SECTION 4.5
273
Color Spaces
For color spaces that have a value of
NChannel
for the
Subtype
entry in the at-
tributes dictionary (see Table 4.21), the following restrictions apply to process
colors:
•
There can be color components from at most one process color space, which
can be any device or CIE-based color space.
•
For a non-CMYK color space, the names of the process components must ap-
pear sequentially in the
names
array, in the normal color space order (for exam-
ple,
Red
,
Green
, and
Blue
). However, the names in the
names
array need not
match the actual color space names (for example, a
Red
component need not be
named
Red
).The mapping of names is specified in the process dictionary (see
•
Definitions for process colorants should not appear in the colorants dictionary.
Any such definition should be ignored if the colorant is also present in the pro-
cess dictionary. Any component not specified in the process dictionary is con-
sidered to be a spot colorant.
•
For a
CMYK
color space, a subset of the components may be present, and they
may appear in any order in the
names
array. The reserved names
Cyan
,
Magenta
,
Yellow
, and
Black
are always considered to be process colors, which
do not necessarily correspond to the colorants of a specific device; they are not
required to have entries in the process dictionary.
•
The values associated with the process components must be stored in their nat-
ural form (that is, subtractive color values for
CMYK
and additive color values
for
RGB),
since they are interpreted directly as process values by consumers
making use of the process dictionary. (For additive color spaces, this is the re-
verse of how color values are specified for
DeviceN
, as described above in the
discussion of the
names
parameter.)
The
MixingHints
entry in the attributes dictionary specifies a
mixing hints dictio-
nary
(see Table 4.23) that provides information about the characteristics of colo-
rants that can be used in blending calculations when the actual colorants are not
available on the target device. Applications are not required to use this informa-
tion.