Fri, 15 June 2001 19:55
		Re: changing contrast and brightness on the fly By: david[2] on Fri, 15 June 2001 19:43
		Re: changing contrast and brightness on the fly By: Ken Mankoff on Fri, 15 June 2001 19:24
		Re: changing contrast and brightness on the fly By: Richard Tyc on Mon, 18 June 2001 07:42
		Re: changing contrast and brightness on the fly By: slashell on Thu, 21 June 2001 09:55
		Re: changing contrast and brightness on the fly By: John-David T. Smith on Wed, 20 June 2001 13:26
		Re: changing contrast and brightness on the fly By: Liam E. Gumley on Wed, 20 June 2001 07:11
		Re: changing contrast and brightness on the fly By: m.hadfield on Mon, 18 June 2001 18:41

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