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Re: color table [message #8604 is a reply to message #8601]

Wed, 26 March 1997 00:00

J.D. Smith
Messages: 214
Registered: August 1996

Senior Member

Ye Hong wrote:
>
> Does anyone know why the system variable !d.table_size is changing ?
> Is !d.table_size machine-dependent?

!D.Table_Size represents the number of colors in IDL's internal color
table. It depends on your machine color bit depth (e.g. 8-bit or
24-bit).

> I have my own color table which includes 235 colors. When I need color
> image, I load it in. It has been working fine until yesterday when I
> found only first 90 color were loaded. It took me a while to figure out
> that !d.table_size was changed from 256 to 90. After I exited and
> re-ran IDL several time, I found !d.table_size was changing although it
> was 256 in most cases.

!D.Table_Size isn't set until you open an IDL window for the first
time. Until then, it defaults to 256 (which *doesn't* mean you have 256
colors). I open and delete a small window upon startup (via the idl
startup file) to ensure the system variable actually reflects the number
of available colors. Loadct does this for you when loading a built-in
color table. If you don't want to do this on startup, you could always
add code like:

if !d.name eq 'X' and !d.window eq -1 then begin ;Uninitialized?
;;If so, make a dummy window to determine the # of colors available.
window,/free,/pixmap,xs=4, ys=4
wdelete, !d.window
endif

The more colors being used by other applications (e.g. Netscape), the
fewer IDL can take for itself. Likely, when you only got 90, you were
running some other color hungry app.

To implement your color table, either create it on the fly to fit into
!D.Table_Size (which is fine if it's simple -- see
<http://www.dfanning.com/tips/create_colortable.html>), or store the
r,g,b vectors in a file, read them in, and down-sample by interpolation
to fit. This is essentially what loadct does with the built-in color
tables with a set of commands like:

if nc ne 256 then begin ;Interpolate
p = (lindgen(nc) * 255) / (nc-1)
r = r(p)
g = g(p)
b = b(p)
endif

where nc is the number of colors (defaults to !D.Table_Size) and the
r,g,b vectors are read in from colors1.tbl. You could be more careful
with your interpolation, if, for instance, you had a few colors that you
require to be in your map (e.g. some plotting colors at the bottom
end). You might then set these required colors (n of them,say), and
then interpolate the rest of your colormap onto the remaining
!D.Table_Size-n spots in the palette.

Good Luck,

JD

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[Message index]

		color table By: Ye Hong on Wed, 26 March 1997 00:00
		Re: color table By: J.D. Smith on Wed, 26 March 1997 00:00
		Re: Color table By: R.Bauer on Thu, 05 August 2004 06:41
		Re: Color table By: R.G. Stockwell on Thu, 05 August 2004 08:46
		Re: Color table By: David Fanning on Wed, 04 August 2004 21:05
		Re: Color table By: David Fanning on Mon, 21 January 2008 07:09
		Re: Color table By: WRC2008 on Thu, 24 January 2008 00:31
		Re: Color table By: WRC2008 on Mon, 21 January 2008 04:35
		Re: Color table By: WRC2008 on Mon, 21 January 2008 02:02
		Re: Color table By: David Fanning on Sun, 20 January 2008 09:53
		Re: Color table By: mmiller3 on Sun, 20 January 2008 07:58
		Re: Color table By: Vince Hradil on Sat, 19 January 2008 10:39
		Re: Color table By: WRC2008 on Sat, 19 January 2008 04:27
		Re: Color table By: David Fanning on Fri, 25 January 2008 05:23
		Re: Color table By: WRC2008 on Fri, 25 January 2008 04:47
		Re: Color table By: WRC2008 on Fri, 25 January 2008 02:35
		Re: Color table By: David Fanning on Fri, 25 January 2008 01:15
		Re: Color table By: WRC2008 on Fri, 25 January 2008 00:54
		Re: Color table By: David Fanning on Thu, 24 January 2008 10:00
		Re: Color table By: WRC2008 on Thu, 24 January 2008 09:41
		Re: Color table By: David Fanning on Thu, 24 January 2008 09:25
		Re: Color table By: WRC2008 on Thu, 24 January 2008 09:02
		Re: Color table By: David Fanning on Thu, 24 January 2008 08:19
		Re: Color table By: WRC2008 on Thu, 24 January 2008 07:17
		Re: Color table By: David Fanning on Thu, 24 January 2008 05:04
		Re: Color Table By: Nikola on Wed, 18 August 2010 05:44
		Re: Color Table By: panblosky on Tue, 17 August 2010 06:32
		Re: Color Table By: Wout De Nolf on Tue, 17 August 2010 05:42
		Re: Color table By: David Fanning on Sat, 10 November 2012 17:38

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