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       CHAPTER 4                                                                         Graphics



KEY           TYPE           VALUE

OC            dictionary     (Optional; PDF 1.5) An optional content group or optional content member-
                             ship dictionary (see Section 4.10, “Optional Content”) specifying the option-
                             al content properties for the form XObject. Before the form is processed, its
                             visibility is determined based on this entry. If it is determined to be invisible,
                             the entire form is skipped, as if there were no Do operator to invoke it.

Name          name           (Required in PDF 1.0; optional otherwise) The name by which this form
                             XObject is referenced in the XObject subdictionary of the current resource
                             dictionary (see Section 3.7.2, “Resource Dictionaries”).
                             Note: This entry is obsolescent and its use is no longer recommended. (See
                             implementation note 55 in Appendix H.)

       Example 4.31 shows a simple form XObject that paints a filled square 1000 units
       on each side.

       Example 4.31

          6 0 obj                                  % Form XObject
              << /Type /XObject
                  /Subtype /Form
                  /FormType 1
                  /BBox [ 0 0 1000 1000 ]
                  /Matrix [ 1 0 0 1 0 0 ]
                  /Resources << /ProcSet [ /PDF ] >>
                  /Length 58
              >>
          stream
              0 0 m
              0 1000 l
              1000 1000 l
              1000 0 l
              f
          endstream
          endobj


  4.9.2 Group XObjects

       A group XObject (PDF 1.4) is a special type of form XObject that can be used to
       group graphical elements together as a unit for various purposes. It is distin-
       guished by the presence of the optional Group entry in the form dictionary (see

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