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Re: Omit a color

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In article <0278a83e-9e2e-4497-bbdd-9dcb438286c2@googlegroups.com>, 
news@ademmler.com says...
> 
> Dear Ken,
> 
> thx for your very detailed explanation. This explains a lot.
> You are right about the color names - has been a typo from copy paste. 
> I was playing with ghostscript using this command.
> 
> gs -sDEVICE=tiffsep -dNOPAUSE -dBATCH -sOutputFile=test.tiff -r50 -csetcolor.ps -f test.pdf
> 
> While setcolor.ps contains:
> <<
> /Separations true
> /Setoverprint true
> /ProcessColorModel /DeviceCMYK
> /SeparationColorNames [ /Black /Spot ] /SeparationOrder [ /Black /Spot ]
> >> setpagedevice
> 
> I still get all colors as separations C +M + Y + K + Spot
> 
> Any idea what I am doing wrong here?

Nothing.

There isn't anything in the PostScript Language which says you can force 
the device not to produce the Process Color Model colourants.

If you look at page 437 onwards in the PLRM it basically says that the 
ProcessColorModel colourants are always available and the 
SeparationColorNames parameter declares the names of *additional* spot 
colourants.

So in your case the ProcessColorModel is DeviceCMYK and you have defined 
an additional colourant of /Spot. The result is that you get CMYK+Spot 
plates.

The *only* device colour model which does not imply a ProcessColorModel 
is DeviceN.

Ghostscript does have a devicen device and that will, broadly, behave in 
the manner you want I think. But its really intended as a 
demonstration/test harness, not for actual production. The output format 
of the colourants is 'bit' which is probably not useful. Also my 
experimentation with this device doesn't seem to produce anything useful 
with DeviceN. Its not my specialist subject so I could be doign 
something wrong.

However, I don't really see the problem, if you're using Ghostscript to 
produce plates, just ignore the ones you don't want. If you're using 
Ghostscript just to test out PostScript you intend to send to another 
RIP then I'm afraid you are out of luck, you're in device-dependent 
behaviour here, and what Ghostscript chooses to do won't reflect what 
another device might choose to do.

Perhaps it would help if you could explain *why* you want to only 
produce certain plates.


			Ken

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Thread

Omit a color MrDemmler <news@ademmler.com> - 2019-11-26 13:14 -0800
  Re: Omit a color MrDemmler <news@ademmler.com> - 2019-11-26 13:28 -0800
    Re: Omit a color ken <ken@spamcop.net> - 2019-11-27 08:31 +0000
      Re: Omit a color MrDemmler <news@ademmler.com> - 2019-11-27 09:25 -0800
        Re: Omit a color ken <ken@spamcop.net> - 2019-11-28 09:58 +0000
  Re: Omit a color ken <ken@spamcop.net> - 2019-11-27 08:26 +0000

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