[cairo-bugs] [Bug 96583] New: Unwanted color space conversion done by OS X

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=96583

            Bug ID: 96583
           Summary: Unwanted color space conversion done by OS X
           Product: cairo
           Version: unspecified
          Hardware: x86-64 (AMD64)
                OS: Mac OS X (All)
            Status: NEW
          Severity: normal
          Priority: medium
         Component: quartz backend
          Assignee: vladimir at pobox.com
          Reporter: ar2988-gim at yahoo.co.uk
        QA Contact: cairo-bugs at cairographics.org

I am opening this ticket because display color management by Gimp under Mac OS
X 10.8 or later, is incorrect. It appears that this issue goes back to the
cairo quartz backend, used by Gimp.

As I understand it, cairo does not do any color management. The intended
behavior of cairo is that it passes on the colors unchanged to the display.

This is what appears to be happening under Mac OS X. The display always has a
color profile. By default, the OS creates the profile from the gamma and
primary information in the EDID. The OS always color manages the display. From
the cairo manual on quartz surfaces: "The surface is created using the Device
RGB (or Device Gray, for A8) color space." Up to OS X 10.7, Device RGB was, in
effect, the monitor color space. From OS X 10.8, Device RGB is sRGB. The
intended behavior of cairo has been derailed by this change. We get an unwanted
conversion from sRGB to the display profile, done by the OS.

So the fix would be to modify the system call so that the surface is definitely
in the monitor color space.

Versions: I do not know which version of cairo was used to build Gimp 2.8.16.
My OS version is 10.9.5.

Unfortunately I don't know how I could test any fix that might be proposed. I
am a user of Gimp who noted the display color management issue; and who
eventually discovered, with a hint from a Gimp developer, that the issue
appears to go back to the cairo quartz backend. Other than that, I have no
experience of Gimp or cairo development (least of all, building working
binaries). My original bug report on Gimp is here:
https://bugzilla.gnome.org/show_bug.cgi?id=739989

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