| Re: 3D histogram + sensible thresholding [message #40599 is a reply to message #40515] |
Mon, 16 August 2004 21:44  |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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Dee (nee Dorthe) writes:
>> I don't know of anything built into IDL, but it
>> would be easy to build yourself. You could easily,
>> for example, figure out how to do a 1 standard deviation
>> stretch, or something of the sort.
>
> Could that fairly easily be built into XSTRETCH?
I think it *was* built into XSTRETCH, but I took it out
because of all the people complaining about me mucking
with their data without warning them. :-)
(Actually, I think I probably do some sort of 2% linear
stretch, an idea I stole from ENVI many years ago. But
yes, this is easily set as the default stretch, if you
wanted it to be.)
>> There is nothing in the histogram part of XSTRETCH that
>> precludes using a 3D array. The only thing 2D about XSTRETCH
>> is that it assumes a 2D image array to display.
>
> So if I modify the code to display one slice of the 3D array it should
> work? The histogram would represent the 3D data?
Yes, certainly.
> We've communicated about my data before - you might remember the x-ray
> tomography data of air and water flow in soils I showed you when you
> were in Copenhagen. I didn't use my full name (Dorthe Wildenschild)
> when I signed up for the news group.
Sneaky, sneaky. But we *always* learn everything we
need to know about a person. :-)
> I've got data sets that are spread differently across the "color"
> (grey scale) spectrum, so I'm trying to find a threshold for one phase
> (the air) that will work for several volumes representing different
> saturations. Xstretch is such a nice tool for playing around with the
> cutoff, but I would like to take a more scientific approach than
> setting it to the value I think "looks" best.
Well, then you have to find some theoretical or physical
value that you can defend against the naysayers. But that's
science, not computer graphics. I make it a point to always
deal with the latter, if possible. :-)
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/
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