ps.map 24 bits

[Conn Copas]

iamson??at?May?17??95?10?24?31?am at bnr.ca>
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Malcolm Williamson writes in response:
> 
> I guess my response is, no, I'm not positive. Images created using ps.map 
> and printed on a 24-bit dye-sublimation printer are _definitedly_ more 
> than 8-bit, but they could be something less than 24-bit. They _look_ 
> like "true-color" to me, though. Are you sure that ghostscript is capable 
> of displaying 24-bit, regardless of whether the PostScript image is?
> 
> I suppose I could look in the trusty PostScript reference manual to 
> finish this debate... :-)
> 
In my case, a little knowledge could be a dangerous thing here, but here goes
anyway. When ghostscript displays anything, it calls the 'x11' driver. One of
the first things that driver must do is make an Xlib call to open a graphics
window, in the same way that the Grass Xdriver does. On both Suns and SGI's,
the default window is 8 bit pseudo colour, unless otherwise instructed. Now
for the big questions: (a) does ghostscript have the capability of determining
whether the data is 24 bit, and (b) does it bother to check the capabilities
of the display system? 

-- 
Conn V Copas
Information Technology Division
Defence Science and Technology Organisation
PO Box 1500
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Australia       e-mail: cvc at itd.dsto.gov.au
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