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Re: 24 bit colors in IDL [message #13671 is a reply to message #13280]

Thu, 19 November 1998 00:00

Vapuser
Messages: 63
Registered: November 1998

Member

davidf@dfanning.com (David Fanning) writes:

Dave;

I don't think this will work. On my SGI running Irix 6.5 and idl
5.1.1 just making the 'Device, Get_Visual_Name=thisName' call set's
the visual class. I issued the following statements as the first
statements after starting IDL.

IDL> device,get_visual_name=name & print,name
DirectColor
IDL> device,pseudo=8
^^^^^^^^^^^^^^^

IDL> device,get_visual_name=name & print,name
DirectColor
^^^^^^^^^^^

IDL> window
IDL> print,!d.n_colors
16777216

IDL>exit
Process idl finished

Similarly ...

IDL> device,pseudo=8
IDL> device,get_visual_name=name & print,name
PseudoColor
IDL> device,true=24
IDL> device,get_visual_name=name & print,name
PseudoColor
IDL> window
IDL> print,!d.n_colors
41
IDL> exit
Process idl finished

The help file says...

The colormap/visual class combination is chosen when IDL first
connects with the X Window server. Note that if you connect with the X
server by creating a window or

using the DEVICE keyword to the HELP procedure,
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

the visual class will be set; it then cannot be changed
until IDL is restarted. If you wish to use a visual class other than
the default, be sure to set it with a call to the DEVICE procedure
before creating windows or otherwise connecting with the X Window
server.

I suspect that the same mechanism is used by
'device,get_visual_name=name' as is used in help,/device. In order to
answer the question, a connection is made to the X-server, the die is
cast, the matter is settled.

If a connection to the X-server has not been made, I would rather see
a "don't know" message returned,rather than have IDL decide on the
visual. At least that way, when some routine started up, I'd know that
I still have the option of pseudo color or true color available. This
way, just asking the question decides the answer.

>
> Andy Bristow (ajbristow@dera.gov.uk) writes:
>
>> I was just getting my head round 24-bit, having been prompted by this
>> thread. So, at Philip's suggestion I went to
>>
>> http://www.dfanning.com/tips/colors24.html
>>
>> All well and good. Sounds relatively straightforward.
>>
>> So on my SGI (IRIX 6.5.1, IDL 5.1) I tried some of the
>> suggested code (immediatley after starting IDL up):
>>
>> device,decomposed=0
>> tvlct,[[255],[255],[0]],100
>> plot,randomu(10,10),color=100
>>
>> expecting the plot to be yellow, as advertised. Except no, _I_
>> get a medium-light shade of grey!
>>
>> Any suggestions?
>
> Oh, dear. I think this is one of those TrueColor/DirectColor
> tricks that SGI engineers like to play on people. This is
> a complication that I don't *even* want to know about.
>
> Try this. Type this:
>
> Device, Get_Visual_Name=thisName
> Print, thisName
>
> If thisName is "TrueColor" change it to "DirectColor":
>
> Device, DirectColor=24
>
> If thisName is "DirectColor" change it to "TrueColor":
>
> Device, TrueColor=24
>
> Do this *before* you open any graphics windows in IDL.
> Try the code above again. Different? The same?
>
> Please let us know. :-(
>
> Cheers,
>
> David
>
> Note: A copy of this article was e-mailed to the original poster.
>

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[Message index]

		24 bit colors in IDL By: Richard Penrose on Tue, 03 November 1998 00:00
		Re: 24 bit colors in IDL By: davidf7203 on Fri, 06 November 1998 00:00
		Re: 24 bit colors in IDL By: philip aldis on Fri, 06 November 1998 00:00
		Re: 24 bit colors in IDL By: davidf on Thu, 12 November 1998 00:00
		Re: 24 bit colors in IDL By: Richard Penrose on Wed, 11 November 1998 00:00
		Re: 24 bit colors in IDL By: Andy Bristow on Tue, 17 November 1998 00:00
		Re: 24 bit colors in IDL By: Nigel Wade on Thu, 19 November 1998 00:00
		Re: 24 bit colors in IDL By: davidf on Wed, 18 November 1998 00:00
		Re: 24 bit colors in IDL By: Nigel Wade on Wed, 18 November 1998 00:00
		Re: 24 bit colors in IDL By: Andy Bristow on Wed, 18 November 1998 00:00
		Re: 24 bit colors in IDL By: davidf on Tue, 17 November 1998 00:00
		Re: 24 bit colors in IDL By: davidf on Fri, 20 November 1998 00:00
		Re: 24 bit colors in IDL By: Vapuser on Fri, 20 November 1998 00:00
		Re: 24 bit colors in IDL By: davidf on Thu, 19 November 1998 00:00
		Re: 24 bit colors in IDL By: Vapuser on Thu, 19 November 1998 00:00

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