[Poppler-bugs] [Bug 14526] Poppler incorrectly renders CMYK colors

[bugzilla-daemon at freedesktop.org]

http://bugs.freedesktop.org/show_bug.cgi?id=14526


Brad Hards <bradh at frogmouth.net> changed:

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                 CC|                            |bradh at frogmouth.net




--- Comment #6 from Brad Hards <bradh at frogmouth.net>  2008-02-18 11:39:27 PST ---
I asked Leonard Rosenthal (from Adobe) about this:

Color - what fun ;).

As you know, Poppler/Xpdf uses an explicit algorithm (sometimes called
the "Red book" algorithm, since it comes from the Postscript Red Book)
to convert among the various DeviceXXX color spaces. However Acrobat and
Reader are fully color managed applications, which means that they
ALWAYS associate ICC profiles with DeviceXXX colors and use a CMM to
convert colors as necessary.  Reader users, however, get a "fixed set"
of profiles while Acrobat users are able to change theirs
(Preferences->Color management) - so there are times where even Acrobat
and Reader display different colors when dealing with DeviceCMYK let
alone our apps vs. Poppler/Xpdf.

There is a second potential area involved which is a setting/preference
available in Acrobat & Reader called "overprint preview" which changes
the entire drawing model from a standard "screen" model to one that
simulates "print".  Due to how this works, it's also possible to see
color shifts between the two when this preference is set.

Finally, and I believe we've talked about this one before -
transparency!  When transparency is present in a PDF AND no
"transparency page group" exists, the PDFRef says that the viewer is
free to choose what space to use.  Acrobat/Reader chooses CMYK while
every other viewer sticks with RGB - thus in such PDFs you see a color
shift between our viewers and others.

I would LOVE to see someone add color management (using lcms) to
Poppler/Xpdf!


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