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Re: Image warping in IDL [message #51277 is a reply to message #51188]

Thu, 09 November 2006 11:50

JD Smith
Messages: 850
Registered: December 1999

Senior Member

On Thu, 09 Nov 2006 13:37:21 +0100, Wox wrote:

> On 8 Nov 2006 21:49:19 -0800, "Robbie" <retsil@iinet.net.au> wrote:
>
>> I don't really understand the problem fully, but I'm sure that
>> INTERPOLATE does all the hard work for you.
>
> That would be for reverse mapping. In forward mapping, it's the
> resampling (the for-loops in the original post) that takes processing
> time. There isn't really a memory problem here.
>
> So the problem in short:
> 1. How to get ride of the looping in the resampling step
> OR
> 2. How to prevent having to do the resampling in the first place
> (going to reverse mapping by having a "magical operation" converting
> the 2D spline coefficients)

I'm afraid if you want to get any further with this, you are going to
have to illustrate the issue with a small amount of actual IDL code.
What do you actually have in hand? The output of TRIANGULATE without
the anchor points themselves? Just the map of fractional pixel
positions in the input image for each pixel in the output image (as
obtained by, e.g. TRIGRID)? If it's the latter, there must have been
some higher-level method for defining the warp. Rather than start
with the pixel-by-pixel mapping, I'd suggest going upstream. If you
can't go upstream, you'll have to triangulate your entire forward map,
and then sample it at the fixed x,y grid positions of the input array.
This may not give a unique solution, depending on how perverse the
mapping is (it could fold onto itself, for instance).

JD

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[Message index]

		Image warping in IDL By: Wox on Wed, 08 November 2006 04:53
		Re: Image warping in IDL By: David Fanning on Fri, 10 November 2006 15:11
		Re: Image warping in IDL By: JD Smith on Fri, 10 November 2006 14:51
		Re: Image warping in IDL By: Wox on Tue, 14 November 2006 02:20
		Re: Image warping in IDL By: JD Smith on Mon, 20 November 2006 12:17
		Re: Image warping in IDL By: James Kuyper on Fri, 10 November 2006 08:38
		Re: Image warping in IDL By: Wox on Fri, 10 November 2006 01:12
		Re: Image warping in IDL By: Wox on Fri, 10 November 2006 01:05
		Re: Image warping in IDL By: JD Smith on Thu, 09 November 2006 11:50
		Re: Image warping in IDL By: Wox on Wed, 15 November 2006 04:18
		Re: Image warping in IDL By: Wox on Tue, 14 November 2006 08:20
		Re: Image warping in IDL By: Wox on Tue, 21 November 2006 01:18
		Re: Image warping in IDL By: JD Smith on Tue, 21 November 2006 09:10
		Re: Image warping in IDL By: Jeff Hester on Mon, 20 November 2006 09:00
		Re: Image warping in IDL By: Wox on Mon, 20 November 2006 01:18
		Re: Image warping in IDL By: JD Smith on Wed, 22 November 2006 08:22
		Re: Image warping in IDL By: Wox on Wed, 22 November 2006 00:21

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