| Re: log scale colorbar in IDL 8.0 [message #76094 is a reply to message #76091] |
Wed, 18 May 2011 11:27   |
pgrigis
Messages: 436
Registered: September 2007
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Senior Member |
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On May 18, 1:26 pm, David Fanning <n...@idlcoyote.com> wrote:
> Paolo writes:
>> Yes, we had. Well I wasn't thinking in term
>> of color bars anymore but general images.
>> For instance, a logarithmic y-axis is used often
>> to produce spectrograms - see for instance:
>
>> http://swaves.gsfc.nasa.gov/content_images/swavesf1.png
>
>> note the logarithmic y-scaling
>
> Don't you have something like this already, Paolo?
> I thought you built this. If you want to turn it
> into a Coyote Graphic routine, it's pretty simple.
> I'll sell you a book that explains it in detail. ;-)
Yes I do,
but I was worried that in the CG era people may shun
older-fashioned programs that do not have those fancy
features like automatic resizing etc.
The trick is to choose a good interpolation scheme
for the pixel values - the one I have in my
http://hea-www.cfa.harvard.edu/~pgrigis/idl_stuff/pg_plotima ge.pro
may not be suitable for all uses though.
Ciao,
Paolo
>
> Actually, it's so simple you probably won't need
> a book. Probably it is only a matter of using
> Coyote Graphics routines internally, and it will
> probably just work! (Maybe with some color modifications
> so it can work in both decomposed and indexed color.)
>
> But, if you just want log scaling on the axes, that's
> already built into cgImage:
>
> IDL> image = scale_vector(cgdemodata(7), 1, 1000)
> IDL> cgimage, image, /axes, /scale, $
> axkeywords={ylog:1, yrange:[1,1000]}
>
> Cheers,
>
> David
>
> --
> David Fanning, Ph.D.
> Fanning Software Consulting, Inc.
> Coyote's Guide to IDL Programming:http://www.idlcoyote.com/
> Sepore ma de ni thui. ("Perhaps thou speakest truth.")
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