[argyllcms] Re: Device link gamut mapping: how to do it right?
- From: Graeme Gill <graeme@xxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Mon, 08 Sep 2008 17:03:49 +1000
Nikolay Pokhilchenko wrote:
I have doing linking with perceptual intent after "tiffgamut -ia -pj". I've
noticed
that the result of that linking is white point mismatch between source and
destination
gamuts, which seen in checking *.wrl.
Yes, because that is effectively what you asked for : - an absolute
space in appearance coordinates using the colorimetric table. It's probably not
documented very well, but to support absolute reproduction while using
appearance space, argyll supports the concept of an absolute appearance
space. You're using -ia with -pj triggers this. It probably isn't what
you want if you intend to use the resulting gamut with collink.
[ Currently "absolute appearance" space uses uses a D50 white point
for tiffgamut, but for collink it uses a "half way" white point
between the source and destination color spaces. I'm not sure
how this difference could be resolved in a clean way. ]
The source image profile was sRGB, destination
profile was printer profile for A-type illuminant. While run "tiffgamut -ir
-pj" before
collink, there is other result - no white point mismatch in diagnostic *.wrl.
Right, because this triggers a "relative" appearance space, that uses the
colorimetric table.
? But I
cannot distinguish the difference between profiles and output TIFFs with
different -i
keys in tiffgamut! The results are rather good, interdependent of tiffgamut -i
key. I
can't understand how must I do linking the best way, with what keys...
Hmm. I'm not sure why that would be the case. Perhaps the white point difference
isn't large enough to result in a visible gamut mapping change.
Graeme Gill.
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