| Re: Fractional Pixels Origin? [message #47628 is a reply to message #47583] |
Fri, 17 February 2006 14:28   |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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JD Smith writes:
> Sorry, I had it backwards, FITS centers the first pixel at [1,1], and
> the Nasa library uses [0,0] (which is called "IDL convention"). If
> you have a choice, don't choose the FITS standard ([1,1]), or the "IDL
> convention" ([0,0]), but the natural "I'm a tiny ant living on the
> surface of your detector and measuring pixel positions from the edge
> with my tiny little ruler": [0.5,0.5]. The only disadvantage is all
> pixel centers are now fractional.
>
> Wayne is very careful to document the convention in all of the NasaLib
> routines, so if confused be sure to read the useful doc headers (as I
> just did to remedy my confusion!).
Do you think there is such a thing as knowing too much about
a subject? Two days ago as was as happy as a clam. Now I'm
paranoid as hell. :-(
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/
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