SECTION 5.5
427
Simple Fonts
TABLE 5.11 Entries in an encoding dictionary
KEY
TYPE
VALUE
Type
name
name
(Optional)
The type of PDF object that this dictionary describes; if present, must
be
Encoding
for an encoding dictionary.
(Optional)
The
base encoding—that
is, the encoding from which the
Differences
entry (if present) describes differences—specified as the name of a predefined
encoding
MacRomanEncoding
,
MacExpertEncoding
, or
WinAnsiEncoding
(see
If this entry is absent, the
Differences
entry describes differences from an im-
plicit base encoding. For a font program that is embedded in the PDF file, the
implicit base encoding is the font program’s built-in encoding, as described
above and further elaborated in the sections on specific font types below. Other-
wise, for a nonsymbolic font, it is
StandardEncoding
, and for a symbolic font, it
is the font’s built-in encoding.
BaseEncoding
Differences
array
(Optional; not recommended with TrueType fonts)
An array describing the differ-
ences from the encoding specified by
BaseEncoding
or, if
BaseEncoding
is ab-
sent, from an implicit base encoding. The
Differences
array is described below.
The value of the
Differences
entry is an array of character codes and character
names organized as follows:
code
1
name
1,1
name
1,2
…
code
2
name
2,1
name
2,2
…
…
code
n
name
n,1
name
n,2
…
Each code is the first index in a sequence of character codes to be changed. The
first character name after the code becomes the name corresponding to that code.
Subsequent names replace consecutive code indices until the next code appears
in the array or the array ends. These sequences may be specified in any order but
should not overlap.
For example, in the encoding dictionary in Example 5.9, the name
quotesingle
(
'
)
is associated with character code 39,
Adieresis
(
Ä
) with code 128,
Aring
(
Å
) with
129, and
trademark
(
™
) with 170.