[Openicc] Re: Description of color adjustment tools

[Boudewijn Rempt]

On Monday 13 June 2005 13:50, Jan-Peter Homann wrote:
> Hello Caspar (and Boudewjin)
> I would like to move our dicussion to the openicc mailinglist

I just subscribed -- didn't read all the backlog yet, so maybe I'm spouting 
irrelevant nonsense.

> First I want to understand the actual colormanagement architecture of
> krita. This is something all the other members of the openicc list are
> also interested in.

Well, architecture is a big word. The different colorspaces Krita uses (and 
there are some very weird ones, like one based on Raph Levien's watercolor 
simulation with eight color channels) are implemented as plugin modules. Each 
plugin module implements a number of useful functions, like one to mix 
between colors. 

Conversion between colorspaces is done through lcms. (Wherever possible. The 
Wet & Sticky colorspace, for instance, cannot be handled by lcms, so that's 
first rendered to rgb, and then transformed using sRGB->monitor before 
display.) We cache as many transforms as we can. I have investigated the 
possibility of making Krita flexible enough to enable users to optionally 
swap lcms for another library, but in the end I tought it wasn't needed, so 
lcms is what Krita uses everywhere.

The basics are done:

* Reading/writing profiles to external file formats
* Reading/writing profiles in Krita files (although there's room for  
 improvement here)
* When pasting an image from an external source, the user can apply a 
  profile, when cutting & pasting inside Krita, the image data being
  pasted is transformed before being added to the destination data.
* Images are transformed using the monitor profile for display (but I wish 
  there were some standard location for a calibrated monitor profile).

What's missing:

* Using the monitor profile to transform the data in the color selectors 
 (working on that.)
* Printing is almost non-existent. I'm hoping that there's some library 
  that I can use for that, perhaps from Scribus -> it's on my to-investigate 
  list.
* There's no system-wide place where we can find profiles, so we install
  them ourselves.
* No easy way for users to calibrate their input/output devices.
* Expertise on my part... Color management is not a subject I know much about.

> The second idea is to use abstract profiles and devicelink-profiles as
> universal format for the exchange of coloradjustments.
> This is also very interesting for the other members of the openicc
> mailinglist.

That's Casper's turf, I think. At the moment Krita's gui, the color selectors 
and the tools toolbox demand my attention, and Casper is busy making sure 
Krita can handle any colorspace anyone wants to write a module for, no matter 
the number of channels or the number of bits any individual channel wants.

> So just say hello in the openicc mailinglist, and we will have a fine
> discussion there.

Hello :-).

> PS: In the next weeks and months, i will release three websites
> dedicated to colormanagement-themes managed with drupal.
> Whats about your own site ?

We don't have much beyond the KOffice website at the moment...

-- 
Boudewijn Rempt 
http://www.valdyas.org/fading/index.cgi
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