[argyllcms] Re: Devicelink Black Generation
- From: Graeme Gill <graeme@xxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Tue, 12 Aug 2008 16:54:28 +1000
Fabrizio Levati wrote:
I am trying to create a devicelink profile to convert from ISOwebcoated to
ISOnewspaper (but could be any other kind of repurposing from one printing
press/process to another) and I am not able to tweak the black generation
without loosing the purity of the primaries.
It seems to me you are at cross purposes here. The whole point about
repurposing is to maintain the color, which if the two devices have
different colorants, means using different primary combination values
to represent corresponding colors, thereby resulting in non pure primaries.
Besides the CMY purity, what I am trying to achieve is to create a
devicelink with my own GCR and preserve the pure (100%) BLACK in the text.
Once again you seem to be at cross purposes. You can't impose a GCR and
also translate the incoming black ratio through to the output, since
these aims contradict each other.
Considering that even the kt option result in a ³contaminated² black text,
I am now wondering if and how this is possible.
The reason that K only in doesn't produce K only out with -kt
for the type of profiles you are using, is that color
accuracy is given a higher priority than black inking,
and the source profile has a lot blacker K only black
than the destination, so CMY is added to reduce
the error.
Note that collink has a -f option, that forces neutral input colors
to be K only output, but this probably doesn't do what you want,
since it will force CMY0 to K only too.
It's not too hard for me to add another option to collink
to force K only output for K only input. If I do this:
collink -v -qm -kt -ims -fk offset.icm newspaper.icm test.icm
I get this sort of result:
icclu test.icm
0.000000 0.000000 0.000000 0.000000 [CMYK] -> Lut -> 0.000000 0.000000 0.000000
0.008345 [CMYK]
1.000000 0.000000 0.000000 0.000000 [CMYK] -> Lut -> 1.000000 0.000000 0.000000
0.015225 [CMYK]
0.000000 1.000000 0.000000 0.000000 [CMYK] -> Lut -> 0.000000 1.000000 0.003097
0.000000 [CMYK]
0.000000 0.000000 1.000000 0.000000 [CMYK] -> Lut -> 0.000000 0.000000 1.000000
0.002731 [CMYK]
0.000000 0.000000 0.000000 1.000000 [CMYK] -> Lut -> 0.043310 0.053822 0.000000
1.000000 [CMYK]
1.000000 1.000000 1.000000 0.000000 [CMYK] -> Lut -> 0.674325 1.000000 0.000000
0.767079 [CMYK]
I'll include this new option in the V1.0.2 release.
Graeme Gill.
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