CHAPTER 4
252
Graphics
where the function
g
(x) is defined as
g
(
x
)
=
x
3
108
4
-
-
g
(
x
)
= -------
×
⎛
x
– ----
⎞
841
⎝
29
⎠
6
-
if
x
≥
----
29
otherwise
L*a*b*
space with the CCIR XA/11–
recommended D65 white point. The
a*
and
b*
components, although theoretical-
ly unbounded, are defined to lie in the useful range
−128
to
+127.
Example 4.8
[ /Lab
<< /WhitePoint [ 0.9505 1.0000 1.0890 ]
/Range [
−128
127
−128
127 ]
>>
]
ICCBased Color Spaces
ICCBased
color spaces
(PDF 1.3)
are based on a cross-platform
color profile
as
defined by the International Color Consortium (ICC). Unlike the
CalGray
,
CalRGB
, and
Lab
color spaces, which are characterized by entries in the color
space dictionary, an
ICCBased
color space is characterized by a sequence of bytes
in a standard format. Details of the profile format can be found in the ICC speci-
fication (see the Bibliography).
An
ICCBased
color space is specified as an array:
[ /ICCBased
stream
]
The stream contains the ICC profile. Besides the usual entries common to all
streams (see Table 3.4 on page 62), the profile stream has the additional entries
listed in Table 4.16.