The pre and post linearistation curves (or tables as called
in the spec)
for the B2A and A2B tags can contain up to 4096 segments for
mft2
(10.8) CLUT's. And for the embedded cuves (10.5) used by the
v4
lutAtoBType, I found no limitation other than the type of a
uInt32Number
for its segment number.
The more segments the finer of a control is possible.
As well, these curves can contain asymetric numbers of
segments for in/out
or B/M/A elements.
regards
Kai-Uwe Behrmann
--
developing for colour management
www.behrmann.name + www.oyranos.org + www.cinepaint.org
Am 06.08.07, 10:57 +0200 schrieb John Weissberg:
> We are creating BtoA tables for an output (printer
profile):
>
> Input color space: Lab
> Output color space: CMYKOVG
>
> Input Channels = 3
> Output Channels = 7
> CLUT resolution = 33
>
> Total CLUT entries: 33 x 33 x 33 = 35937
>
>
> When we examine other ICC profiles, they all contain 3
extra tables:
>
> 1. 3 x 3 XYZ to XYZ matrix that is normally set to
unity matrix
> 2. Pre-processing matrix for linearizing input Lab
values
> 3. Post-processing matrix for linearizing output ink
values
>
> I am completely baffled by the length requirements for
tables 2 and 3.
>
> When I examine a profile built with Profile Maker 5
(with multi-channel
> option), it used 514 entries in both tables. Other
profiles I have
> checked use 256 entries for these tables.
>
> What are the rules (or rules of thumb) for deciding the
length of these
> pre and post processing matrices?
>
> I have checked the ICC4 spec and found no help there.
>
> --
> John Weissberg
> PerfectProof - Accuracy Made Easy
>
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