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Re: IDLanROI Confusion

Craig Markwardt (craigmnet@cow.physics.wisc.edu) writes:

> More than likely the region of interest becomes pixelated into square
> pixels.  It's pretty clear to me that this will give a greater
> perimeter than a true circle since there are more horizontal and
> vertical segments than are required.

It is true that this perimeter measurement is affected
by pixelation. I've found that by first smoothing the
data before I calculate the ISOCONTOUR, then using
those values for the IDLanROI object, I can get
within a couple of percent of the actual value, as
opposed to the normal 15-17%.

By the way, I just noticed that the connectivity
and vertices values on the ISOCONTOUR command are
actually reversed from what is printed in the on-line
help. That may explain a bit of my confusion. :-)



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/
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