[argyllcms] Re: FWA content found in 'spec2cie', but not in 'profile'

  • From: Graeme Gill <graeme@xxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Wed, 10 Jan 2007 00:03:34 +1100

Thomas Baumann wrote:
There is something about FWA content detection I do not understand. In my
case there is FWA recognized in 'spec2cie' but not in 'profile':

$ profile -f -i D50 test
~1 FWA content = 0.000000

$ spec2cie -f test.ti3 test_2.ti3
Found media white: 0.864557 0.888193 0.766133
~1 FWA content = 0.736019

Hello Thomas,

One of the pieces of information the FWA code needs to
do its job, is the spectrum of media, to estimate the FWA content.

It turns out that spec2cie and profile use a different algorithm
to pick the media patches. spec2cie picks the single patch
with the highest Y value. profile tries to identify all the
media patches by looking at the device values, and then averages
them all.

I only ever used FWA compensation with CMYK devices, and I've
overlooked the fact that it's hard coded to look for CMYK == 0
patches. Feed it an RGB file, and it picks all the black patches :-(

Thanks for drawing this bug to my attention. I'll fix it in the
next release. The workaround as you might guess, is to use
spec2cie in front of profile.

Graeme Gill.

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