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List:       kde-bugs-dist
Subject:    [digikam] [Bug 386396] Eliminate useless and misleading libpng terminal message
From:       Elle Stone <bugzilla_noreply () kde ! org>
Date:       2017-10-31 18:54:56
Message-ID: bug-386396-17878-LLtYZmhaif () http ! bugs ! kde ! org/
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https://bugs.kde.org/show_bug.cgi?id=386396

--- Comment #1 from Elle Stone <elle@ninedegreesbelow.com> ---
Hmm, digiKam terminal output just printed a useless libpng warning that I've
never seen before:

digikam.dimg: "/hdd/edit/edit/archiveprints/20080416 pond leaves/586-587.png" 
: PNG file identified
libpng warning: iCCP: profile 'ICC profile': 0h: PCS illuminant is not D50

The profile in question is an old Kodak Romm profile directly from the old
Kodak website. Apparently libpng is now checking profile illuminant values, and
complaining about the following discrepancy (using iccToXml to print out the
profile contents:

What is in the old Kodak profile:

      <XYZNumber X="0.96420288" Y="1.00000000" Z="0.82487488"/>

What is in most profile's illuminant field (until iccMAX comes along and makes
it OK to use other illuminants):

      <XYZNumber X="0.96420288" Y="1.00000000" Z="0.82490540"/>

This libpg warning is useless. Users won't know what to do with it. The profile
is fine just as it is. Yes, the D50 illuminant values are slightly off from
what is normally found in V2 and V4 ICC profiles. No, this small difference
won't make a bit of practical difference to the user, especially in a V4 CMM
such as LCMS2 provides. All this warning does is confuse the user (if they see
it) and waste processing time to detect and print.

AFAIK no other file format prints such warnings. As the warnings are about
things that make no difference whatsoever to users, it would be good to disable
the libpng warnings to keep them from being printed to the terminal, where they
might confuse users. In fact they do confuse users, as a search on the internet
will quickly show.

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