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                                                60
      CHAPTER 3                                                                       Syntax



      a name. For example, in a font dictionary, the value of the Type entry is always
      Font, whereas that of the Subtype entry may be Type1, TrueType, or one of
      several other values.

      The value of the Type entry can almost always be inferred from context. The
      operand of the Tf operator, for example, must be a font object; therefore, the Type
      entry in a font dictionary serves primarily as documentation and as information
      for error checking. The Type entry is not required unless so stated in its
      description; however, if the entry is present, it must have the correct value. In
      addition, the value of the Type entry in any dictionary, even in private data, must
      be either a name defined in this book or a registered name; see Appendix E for
      details.


3.2.7 Stream Objects

      A stream object, like a string object, is a sequence of bytes. However, a PDF
      application can read a stream incrementally, while a string must be read in its
      entirety. Furthermore, a stream can be of unlimited length, whereas a string is
      subject to an implementation limit. For this reason, objects with potentially large
      amounts of data, such as images and page descriptions, are represented as
      streams.

      Note: As with strings, this section describes only the syntax for writing a stream as a
      sequence of bytes. What those bytes represent is determined by the context in which
      the stream is referenced.

      A stream consists of a dictionary followed by zero or more bytes bracketed
      between the keywords stream and endstream:

         dictionary
         stream
         … Zero or more bytes …
         endstream

      All streams must be indirect objects (see Section 3.2.9, “Indirect Objects”) and
      the stream dictionary must be a direct object. The keyword stream that follows
      the stream dictionary should be followed by an end-of-line marker consisting of
      either a carriage return and a line feed or just a line feed, and not by a carriage

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