SECTION 4.9
363
Form XObjects
Printing Reference XObjects
When printing a page containing reference XObjects, an application may emit
any of the following items, depending on the capabilities of the application, the
user’s preferences, and the nature of the print job:
•
The imported content designated by the reference XObject
•
The reference XObject as a proxy for the imported content
•
An OPI proxy or substitute image taken from the reference XObject’s OPI dic-
tionary, if any (see Section 10.10.6, “Open Prepress Interface (OPI)”)
The imported content or the reference XObject may also be emitted in place of an
OPI proxy when generating OPI comments in a PostScript output stream.
Special Considerations
Certain special considerations arise when reference XObjects interact with other
PDF features:
•
When the page imported by a reference XObject contains annotations (see Sec-
visible appearance stream (Section 8.4.4, “Appearance Streams”) must be in-
cluded in the rendering of the imported page. If the proxy is a snapshot image
of the imported page, it must also include the annotation appearances. These
appearances must therefore be converted into part of the proxy’s content
stream, either as subsidiary form XObjects or by flattening them directly into
the content stream.
•
Logical structure information associated with a page (see Section 10.6, “Logical
document with a reference XObject. In a target document with multiple pages,
structure elements occurring on the imported page are typically part of a larger
structure pertaining to the document as a whole; such elements cannot mean-
ingfully be incorporated into the structure of the containing document. In a
one-page target document or one made up of independent, structurally unre-
lated pages, the logical structure for the imported page may be wholly self-con-
tained; in this case, it may be possible to incorporate this structure information
into that of the containing document. However, PDF provides no mechanism