[EMAIL PROTECTED] schrieb:
This seems to cover all cases. v2 having D65, for example, would be reduced
to D50 as media white + a CHAD from D50 to D65. v2 Printer profiles are not
affected.
1. What about "ICC compliant" V2 monitor profiles which "correctly"
record D50 in the wtpt tag, though monitor white is != D50, but which
are so old that they don't contain a CHAD tag yet?
2. What about Graeme's printer profiles, if the printer was not
characterized for D50, but for a different illuminant? My understanding
is, that Graeme's profiles generally (regardless of the deivce type)
record the absolute color of media white (under the actual viewing
illuminant) in the wtpt tag, and in order to establish the tables, he
transforms the measurements (as measured under the actual viewing
illuminant) with a Bradford CAT from absolute media white to D50.
In case (1) the profile does not contain enough information to compute
the "real" absolute colorimetric intent, since no CHAD is present.
In case (2) a "real" absolute colorimetric intent is possible (using the
same strategy as for the 1998 sRGB profile), but an illuminant relative
ICC-absolute intent is not possible, because no information is present
in the profile how the absolute color of media white can be decomposed
into the illuminant and the relative media color (i.e. relative to a
perfect diffuser).
For both cases, the user would IMO need to supply additional information
(e.g. either the CHAD, or at least the illuminant (assuming Bradford)),
in order to make all kinds of transformations (media relative,
illuminant relative, "real" absolute) possible (with correct results).
For instance
cmsCIEXYZ illuminant = {...};
profile_handle = cmsOpenProfileFromFile(...);
cmsAugmentProfileWithIlluminant(profile_handle, &illuminant);
Regards,
Gerhard
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