[gs-bugs] [Bug 691632] New: Default CMYK profile is less than ideal

bugzilla-daemon at ghostscript.com bugzilla-daemon at ghostscript.com
Mon Sep 20 19:50:14 UTC 2010


           Summary: Default CMYK profile is less than ideal
           Product: MuPDF
           Version: unspecified
          Platform: PC
        OS/Version: MacOS X
            Status: NEW
          Severity: normal
          Priority: P4
         Component: fitz
        AssignedTo: tor.andersson at artifex.com
        ReportedBy: jstrother9109 at gmail.com
         QAContact: gs-bugs at ghostscript.com
   Estimated Hours: 0.0

I just did a quick test drive of mupad, and was fairly impressed with the
performance.  However, I tried to open a couple of CMYK PDFs and found that the
color representation was exceedingly poor (in my photos it looks like everyone
is infected with some sort of flesh eating bacteria).

Before you stop me, I recognize that CMYK is device independent and that CMYK
to RGB conversion depends on the profile, my point is that the profile that is
chosen by default may not be the best.

I took a look at the source, and I am honestly not sure what is going on there.
 It looks like cmyktoxyz() converts cmyk to CIE XYZ using some undocumented
color profile, but then those XYZ values are used as RGB values?  It's not
clear to me.

At any rate, it seems to be that the default should use the SWOP profile
(http://www.swop.org/specification), which appears to be the default Adobe CMYK
profile.  This provides a precise transform to CIELAB, which has a precise
transform to RGB.

Of course, just using the SWOP profile won't work perfectly either, since other
people would use different profiles.  But that seems like it would be a much
better default profile then whatever is being used now.

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