[compiz] color management spec

Tomas Carnecky tom at dbservice.com
Sat Jun 14 16:38:36 PDT 2008

Owen Taylor wrote:
> If the visual of a window is ARGB, it can't hold XYZ or Lab, or most
> obviously CMYK data.

> difficulties of per-monitor specifics... if I have an image in Adobe RGB
> with 8 bits per primary, it might be interesting to preserve that
> colorspace and use that as the colorspace on my toplevel, but that's not
> done to avoid having colorspace conversion code in the application: it's
> done to avoid losing gamut when converting it to something else.

If you have an image in CMYK the best way to avoid losing gamut, just 
like in your AdobeRGB example, is to let the CM convert it at the very 
last stage. So it might be useful to be able to upload CMYK pixels into 
the xserver and tag the data somehow. I don't see any conflict there as 
long as the application and CM agree on the pixel format.

> Honestly, the only reason this is at all interesting is the limitations
> of RGB 8:8:8. The long term solution here is support for something
> like scRGB (http://en.wikipedia.org/wiki/ScRGB_color_space.)

First the server would have to support buffers with at least 6 byte per 
pixel, which it does not currently. I would love to see support for 
arbitrary pixel formats in the xserver. I would even go as far as having 
the xserver create bare buffers and then tag them with the pixel format 
/ icc profile. After all, if a (OpenGL-based) CM is running the xserver 
doesn't need to know anything about the windows besides the dimensions.


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