[argyllcms] Re: Detecting if a point is in or out of gamut

  • From: Graeme Gill <graeme@xxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Tue, 21 Aug 2007 11:32:36 +1000

John Weissberg wrote:

With function xicclu and an ICC profile that contained an LUT, I would like to know more about the differences between options:

-fif and -fb

-fb uses the B2A table to do a PCS to device lookup.

-fif inverts the A2B table to do a PCS to device lookup. Since
an ICC profile is basically defined by the colorimetric A2B table
(the original instrument measurements having been discarded,
or stored merely as annotation), then inverting the A2B is likely
to be the closes you can get practice to determining what is in-gamut.

I believe that lcms uses a round trip between the colorimetric
A2B and B2A tables to detect out of gamut colors. This is likely
to be more accurate than the gamut table, but not perfectly accurate,
since it relies on the B2A table which is only going to approximate
the inverse of the A2B table.

Graeme Gill.

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