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SECTION 4.5                                                            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
  Table 4.22 and discussion below), which is required to be present.
• 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.

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