CHAPTER 4
366
Graphics
an optional content group but rather to an
optional content membership dictio-
nary,
whose entries are shown in Table 4.49. (Section 4.10.2 describes how con-
tent declares its membership in a group or membership dictionary.)
TABLE 4.49 Entries in an optional content membership dictionary
KEY
TYPE
VALUE
Type
name
dictionary or
array
(Required)
The type of PDF object that this dictionary describes; must be
OCMD
for an optional content membership dictionary.
(Optional)
A dictionary or array of dictionaries specifying the optional content
groups whose states determine the visibility of content controlled by this member-
ship dictionary.
Note:
Null values or references to deleted objects are ignored. If this entry is not
present, is an empty array, or contains references only to null or deleted objects, the
membership dictionary has no effect on the visibility of any content.
OCGs
P
name
(Optional)
A name specifying the
visibility policy
for content belonging to this
membership dictionary. Valid values are:
•
AllOn
: visible only if all of the entries in
OCGs
are
ON
•
AnyOn
: visible if any of the entries in
OCGs
are
ON
•
AnyOff
: visible if any of the entries in
OCGs
are
OFF
•
AllOff
: visible only if all of the entries in
OCGs
are
OFF
Default value:
AnyOn
VE
array
(Optional; PDF 1.6)
An array specifying a
visibility expression,
used to compute
visibility of content based on a set of optional content groups; see discussion be-
low.
An optional content membership dictionary can express its visibility policy in
two ways:
•
The
P
entry specifies a simple boolean expression indicating how the optional
content groups specified by the
OCGs
entry determine the visibility of content
controlled by the membership dictionary.
•
PDF 1.6 introduces the
VE
entry, which is a visibility expression that can specify
an arbitrary boolean expression for computing the visibility of content from the
states of optional content groups.