Graphics Programs Reference
In-Depth Information
contains entries allowing the cross-reference table—and thus the file's objects—to be
read. Its important entries are summarized in
Table 4-1
.
Table 4-1. Entries in a trailer dictionary (*denotes required entry)
Key
Value type
Value
/Size
*
Integer
Total number of entries in the file's cross-reference table (usually equal to the
number of objects in the file plus one).
/Root
*
Indirect reference to dictionary
The
document catalog
.
/Info
Indirect reference to dictionary
The document's
document information dictionary
.
/ID
Array of two Strings
Uniquely identifies the file within a work flow. The first string is decided when
the file is first created, the second modified by workflow systems when they
modify the file.
Here's an example trailer dictionary:
<<
/Size 421
/Root 377 0 R
/Info 375 0 R
/ID [<75ff22189ceac848dfa2afec93deee03> <057928614d9711db835e000d937095a2>]
>>
Once the trailer dictionary has been processed, we can go on to read the
document
information dictionary
and the
document catalog
.
Document Information Dictionary
The
document information dictionary
contains the creation and modification dates of
the file, together with some simple metadata (not to be confused with the more com-
prehensive XMP metadata discussed in
“XML Metadata” on page 93
).
Document information dictionary entries are described in
Table 4-2
. A typical docu-
ment information dictionary is given in
Example 4-1
.
Table 4-2. Entries in a document information dictionary. The types “text string” and “date string”
are explained later in this chapter.
Key
Value type
Value
/Title
text string
The document's title. Note that this is nothing to do with any title displayed on the first
page.
/Subject
text string
The subject of the document. Again, this is just metadata with no particular rules about
content.
/Keywords
text string
Keywords associated with this document. No advice is given as to how to structure these.
/Author
text string
The name of the author of the document.
/CreationDate
date string
The date the document was created.
