[argyllcms] Re: Pre-linearization table for BtoA LUT
- From: Graeme Gill <graeme@xxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Fri, 19 Oct 2007 00:43:45 +1000
John Weissberg wrote:
Thanks very much for you explanation. I am sorry to be a bit thicker
than the average. Since our BtoA tables are 16-bit with V2.2 profiles, I
understand that the mapping below (for 8-bit profiles) is not correct:
idx L a b
0 0.00 -128.00 -128.00
1 3.13 -120.03 -120.03
30 93.75 111.06 111.06
31 96.88 119.03 119.03
32 100.00 127.00 127.00
Would it be too much trouble to ask you what the correct mapping is for
a 16-bit LUT?
Simply divide the V2 16 bit range into the resolution of your CLUT.
The V2 16 bit range is listed in table 32 & 33 starting on page 43 of
the V4.2 spec:
Idx L* a* b*
0 0.0000 -128.0000 -128.0000
1 3.1372 -120.0001 -120.0001
2 6.2744 -112.0002 -112.0002
3 9.4116 -104.0004 -104.0004
4 12.5488 -96.0005 -96.0005
5 15.6860 -88.0006 -88.0006
6 18.8232 -80.0007 -80.0007
7 21.9604 -72.0009 -72.0009
8 25.0977 -64.0010 -64.0010
9 28.2349 -56.0011 -56.0011
10 31.3721 -48.0012 -48.0012
11 34.5093 -40.0013 -40.0013
12 37.6465 -32.0015 -32.0015
13 40.7837 -24.0016 -24.0016
14 43.9209 -16.0017 -16.0017
15 47.0581 -8.0018 -8.0018
16 50.1953 -0.0020 -0.0020
17 53.3325 7.9979 7.9979
18 56.4697 15.9978 15.9978
19 59.6069 23.9977 23.9977
20 62.7441 31.9976 31.9976
21 65.8813 39.9974 39.9974
22 69.0186 47.9973 47.9973
23 72.1558 55.9972 55.9972
24 75.2930 63.9971 63.9971
25 78.4302 71.9969 71.9969
26 81.5674 79.9968 79.9968
27 84.7046 87.9967 87.9967
28 87.8418 95.9966 95.9966
29 90.9790 103.9965 103.9965
30 94.1162 111.9963 111.9963
31 97.2534 119.9962 119.9962
32 100.3906 127.9961 127.9961
Graeme Gill.
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