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Re: rebin question [message #29822 is a reply to message #11091]

Fri, 22 March 2002 09:11

hradilv.nospam
Messages: 19
Registered: November 2001

Junior Member

print, round(rebin(float([5,5,5,5,4]),1))

Hassle?

Maybe you could write a function. Which leads me to a new question:

Is it possible to define a function or procedure in IDL that can take
an arbitrary number of arguments, e.g.:

function my_rebin, a, arg1, arg2, ...

return, round( rebin( float(a), arg1, arg2, ... ) )
end

On Fri, 22 Mar 2002 11:58:41 -0500, Jonathan Joseph <jj21@cornell.edu>
wrote:

> I figured I would use rebin to downsample an image by averaging the
> pixels in blocks of specified size. What I discovered, was that for
> integer type images, rebin averages the pixels, but then instead of
> rounding to the nearest integer, simply takes the integer part of
> the average. Hence:
>
> print, rebin([5,5,5,5,4], 1)
>
> gives the result of 4, not 5 which is what I would like. I suppose
> this is done for speed - to work around the problem, I need to convert
> to a floating point type, do the rebin, then round, then convert back
> to the proper integer type - a hassle.
>
> But, I would really like a more generic way of doing downsampling
> of this sort, without the high overhead of a loop. Apart from
> taking the mean of a block of pixels, I would also like the option
> of downsampling using the median of a block of pixels, or using the
> mean of a block of pixels disregarding the farthest outlier (or
> n outliers).
>
> Has anyone written IDL code to do downsampling in a more generalized
> way than rebin, or have any clever ideas about how to do it quickly?
>
> Thanks

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[Message index]

		REBIN Question By: pford on Sat, 14 March 1998 00:00
		Re: REBIN Question By: pford on Wed, 18 March 1998 00:00
		Re: REBIN Question By: Armand J. L. Jongen on Tue, 17 March 1998 00:00
		Re: rebin question By: hradilv.nospam on Fri, 22 March 2002 09:11
		Re: rebin question By: Mark Fardal on Sun, 24 March 2002 22:50
		Re: rebin question By: Jonathan Joseph on Fri, 22 March 2002 10:40
		Re: rebin question By: Craig Markwardt on Fri, 22 March 2002 10:31
		Re: rebin question By: Jonathan Joseph on Mon, 25 March 2002 14:24
		Re: rebin question By: Mark Hadfield on Mon, 25 March 2002 14:07
		Re: rebin question By: JD Smith on Fri, 22 March 2002 11:49
		Re: rebin question By: Jonathan Joseph on Fri, 22 March 2002 11:20
		Re: rebin question By: David Fanning on Fri, 22 March 2002 11:14
		Re: rebin question By: hradilv.nospam on Fri, 22 March 2002 10:53
		Re: rebin question By: Jonathan Joseph on Fri, 22 March 2002 10:53

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