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                                       506
CHAPTER 6                                                               Rendering



The colorants or color components represented in a type 5 halftone dictionary
fall into two categories:

• Primary color components for the standard native device color spaces (Gray for
  DeviceGray ; Red, Green, and Blue for DeviceRGB; Cyan, Magenta, Yellow, and
  Black for DeviceCMYK;).
• Nonstandard color components for use as spot colorants in  Separation and
  DeviceN color spaces. Some of these may also be used as process colorants if
  the native color space is nonstandard.

The dictionary must also contain an entry whose key is Default. The value of this
entry is a halftone dictionary to be used for any color component that does not
have an entry of its own.

When a halftone dictionary of some other type appears as the value of an entry in
a type 5 halftone dictionary, it applies only to the single colorant or color com-
ponent named by that entry’s key. This is in contrast to such a dictionary’s being
used as the current halftone parameter in the graphics state, which applies to all
color components. If nonprimary colorants are requested when the current half-
tone is defined by any means other than a type 5 halftone dictionary, the gray
halftone screen and transfer function are used for all such colorants.

Example 6.2 shows a type 5 halftone dictionary with the primary color compo-
nents for a CMYK device. In this example, the halftone dictionaries for the color
components and for the default all use the same spot function.

Example 6.2

  27 0 obj
     << /Type /Halftone
        /HalftoneType 5
        /Cyan 31 0 R
        /Magenta 32 0 R
        /Yellow 33 0 R
        /Black 34 0 R
        /Default 35 0 R
     >>
  endobj

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