Image Processing Reference
In-Depth Information
140
Mapped
120
100
80
60
40
20
0
0
10
20
30
40
50
60
70
80
90
100
Color number along the ray
Converged
D
E
a
*
values shown for six node colors.
FIGURE 7.58
TABLE 7.13
Out-of-Gamut Color Considered in Figure 7.58
Out of Gamut
Node Colors
L
*
a
*
b
*
1
0.00
0.00
0.00
2
0.12
7.68
54.12
3
0.36
23.59
91.50
4
0.72
46.12
122.55
5
1.19
68.22
150.08
6
1.75
88.88
175.31
7.6.3 S
OFT
G
AMUT
M
APPING WITH
R
AY
-B
ASED
C
ONTROL
M
ODEL
A ray-based control model can be used to implement accurate gamut compression
algorithms, one of which is the soft gamut mapping illustrated below.
Let x
b
be the nearest out-of-gamut color along the ray between the in-gamut
color, x
0
, and the out-of-gamut node color, x
c
. For this discussion, x
c
could be
selected as the color on the boundary of the source color space. This approach is
shown graphically in Figure 7.59 with a dashed curve. All the out-of-gamut colors
between x
0
and x
c
are mapped to the region between x
0
and x
b
nonlinearly inside the
gamut surface using a smooth curve.
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