User guide

A-15
Appendix
2
1
3
4
6
5
7
8
9
I
A
For the 17
3
nodes 17
3
output R’G’B’ values have to be set in the
3D LUT file. The first triplet describes the output value of the first node,
the second triplet of the second node, and so on.
The numbers (lines) of an RGB node can be calculated with the follow-
ing formula:
In case a particular RGB value of an image’s pixel is not directly de-
scribed through a node, it has to be interpolated: The RGB nodes can
be placed in a spatial graph (cube). Any input RGB value will be de-
scribed by a set of surrounding RGB nodes:
Figure A-1: Surrounding RGB nodes of an undefined input value
With the known look-up (output) values of these eight RGB nodes the
required R’G’B’ value can be calculated (interpolated).
A.5.2 3DL Files
A *.3dl LUT file is a plain ASCII text file that has to match the follow-
ing properties:
– Lines starting with a hash (#) are comments and will not be evalu-
ated.
# of node = 17
2
× index
R
+ 17 × index
G
+ index
B
+1
[ indices range from zero (0) to 16 ]
Example for the node (768, 384, 192):
17
2
×12+17×6+3+1=3574
G
R
B
Undefined example
input value:
(800, 420, 220)
(768, 384, 192) (832, 384, 192)
(768, 448, 192) (832, 448, 192)
(768, 384, 256) (832, 384, 256)
(768, 448, 256) (832, 448, 256)