SECTION 9.4
787
Alternate Presentations
tions available for the document.
Note:
Since PDF viewers are not required to support alternate presentations, au-
thors of documents containing alternate presentations should define the files such
that something useful and meaningful can be displayed and printed. For example, if
the document contains an alternate presentation slideshow of a sequence of photo-
graphs, the photographs should be viewable in a static form by viewers that are not
capable of playing the slideshow.
As of PDF 1.5, the only type of alternate presentation is a
slideshow.
Slideshows
are typically invoked by means of JavaScript actions (see “JavaScript Actions” on
robat’s implementation of slideshows.
The following table shows the entries in a slideshow dictionary.
TABLE 9.32 Entries in a slideshow dictionary
KEY
TYPE
VALUE
Type
name
name
name tree
(Required; PDF 1.4)
The type of PDF object that this dictionary describes; must be
SlideShow
for a slideshow dictionary.
(Required; PDF 1.4)
The subtype of the PDF object that this dictionary describes;
must be
Embedded
for a slideshow dictionary.
(Required; PDF 1.4)
A name tree that maps name strings to objects referenced by
the alternate presentation.
Note:
Even though PDF treats the strings in the name tree as strings without a speci-
fied encoding, the slideshow interprets them as UTF-8 encoded Unicode.
Subtype
Resources
StartResource
byte string
(Required; PDF 1.4)
A byte string that must match one of the strings in the
Re-
sources
entry. It defines the root object for the slideshow presentation.
The
Resources
name tree represents a virtual file system to the slideshow. It asso-
ciates strings (“file names”) with PDF objects that represent resources used by the
slideshow. For example, a root stream might reference a file name, which would
be looked up in the
Resources
name tree, and the corresponding object would be
loaded as the file. (This virtual file system is flat; that is, there is no way to refer-
ence subfolders.)