CHAPTER 5
410
Text
T
rm
is a temporary matrix; conceptually, it is recomputed before each glyph is
painted during a text-showing operation.
After the glyph is painted, the text matrix is updated according to the glyph dis-
placement and any spacing parameters that apply. First, a combined displacement
is computed, denoted by
t
x
in horizontal writing mode or
t
y
in vertical writing
mode (the variable corresponding to the other writing mode is set to 0):
T
j
t
x
=
⎛ ⎛
w0
– ----------
⎞
×
T
fs
+
T
c
+
T
w
⎞
×
T
h
-
⎝⎝
⎠
1000
⎠
T
j
t
y
=
⎛
w1
– ----------
⎞
×
T
fs
+
T
c
+
T
w
-
⎝
1000
⎠
where
w0
and
w1
are the glyph’s horizontal and vertical displacements
T
j
is a position adjustment specified by a number in a
TJ
array, if any
T
fs
and
T
h
are the current text font size and horizontal scaling parameters in the
graphics state
T
c
and
T
w
are the current character- and word-spacing parameters in the
graphics state, if applicable
The text matrix is then updated as follows:
1
0
t
x
0 0
1 0
t
y
1
T
m
=
×
T
m
5.4 Introduction to Font Data Structures
A font is represented in PDF as a dictionary specifying the type of font, its Post-
Script name, its encoding, and information that can be used to provide a substi-
tute when the font program is not available. Optionally, the font program can be
embedded as a stream object in the PDF file.
The font types are distinguished by the
Subtype
entry in the font dictionary.
composite
fonts;
other types of fonts are called
simple fonts.
In addition to fonts, PDF sup-