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Re: can't change colortable in current window (linux bpp24) [message #16285 is a reply to message #16278]

Fri, 16 July 1999 00:00

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

Senior Member

Liam Gumley wrote:
>
> Olivier ARCHER wrote:
>> when i load a color table with loadct *after* opening a window, nothing
>> happen. here a piece of code producing the error:
>>
>> device,decompose=0
>> window,/free && tv,dist(400) ;; picture in B/W
>> loadct,4 ;; this have no effect in the current
>> window ( no error messages )
>> window,/free && tv,dist(400) ;; picture in color; loadct effect...
>>
>> this fail on a linux rh6 , with dpyinfo saying that my X serveur is
>> TrueColor, with 24 plane depth
>> this work on solaris( creator 3D graphics card) , with dpyinfo saying
>> that my X serveur support various combination of class/depth.
>
> Olivier,
>
> The behavior you describe is actually a *feature* of 24-bit TrueColor
> mode in IDL. You can certainly do a lot of neat stuff in 24-bit mode, as
> described David's excellent articles. A quick way around this problem in
> 24-bit mode is to always load the color table just before displaying the
> image, e.g.
>
> loadct, 4
> tvscl, dist(256)
>
> However if you really *want* all of your graphics displays to update
> automatically any time you change the color table (using LOADCT,
> XLOADCT, or TVLCT), *and* you don't mind the limitations of 8-bit
> PseudoColor mode in IDL, then type the following commands just after
> starting a new IDL session:
>
> device, pseudo=8, decomposed=0, retain=2 ; select PseudoColor mode
> window, /free, /pixmap ; lock this mode by opening a window
> wdelete, !d.window
>

Sadly, the most popular X servers for Linux (XFree86) do not support
overlays... I.E. they can't do PseudoColor when running in TrueColor
mode. Version 4.0 will add this feature, but it is far from ready.

JD

--
J.D. Smith |*| WORK: (607) 255-5842
Cornell University Dept. of Astronomy |*| (607) 255-6263
304 Space Sciences Bldg. |*| FAX: (607) 255-5875
Ithaca, NY 14853 |*|

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[Message index]

		Re: can't change colortable in current window (linux bpp24) By: J.D. Smith on Fri, 16 July 1999 00:00
		Re: can't change colortable in current window (linux bpp24) By: David R. Klassen on Fri, 16 July 1999 00:00
		Re: can't change colortable in current window (linux bpp24) By: Liam Gumley on Fri, 16 July 1999 00:00
		Re: can't change colortable in current window (linux bpp24) By: J.D. Smith on Fri, 16 July 1999 00:00
		Re: can't change colortable in current window (linux bpp24) By: Liam Gumley on Fri, 16 July 1999 00:00
		Re: can't change colortable in current window (linux bpp24) By: davidf on Fri, 16 July 1999 00:00

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