[Openicc] Changing the display whitepoint using the VCGT

Richard Hughes hughsient at gmail.com
Wed Apr 27 13:16:17 PDT 2011

On 27 April 2011 20:18, Chris Murphy <lists at colorremedies.com> wrote:
> Although I regularly see the commercial products with colorimeters unpin the blue channel maximum...

Interesting, thanks.

> Let me know if it makes sense to consider that and I'll do some testing - maybe the user boots into Mac OS X, the display profile is autogenerated, they put that profile up on a network volume or USB stick, reboot to Fedora and install that profile there. Seems like it would work, but I haven't tried it.

Ohh, colord is cleverer than that. It already searches for existing
color profiles on hfs+ disks for the pre-cooked apple profiles for the
machine, and even on fat32 and ntfs partitions in case the user has
profiled it in windows. The user just has to override the
auto-generated profile with the OS X one.

> What is reading the vcgt tag and applying that curve to the video card LUT? Is that colord's responsibility?

colord is just a simple dumb daemon -- it doesn't even known what a
display device looks like. gnome-color-manager creates the xrandr
device, and then creates / assigns it a profile, which is then applied
again by g-c-m if the colord rules match. It's a pretty elegant design
really, as it leaves the session to apply policy in the right place.
See http://colord.hughsie.com/faq.html#gcm for all the logic.

If you want to test GCM and colord without breaking your system, I can
easily put together a Fedora live CD, as it would basically be Fedora
15 and an updated version of gnome-color-manager.


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