Sunday, October 28, 2007

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This chapter describes the special facilities in PDF for dealing with text— specifically, for representing characters with glyphs from fonts. A glyph is a graphical shape and is subject to all graphical manipulations, such as coordinate transformation. Because of the importance of text in most page descriptions, PDF provides 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 character 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 position 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 application, or obtained from an external font file.

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PDF Reference, Sixth Edition, version 1.7 (PDF, 31.0M)

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