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                                                            663
       SECTION 8.5                                                                            Actions



       the Rect entry in the annotation with which the URI action is associated). For ex-
       ample, if the mouse coordinates in user space are (xm , ym ) and the annotation
       rectangle extends from (llx , lly ) at the lower-left to (urx , ury ) at the upper-right,
       the final coordinates (xf , yf ) are as follows:

        ( x f = x m – ll x )

        y f = ur y – y m


       If the resulting coordinates (xf , yf ) are fractional, they should be rounded to the
       nearest integer values. They are then appended to the URI to be resolved, separat-
       ed by commas and preceded by a question mark, as shown in this example:

          http : / / www . adobe . com / intro ?100 , 200

       To support URI actions, a PDF document’s catalog (see Section 3.6.1, “Document
       Catalog”) may include a URI entry whose value is a URI dictionary. At the time of
       publication, only one entry is defined for such a dictionary (see Table 8.57).

                                     TABLE 8.57 Entry in a URI dictionary
KEY     TYPE             VALUE

Base    ASCII            (Optional) The base URI to be used in resolving relative URI references. URI actions
        string           within the document may specify URIs in partial form, to be interpreted relative to
                         this base address. If no base URI is specified, such partial URIs are interpreted rela-
                         tive to the location of the document itself. The use of this entry is parallel to that of
                         the body element <BASE >, as described in the HTML 4.01 Specification (see the Bibli-
                         ography).

       The Base entry allows the URI of the document to be recorded in situations in
       which the document may be accessed out of context. For example, if a document
       has been moved to a new location but contains relative links to other documents
       that have not been moved, the Base entry could be used to refer such links to the
       true location of the other documents, rather than that of the moved document.


       Sound Actions

       A sound action (PDF 1.2) plays a sound through the computer’s speakers. Table
       8.58 shows the action dictionary entries specific to this type of action. Sounds are
       discussed in Section 9.2, “Sounds.”

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