CHAPTER 4
364
Graphics
for the logical structure hierarchy of one document to refer indirectly to that of
another.
4.10 Optional Content
Optional content (PDF 1.5)
refers to sections of content in a PDF document that
can be selectively viewed or hidden by document authors or consumers. This ca-
pability is useful in items such as CAD drawings, layered artwork, maps, and
multi-language documents.
The following sections describe the PDF structures used to implement optional
content:
•
used to control the visibility of content.
•
al pieces of content in a document may declare themselves as belonging to one
or more optional content groups.
•
tional content groups are set.
4.10.1 Optional Content Groups
An optional content group is a dictionary representing a collection of graphics
that can be made visible or invisible dynamically by users of viewer applications.
The graphics belonging to such a group can reside anywhere in the document:
they need not be consecutive in drawing order, nor even belong to the same con-
tent stream. Table 4.48 shows the entries in an optional content group dictionary.
TABLE 4.48 Entries in an optional content group dictionary
KEY
TYPE
VALUE
Type
name
text string
(Required)
The type of PDF object that this dictionary describes; must be
OCG
for an optional content group dictionary.
(Required)
The name of the optional content group, suitable for presentation in
a viewer application’s user interface.
Name