Re: [Openexr-devel] Introduction and CTL/ICC question

[Geraldine Joffre]

On Thu, 10 Mar 2005 22:27:40 +0100 (CET), Kai-Uwe Behrmann wrote
> Am 10.03.05, 12:02 -0800 schrieb Joseph Goldstone:
> > Were you serious about wanting a parameterized form for color primaries,
> > matrices and gamma values, or was that rhetorical, with the real weight of
> > your request concerning tone reproduction curves and the shaper LUTs 
> > expressed
> > as a component of the lut16Type, lut8Type, lutAtoBType and lutBtoAType
> > encodings?
>  
> My question included tone reproduction as well as profiles 
> for content manipulation. While ICC CMMs usualy work with CLUTs or 
> lattices (except display profiles), matrix based profiles often 
> could very elegant express the same. Faced for instance with the 
> imprecission of CLUT based profiles for large gamut differences, the 
> matrix approach seems plausible.

I am under the impression that what you are after is the ability to handle tone 
and color 
reproduction of HDR images via ICC profiles. Is this correct? In this case, you 
may want to 
consider the following points:

1. Existing tone reproduction techniques for HDR images are using parameters 
that depend on 
the characteristic of the image processed, i.e. vary from image to image 
depending on the pixel 
values. I don't see how such parameters could be stored in an ICC profile. 

2. AFAIK, the main purpose of ICC profiles is to facilitate communicate between 
imaging 
devices, but imaging devices are still low dynamic range (expect maybe a few 
exception for 
high-end display devices but it will take some time before their use become 
widespread). Sure, 
ICC profiles can also be used as abstract profiles but the structure was 
primarily designed for 
the needs of device profiles, for which the complexity lies in color gamut 
mapping rather than 
tone mapping.

I'm not saying it isn't worthwile exploring this, I just want to point out some 
issues regarding 
the use of the ICC profiles mechanism for HDR imaging.


Geraldine Joffre
MultimediaPhoto Sarl
http://www.hdrsoft.com