Image Processing Reference
In-Depth Information
undesirable contours when rendering color sweeps (e.g., tints). In Figure 7.65c and d,
examples of sharp transitions in the round trip accuracy for dark magenta corner
[0 255 0 255] and dark blue corner [255 255 0 255] can be seen, which
can lead to contours. In such cases, smoothing methods should be applied to smooth
out the transitions. Sometimes, these transitions are caused by sparse nodes in the
L*a*b*toCMYK LUT. But, highly dense LUTs can also be built to reduce such
jumps in CMYK formulations and improve roundtrip accuracy. But, higher LUT size
Co
r
ner
s
=
2
55
0
0
2
5
5
Co
r
ner
s
=
2
55
0
0 2
5
5
8
250
K
C
M
Y
7
200
6
5
150
4
100
3
2
50
1
0
0
0
10
20
30
40
50
60
70
80
90 100
0
10
20
30
40
50
60
70
80
90 100
From 0 to gamut corner
From 0 to gamut corner
Corn
er
s = 0
25
5 0 2
5
5
Corne
r
s = 255
0 0
2
55
8
250
K
C
M
Y
7
200
6
5
150
4
100
3
2
50
1
0
0
0
20
40
60
80
100
0
20
40
60
80
100
From 0 to gamut corner
From 0 to gamut corner
Corn
e
rs = 0
0 255
2
55
Corn
e
rs = 0
0 255
255
250
8
K
C
M
Y
7
200
6
5
150
4
100
3
2
50
1
0
0
0
20
40
60
80
100
0
20
40
60
80
100
(c)
From 0 to gamut corner
From 0 to gamut corner
FIGURE 7.65 (continued)
(c) CMYK response (left) and corresponding round trip accur-
acy (right) to dark cyan, dark magenta, dark yellow corners from 100,0,0 print (
'
0
'
on x-axis
corresponds to 100,0,0 point).
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