[argyllcms] Re: xicclu -g predictability issue

  • From: Graeme Gill <graeme@xxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Mon, 31 Jan 2011 13:37:38 +1100

Gerhard Fuernkranz wrote:
Using a profile created from Elena's ofps2.ti3 data I did take a closer
look at a short line crossing one of the discontinuities (a straight
line in the source sRGB space, which is then converted with perceptual
intent to CMYK).

And it seems to happen at a location where CMYK colorants are crossing
very steeply. Note that the 101 CMYK points below spawn only a couple of
dE in total!

Right. So it seems that this is not a bug in the inversion
algorithm, but reflects the sudden shift in K vs. CMY at
that particular spot on the gamut boundary.

So possibly limiting the 1st derivatives may be a key to success?

The problem is that gamut has a priority that trumps any secondary
factor. A more complicated approach is needed to set a trade-off
between gamut volume and device value smoothness.

Graeme Gill.

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