comp.lang.idl-pvwave archive: archive » Re: Array indices and lookup tables

Home » Public Forums » archive » Re: Array indices and lookup tables

Show: Today's Messages :: Show Polls :: Message Navigator
E-mail to friend

Re: Array indices and lookup tables [message #39754 is a reply to message #39753]

Wed, 09 June 2004 07:06

Haje Korth
Messages: 651
Registered: May 1997

Senior Member

David,
damn, I was sure you had your coffee already by now. But then again, I am
two hours ahead of you. :-) To answer your question: Yes, I am *sure* I need
the lookup table. What I am doing is to transform a geographic map to
geomagnetic coordinates. Now, this would not be so bad if it only had to be
done once. But the map is composed out of two maps forming a day and a
nightside. The composition thus depends upon time of day as well as on
season. It is impossible to create images for all possible times and thus
they need to be created on the fly. As you can imagine I try to avoid having
to drink a whole pot of coffee until the conversion is completed. :-)

Since the conversion between geomagnetic and geographic coordinates is
nearly fixed a lookup table will do the job nicely. Is there a one line
command that will do the job using the right number of [ and ] in the right
order? Well, anything will do that prevents me from loopong through 1
million+ elements.

Cheers,
Haje

"David Fanning" <davidf@dfanning.com> wrote in message
news:MPG.1b30c1a7910a91fa989789@news.frii.com...
> Haje Korth writes:
>
>> I am working on a coordinate transformation for a map and I have a
simple
>> problem. My mind is alreay blocked early in the morning and I could use
some
>> input: I have an rgb image of dimensions [3,1440, 720]. I need to
rearranged
>> the pixel in the image according to a lookup table of dimension
>> [2,1440,360], which contains the column and row of the new pixel
assigned to
>> a location. Is there a magic way to do this without looping through each
>> pixel in IDL?
>
> Oh, dear. Come back after I've had a couple of cups
> of coffee, would you. :-(
>
> Cheers,
>
> David
>
> P.S. With the (what!?) thousand different map projections
> now in IDL, are you *sure* you need a look-up table? :-)
>
> --
> David Fanning, Ph.D.
> Fanning Software Consulting, Inc.
> Coyote's Guide to IDL Programming: http://www.dfanning.com/

Report message to a moderator

[Message index]

		Re: Array indices and lookup tables By: David Fanning on Thu, 10 June 2004 06:59
		Re: Array indices and lookup tables By: David Fanning on Thu, 10 June 2004 06:57
		Re: Array indices and lookup tables By: Haje Korth on Thu, 10 June 2004 06:11
		Re: Array indices and lookup tables By: Chris Lee on Thu, 10 June 2004 01:39
		Re: Array indices and lookup tables By: Haje Korth on Wed, 09 June 2004 07:49
		Re: Array indices and lookup tables By: David Fanning on Wed, 09 June 2004 07:26
		Re: Array indices and lookup tables By: Haje Korth on Wed, 09 June 2004 07:06
		Re: Array indices and lookup tables By: David Fanning on Wed, 09 June 2004 06:42
		Re: Array indices and lookup tables By: Chris Lee on Thu, 10 June 2004 10:15

Previous Topic:	Object Graphics Fonts
Next Topic:	IsoSurface Contour projection

-=] Back to Top [=-

[ Syndicate this forum (XML) ] [

] [

]

Current Time: Tue Dec 02 11:37:21 PST 2025

Total time taken to generate the page: 0.87570 seconds