CHAPTER 5
5
Text
This chapter describes the special facilities in PDF for dealing with text— specifi-
cally, for representing characters with glyphs from fonts. A glyph is a graphical
shape and is subject to all graphical manipulations, such as coordinate transfor-
mation. Because of the importance of text in most page descriptions, PDF pro-
vides higher-level facilities that permit an application to describe, select, and
render glyphs conveniently and efficiently.
The first section is a general description of how glyphs from fonts are painted on
the page. Subsequent sections cover the following topics in detail:
•
Text state.
A subset of the graphics state parameters pertain to text, including
parameters that select the font, scale the glyphs to an appropriate size, and
accomplish other graphical effects.
•
Text objects and operators.
The text operators specify the glyphs to be painted,
represented by string objects whose values are interpreted as sequences of char-
acter codes. A text object encloses a sequence of text operators and associated
parameters.
•
Font data structures.
Font dictionaries and associated data structures provide
information that a consumer application needs to interpret the text and posi-
tion the glyphs properly. The definitions of the glyphs themselves are contained
in
font programs,
which may be embedded in the PDF file, built into the appli-
cation, or obtained from an external font file.
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