[Openicc] questions about Compiz
Hal V. Engel
hvengel at gmail.com
Sun Jan 30 15:38:22 PST 2011
On Sunday, January 30, 2011 01:17:45 pm Jan-Peter Homann wrote:
> Hello Kai-Uwe, Richard and all,
>
> I have following questions about Compiz:
Compiz is a composting system for use with X11. Its job it to compost output
from applications into the display space of what ever screens are in use on a
system. It also supports various on screen effects by using plug ins. Many
plug ins are shipped with Compiz but many others are from 3rd parties.
>
> Wich kind of color transformations are supported from Compiz:
> - RGB 2 RGB
> - CMYK 2 RGB
> - RGB 2 CMYK 2 RGB
Compiz assumes that everything handed to it is device RGB and it does not know
how to do color space transforms at least in the sense we use that terminology
and in it's default state knows nothing about CM.
In order to make Compiz handle color transformations OpenICC had a GSoC
project to write a Compiz plug in named CompICC that converts application
supplied display output (windows, borders, menus, images...) which is always
in RGB format (because the app assumes it is talking to the composting engine)
and transforms this output to device RGB for what ever device that output will
be displayed on and hands this to Compiz to compost onto the display.
>
> Would it be able to implent a rendering to fileout
> - RGB 2 CMYK
> - CMYK 2 CMYK
> (Fast rendering of Bitmaps for Printout)
This is outside of the scope of Compiz since it part of the display pipe line.
>
> What are technical problems and possible solutions for a wide usage of
> Compiz ?
>
The biggest issue with Compiz and composting software is generally the GPU
hardware and drivers which vary in how fast these can do things and also in
how well these implement the high level graphics API that is being used by the
composing engine. In the case of X11 systems and Compiz this is OpenGL.
There is a considerable amount of variation in the quality of current OpenGL
implementations in X11. Some video card drivers have limited (in some case
no) OpenGL support well others have excellent support (nvidia cards with the
proprietary drivers for example). Compiz will run nicely on a high end nvidia
GPU with recent drivers but will not run at all on some older hardware and
with some video card drivers.
The situation is improving as modern GPUs are very powerful (even the less
expensive hardware is powerful relative to what was available a few years ago)
and the quality of the drivers, at least for more recent hardware, has gotten
much better in recent years. For example a few years ago the ATI (now AMD)
X11 drivers where pure crap. After AMD purchased ATI the situation has
changed and their driver is close to nvidia's quality and they are steadily
closing the gap. Open source drivers have also been improving and AMD is
supplying technical support to the open source community (nvidia is not
however) and the open source drivers for this hardware have improved
dramatically in the last few years. Intel actually only supplies open source
drivers for X11 systems for their GPU hardware. Intel GPU hardware is
generally less powerful than nvidia and AMD GPU hardware but their drivers
have generally been very good recently. Side note the video that was recently
talked about here was a presentation by Keith Packard who is one of the
developers of these drivers for Intel.
Compiz or something like it (like kwin) will be used more widely on X11
desktops as all of these things mature. As GPU hardware gets more powerful
and OpenGL support gets better more users will be using a composting system.
>
> Thanks and best regards
> Jan-Peter
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