SECTION 5.1
393
Organization and Use of Fonts
Example 5.5
BT
/F13 48 Tf
20 38 Td
7 Tr
( ABC ) Tj
ET
…
Graphics operators to draw a starburst
…
ABC
FIGURE 5.3
Graphics clipped by a glyph path
5.1.3 Glyph Positioning and Metrics
A glyph’s
width—formally,
its
horizontal displacement—is
the amount of space it
occupies along the baseline of a line of text that is written horizontally. In other
words, it is the distance the current text position moves (by translating text space)
when the glyph is painted. Note that the width is distinct from the dimensions of
the glyph outline.
In some fonts, the width is constant; it does not vary from glyph to glyph. Such
fonts are called
fixed-pitch
or
monospaced.
They are used mainly for typewriter-
style printing. However, most fonts used for high-quality typography associate a
different width with each glyph. Such fonts are called
proportional
or
variable-
pitch
fonts. In either case, the
Tj
operator positions the consecutive glyphs of a
string according to their widths.
The width information for each glyph is stored both in the font dictionary and in
the font program itself. (The two sets of widths must be identical; storing this in-
formation in the font dictionary, although redundant, enables a consumer appli-