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Re: POLY_2D inconsitent interpolation [message #49789 is a reply to message #49704]

Fri, 11 August 2006 17:41

Randolf Klein
Messages: 6
Registered: August 2006

Junior Member

Wayne Landsman wrote:
> Examing the code for CONGRID one finds that use of the CENTER keyword
> alters the input parameters to POLY_2D by 0.5 for the interpolation
> cases but not for the nearest neighbor, just what was found was needed
> in the original posting by Craig DeForest.
>
> It sounds like a similar fix is needed to hastrom.pro in the IDL
> Astronomy Library but I don't have time to do this today (but probably
> within a week). --Wayne
>

Actually congrid uses INTERPOLATE. POLY_2D is only used in the nearest
neighbor sampling. I wonder, if this might also be the solution for hastrom.

But for now I am trying to work with the following change in hastrom.
Replace the call to polywarp with:
if interp eq 0 $ ;Get coefficients
then polywarp, x+.5, y+.5, xref, yref, degree, kx, ky $
else polywarp, x, y, xref, yref, degree, kx, ky

This is not ideal. The image does not get shifted around (good!), but
the area covered by the interpolation is shifted by half an original pixel.

RK

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[Message index]

		POLY_2D inconsitent interpolation By: Randolf Klein on Mon, 07 August 2006 16:31
		Re: POLY_2D inconsitent interpolation By: news.verizon.net on Fri, 11 August 2006 07:50
		Re: POLY_2D inconsitent interpolation By: Randolf Klein on Fri, 11 August 2006 17:41

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