| Re: interpolation for resizing [message #64211 is a reply to message #64148] |
Fri, 05 December 2008 00:36  |
loebasboy
Messages: 26
Registered: August 2008
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Junior Member |
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On 3 dec, 16:49, bryan.s.h...@gmail.com wrote:
> On 12월3일, 오전7시52분, loebasboy <stijn....@gmail.com> wrote:
>
>
>
>
>
>> On 3 dec, 14:43, David Fanning <n...@dfanning.com> wrote:
>
>>> Craig Markwardt writes:
>>>> That's true, but nearest-neighbor sampling also adds high-frequency
>>>> aliases, so what one uses to interpolate does depend on what one
>>>> needs.
>
>>> I have a feeling it will be some weeks before the person
>>> asking the question feels compelled to ask about this
>>> complication. ;-)
>
>>> Cheers,
>
>>> David
>
>>> P.S. Isn't a 100 by 100 image, uh, pretty small to be
>>> doing *any* high-resolution analysis? Certainly too
>>> small to be worried about high-frequency aliasing.
>>> You should be thinking about other problems, my friend!
>
>>> --
>>> David Fanning, Ph.D.
>>> Fanning Software Consulting, Inc.
>>> Coyote's Guide to IDL Programming:http://www.dfanning.com/
>>> Sepore ma de ni thui. ("Perhaps thou speakest truth.")
>
>> About interpolate and other related functions... is it possible to use
>> these function to interpolate data where there is no data in a grid.
>> For instance I have the following code:
>
>> a= findgen(5,5)
>> a[3,3] = -999
>> a[1,2] = -999
>> indices = where(a EQ -999)
>> b = interpolate(a, indices)
>
>> and the interpolated numbers in b are interpolated with available
>> numbers in 2 dimensions...
>
>> Is there a function in IDL that can do this, because interpolate and
>> other related functions work differently I guess (making extra rows or
>> columns between rows or columns). I'm sorry that this is a very 'open'
>> question but I'm rather busy and this something I could use later on.- 따온 텍스트 숨기기 -
>
>> - 따온 텍스트 보기 -
>
> Replacing the fill value to a string, for example 'NaN', will exclude
> the pixels when using 'congrid' or 'rebin'.- Tekst uit oorspronkelijk bericht niet weergeven -
>
> - Tekst uit oorspronkelijk bericht weergeven -
I guess you didn't read my question properly (although I maybe didn't
have to ask it in this thread to avoid this, but I didn't want to make
a new thread because of David's post several days ago). I'm not trying
to resize anything. I just want the -999 or NaN (I make them with !
Values.F_NAN option btw.) values to have a value in the b array that
is calculated by interpolation (for instance: the IDW of the
surroundig pixels in a 3x3 window).
So sorry for the mixup and thanks if you guys still feel like finding
a solution for this.
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