[Openicc] Questions about ... CM for Displays

[Jan-Peter Homann]

Hello list,
Concerning colormanagement to the display, we have following use cases:
1) all content shown on the display has the same colorspace e.g. sRGB
This could be colormanagemed by LUTS in the Video-Card or in in the monitor

2) different windows showing content in differnt colorspace
This could be colormanagement by the Desktop (e.g. KDE or Gnome)

3) Complex documents are presented in a window. But the objects have 
different profiles
This must be colormanagemed by the application itself (e.g. Layout 
application or PDF viewer)

If we are thinking abou a colormanagement architecture, we always have 
to look how this three cases work together.

Regards
Jan-Peter

PS: Similar, but even more complicated is the colormanagement 
architecture for the printing-chain...



Hal V. Engel wrote:
> I think for the most part that everyone here agrees with this in 
> principle.
> Your example of 8 bit source images on a high bit depth (and perhaps wide 
> gamut) display is probably the most illuminating example since most 
> applications other than those that are color management aware will 
> effectively be doing everything in 8 bit sRGB (IE. not specifying a color 
> space).  On a wide gamut display X11 would map these sRGB colors by way of a 
> color transform into a smaller gamut than the displays full gamut in order to 
> correctly display the application and it's contents.  Most applications would 
> work perfectly well in this scenario and would need nothing else.  For 
> example,  this would handle the browser example that Chris brought up very 
> nicely.
>
> The simple case of CM dumb applications being color managed as sRGB to the 
> display color space should not be overly difficult to implement.  Although I 
> don't think it would be trivial either.  But when you start adding things 
> like applications being able to specify the color space and rendering intents 
> for specific content (IE. specific parts of the display area to color manage 
> differently) things become more difficult.  Not imposable mind you just more 
> difficult.
>
> As a starting point X11 needs to manage the video card LUT.  We can currently 
> specify a per display ICC profile atom that X11 can track after this has been 
> set after start up.  But this needs to be persistant so that X11 
> automatically retains this information when it is restarted.   That is as a 
> user I should be able to set this someplace and X11 should retain and use 
> this information until it has been changed by the user.
>
> In addition X11 should to be extended to have LUT loader functionality or at 
> least to allow users to specify a LUT loader that X11 calls at start up or 
> when ever the ICC profile atom is changed so that it not only keeps track of 
> the profiles that have been setup but also automatically loads the video card 
> LUTs when needed.  I would like to see this support both normal video card 
> gamma tags in profiles and ArgyllCMS style calibration files.
>
> As a user I would be happy with some new options in the xorg.conf file where I 
> could specify the above items.   I also should add that this functionality 
> would be fairly simple to implement and could conceiveably be in version 1.5 
> or 1.6 of the X11 server.
>
> On the other hand unlike the LUTs in video cards which are volatile the LUTs 
> in LCD monitors appear to be persistant (if I am wrong about this please 
> correct me).  So I don't think X11 has a role in this area since I think this 
> should be handled by the monitor calibration software.  Unless you are also 
> proposing that X11 should have monitor calibration functionality.   But I 
> don't think this is what you had in mind.
>
> What I am getting at is that X11 needs to work into being fully color managed 
> in a systematic way by first supporting full management of the video card 
> LUTs (this would actaully be a step up from what current versions of Windows 
> Vista do in this area) and then later on putting in place basic sRGB to 
> display color management with an opt out option for applications that are CM 
> aware.  This would make X11 more advanced in this area than any other 
> windowing system in existance.   Later still X11 could add hooks for CM aware 
> applications to have control over content color space and rendering intent 
> but with X11 handling the content to display color transformation functions.
>
> Of course there are other CM related things that need work in X11 as well.  
> For example we have had exchanges on this list as well as the xorg list about 
> XV by passing the video card LUTs.  This and anything like this will need to 
> be fixed at some point.
>
> Hal
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>
>   


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