[OpenICC] Oyranos APIs update

[Bob Friesenhahn]

On Wed, 28 Sep 2005, Kai-Uwe Behrmann wrote:
>>
>>> In general, I agree. However, the industry also needs XYZ profiles with
>>> gamma other than 1. For example, the Digital Cinema Distribution master
>>> color space uses XYZ primaries with gamma 2.6.
>>
>> OK if people are going to do things like this with their formats, then they
>> need to support embedded profiles. It's insanity for them to expect people to
>> manually associate an image gamma 2.6 based XYZ profile to their images.
>
> Tagging is nice for single images, like for single stills, but a waste for
> thousand of images. As well heterogenous colour management will allways
> be. There are reasons not to use ICC style CM, even if we wish here to do
> our best to support it.

A trick used in the SPTE DPX format is that there is a 'ditto' flag to 
indicate that the header of the file is similar (as much as possible) 
to the previous frame.  This means that if DPX (or other formats) did 
support an embedded profile, then the 'ditto' flag could be used to 
re-use the already loaded profile.  So I don't think that embedding a 
profile in each frame is really a huge problem.  It is true that if 
the profile were to change, then it would have to be changed in all 
frames.  The profile could be based on an external reference so it is 
not actually embedded in the file.

A bigger problem appears to be with the entire film process which is 
largely based on expert observers who adjust the picture on the fly 
similar to the way an artist works with clay.  Any length of film may 
have somewhat different color characteristics or different conditions 
during the shoot and therefore represents a different colorspace. 
Due to this, while color profiles could be used to help assure 
accurate color reproduction at the hardware level, they don't work 
well for colorspace adjustments to the source image.

Bob
======================================
Bob Friesenhahn
bfriesen at simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/