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Re: Building Voxel arrays from png files (compression, analysis, and visualization) [message #45202]

Mon, 22 August 2005 16:43

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

Greener writes:

> Thank you for your reply. Just before I viewed this page I printed off
> the page that you linked me to. Hopefully that is a good sign :-)
> I will try both the rebin and congrid functions, I am pretty sure that
> they both use interpolation to calculate the new voxel values. I have
> been trying to figure out how the interpolation within IDL actually
> works (in hopes to reduce the data loss I notice during compression,
> oh, and I am no mathematician either, can anyone say 'fish out of
> water' :-) I have looked for the interpolate function script with no
> success as of yet.

The INTERPOLATE command is an internal command, so you won't find
a script for it. Loss of information is inevitable, of course, if
you change the size of the array. You should try resizing with both
nearest neighbor and bilinear sampling. (Check the keywords to REBIN
and CONGRID.) In our medical images, we usually use bilinear sampling.
It is good enough for our purposes, but you might need something better.
I've heard wavelets are good for this, but I've never used them.

> Thanks again for your advice, I have noticed a fairly significant
> improvement just with the removal of the [*,*,*].

Well, we are headed in the right direction then. That's a good
thing. :-)

Cheers,

David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/

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		Re: Building Voxel arrays from png files (compression, analysis, and visualization) By: David Fanning on Mon, 22 August 2005 16:43
		Re: Building Voxel arrays from png files (compression, analysis, and visualization) By: Greener on Mon, 22 August 2005 14:22
		Re: Building Voxel arrays from png files (compression, analysis, and visualization) By: David Fanning on Mon, 22 August 2005 12:48

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