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[argyllcms] Re: False colors with shaper/matrix display profiles

From: Graeme Gill <graeme@xxxxxxxxxxxxx>
To: argyllcms@xxxxxxxxxxxxx
Date: Thu, 31 Aug 2006 01:16:36 +1000

When i generate shaper/matrix profiles, however, and then
use these profiles (with Scribus, or with tifficc to manually
correct images for the displays), i get bright
false colors in some very dark image areas. Using
-qh with 'profile' reduces these areas, but the problem
itself persists.


Does this occur if you use (Argyll's) cctiff ?

Without the profiles you are using, I'm only guessing,
but it sounds rather like a bug in cctiff that I fixed
in V0.52, that was triggered when a profile created device
values values > 1.0 for certain PCS inputs, causing pixel
value wraparound. The profile triggering it is probably
actually the other profile you are using, a gamma/shaper
profile, since the gamma curve doesn't naturally
clip the device values the way the shaper curve
lookup does.
I'd need to look at both profiles to be sure though.

If in fact it is the same type of thing, then
changing Argyll profile won't fix this, since it's the other
profile that triggers the problem, and in fact it's
a problem not with the profile, but with the pixel
conversion engine Scribus and tifficc are using (lcms ?).

Graeme Gill.

Follow-Ups:

[argyllcms] Re: False colors with shaper/matrix display profiles
From: Oliver Schulz

References:
- [argyllcms] False colors with shaper/matrix display profiles
  - From: Oliver Schulz

[argyllcms] Re: False colors with shaper/matrix display profiles

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