SECTION 3.8
155
Common Data Structures
associating the names
F5
,
F6
,
F7
, and
F8
with objects 6, 8, 10, and 12, respectively.
Likewise, the
XObject
subdictionary associates the names
Im1
and
Im2
with
objects 13 and 15, respectively.
Example 3.16
<< /ProcSet [ /PDF /ImageB ]
/Font << /F5 6 0 R
/F6 8 0 R
/F7 10 0 R
/F8 12 0 R
>>
/XObject << /Im1 13 0 R
/Im2 15 0 R
>>
>>
3.8 Common Data Structures
As mentioned at the beginning of this chapter, there are some general-purpose
data structures that are built from the basic object types described in Section 3.2,
data structures for text strings, dates, rectangles, name trees, and number trees.
The subsequent two sections describe more complex data structures for functions
and file specifications.
All of these data structures are meaningful only as part of the document hier-
archy; they cannot appear within content streams. In particular, the special
conventions for interpreting the values of string objects apply only to strings
outside content streams. An entirely different convention is used within content
streams for using strings to select sequences of glyphs to be painted on the page
(see Chapter 5). Table 3.31 summarizes the basic and higher-level data types that
are used throughout this book to describe the values of dictionary entries and
other PDF data values.
TABLE 3.31 PDF data types
TYPE
DESCRIPTION
SECTION
PAGE
ASCII string
array
Bytes containing ASCII characters
Array object