[argyllcms] Re: argyllcms Digest V3 #172

  • From: Graeme Gill <graeme@xxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Tue, 02 Jan 2007 22:36:10 +1100

Martin Weberg wrote:

Any suggestions on how to find the true TAC?

It depends what you're after. The exact behaviour will depend
on the CMM used - different CMM's may use different interpolation
algorithms within a grid cell. Putting this aside, to narrow
down the worst case would probably involve searching the
cells for worst case candidates, and then using an
analytic or numerical approach to computing the worst
case within each cell. A cruder approach is to sample the
the profile behaviour, and hope that fine enough sampling
returns an accurate enough value.

(you didn't do a new profile with the FOGRA39L-data with your development
code then running icclu?)

Yes, the results are a little different. Possibly this is due to
not using CIE delta E 94 in computing the per channel curves in
the V0.60 release.

The differences in the underlying profile (as opposed to the B2A table)
are smaller:

xicclu -fif -ir FOGRA39L_v60.5.icm
0.000000 0.000000 0.000000 [Lab] -> Lut -> 1.000000 0.857005 0.475548 1.000000 
[CMYK] (clip)

xicclu -fif -ir FOGRA39L_vcurr.icm
0.000000 0.000000 0.000000 [Lab] -> Lut -> 1.000000 0.856197 0.457543 1.000000 
[CMYK] (clip)

Graeme Gill.

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