[argyllcms] Re: xicclu -g predictability issue

  • From: Gerhard Fuernkranz <nospam456@xxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Mon, 31 Jan 2011 00:19:08 +0100

Am 30.01.2011 20:03, schrieb Elena [service address]:
> One was for example the option -kl of xicclu which I never noticed. Another 
> is the difference between Locus and Value in argyll jargon, I maybe stupid 
> but I didn't understand it yet.

My understanding is that "value" refers to an actual amount of K, while
"k locus" refers to a relative amount of K (where locus =1.0 refers to
the K value that would be selected by -kx, while 0.0 refers to the K
value that would be selected by -kz).

>> I however just discovered another gap of mine, till now I misunderstood that 
>> -kz actually generated NO K at all.

"-kz" attempts to reproduce a given L*a*b* color exactly, using as
little K as possible. If it happens that the given color can be
reproduced without K, then consequently no K will be used at all. For
colors which cannot be reproduced without adding some black ink
(typically rather darker colors, near the gamut boundary), -kz does well
generate non-zero K.

> My strong suspect is that argyll fails not just because it has no checks 
> against discontinuities, but mostly because the .ti3 is noisy, and/or not 
> precise or dense enough in some dark areas.

I don't know yet whether this is really just noise or anything else. One
would likely need to investigate all the involved cells of the A2B grid
in detail - but that's quite tedious...


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