Kai-Uwe Behrmann wrote:
I forgot to mention value 255 is defined as white in cineon and value 95
as black.
Mapping 255 to white as whitepoint leaves no range above. The used curves
are defined as 8 or 16-bit unsigned integers - no fixpoint. Parametric
curves would be a choice. but I think they are valid for v4 tables only.
Maybe I give it a try.
ICC profile don't define an interchange space. There is a mapping step
(often implicit or loosly defined) between a colorspace encoding, and
the corresponding ICC profile.
Unfortunately not much emphasis is put on this mapping information (At
one stage I had an email from an ICC member claiming that it was in
fact wrong to document such information, since such things are inherently
"device dependent", and none of the ICC standards business).
In practice it helps a lot if there is such a convention, so that ICC
profiles can be interchanged when they deal with the same underlying
device encoded colorspaces. (The confusion as to the polarity of
monochrome profiles is an example of the trouble caused when there
are no standards in this area.)
If there is no established convention, or it is not obvious, then
it's up to you as to how you do this mapping.
Conceptually, most device spaces have an ICC encoding from 0.0 - 1.0.
Internally that may be encoded in the ICC profile as 8 bits, 16 bits,
or some fixed point encoding. This is not directly relevant.
It's up to you how you want to map this to the cineon encoding.
You could map cineon 1023 to ICC 1.0, as long as you had a way
of constructing an appropriate profile (and this is where the
standard tools start letting you down, since almost all of them
assume the media white point is at 1.0).
You could create a complex mapping, mapping 0-255 into ICC 0.0 - 0.5,
and compressing 256-1023 into 0.5 - 1.0, if that suited your purpose.
Graeme Gill.
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