The 'post' table

General table information

The 'post' table contains information needed to use a TrueType font on a PostScript printer. It contains the data needed for the FontInfo dictionary entry as well as the PostScript names for all of the glyphs in the font. It also contains memory usage information needed by the PostScript driver for memory management.

The 'post' table is documented in Table 72 below. The first item specifies the table format. There are five possibilities: format 1, format 2, format 2.5, format 3 and format 4. Each version is documented below. Only formats 2, 2.5 and 4 require subtables.

Table 72: 'post' table
Type Name Description
Fixed format Format of this table
Fixed italicAngle Italic angle in degrees
FWord underlinePosition Underline position
FWord underlineThickness Underline thickness
uint16 isFixedPitch Font is monospaced; set to 1 if the font is monospaced and 0 otherwise
uint16 reserved Reserved, set to 0
uint32 minMemType42 Minimum memory usage when a TrueType font is downloaded as a Type 42 font
uint32 maxMemType42 Maximum memory usage when a TrueType font is downloaded as a Type 42 font
uint32 minMemType1 Minimum memory usage when a TrueType font is downloaded as a Type 1 font
uint32 maxMemType1 Maximum memory usage when a TrueType font is downloaded as a Type 1 font

The isFixedPitch flag is used to indicate that the font is monospaced. A monospaced font is one in which all glyphs have the same horizontal width at all point sizes (that is, in the 'hmtx' and 'hdmx' tables), or have zero width. A monospaced font will also have to have the maximum width field in the 'hhea' table set appropriately. Note that on the Mac OS, it is also necessary to make sure that glyph widths from 'NFNT' bitmap fonts are consistent with the monospaced metrics in the TrueType font.

The entries minMemType42, maxMemType42, minMemType1, and maxMemType1 are necessary because PostScript drivers can do better memory management if the virtual memory requirements of a downloadable TrueType font are known before the font is downloaded. This information should be supplied if known. If it is not known, set the values to zero.

Maximum memory usage is minimum memory usage plus maximum runtime memory use. Maximum runtime memory use depends on the maximum band size of any bitmap potentially rasterized by the TrueType font scaler. Runtime memory usage could be calculated by rendering characters at different point sizes and comparing the memory use.

The memory usage of a downloaded TrueType font will vary with whether it is defined as a TrueType or Type 1 font on the printer. Minimum memory usage can be calculated by calling VMStatus, downloading the font, and calling VMStatus a second time.

'post' Format 1

The order in which glyphs are placed in a font is at the convenience of the font developer To use format 1, a font must contain exactly the 258 glyphs in the standard Macintosh ordering. For such fonts, the glyph names are taken from the system. As a result, this format does not require a special subtable.

The names for these 258 glyphs are, in order:

Glyph ID Name
0 .notdef
1 .null
2 nonmarkingreturn
3 space
4 exclam
5 quotedbl
6 numbersign
7 dollar
8 percent
9 ampersand
10 quotesingle
11 parenleft
12 parenright
13 asterisk
14 plus
15 comma
16 hyphen
17 period
18 slash
19 zero
20 one
21 two
22 three
23 four
24 five
25 six
26 seven
27 eight
28 nine
29 colon
30 semicolon
31 less
32 equal
33 greater
34 question
35 at
36 A
37 B
38 C
39 D
40 E
41 F
42 G
43 H
44 I
45 J
46 K
47 L
48 M
49 N
50 O
51 P
52 Q
53 R
54 S
55 T
56 U
57 V
58 W
59 X
60 Y
61 Z
62 bracketleft
63 backslash
64 bracketright
65 asciicircum
66 underscore
67 grave
68 a
69 b
70 c
71 d
72 e
73 f
74 g
75 h
76 i
77 j
78 k
79 l
80 m
81 n
82 o
83 p
84 q
85 r
86 s
87 t
88 u
89 v
90 w
91 x
92 y
93 z
94 braceleft
95 bar
96 braceright
97 asciitilde
98 Adieresis
99 Aring
100 Ccedilla
101 Eacute
102 Ntilde
103 Odieresis
104 Udieresis
105 aacute
106 agrave
107 acircumflex
108 adieresis
109 atilde
110 aring
111 ccedilla
112 eacute
113 egrave
114 ecircumflex
115 edieresis
116 iacute
117 igrave
118 icircumflex
119 idieresis
120 ntilde
121 oacute
122 ograve
123 ocircumflex
124 odieresis
125 otilde
126 uacute
127 ugrave
128 ucircumflex
129 udieresis
130 dagger
131 degree
132 cent
133 sterling
134 section
135 bullet
136 paragraph
137 germandbls
138 registered
139 copyright
140 trademark
141 acute
142 dieresis
143 notequal
144 AE
145 Oslash
146 infinity
147 plusminus
148 lessequal
149 greaterequal
150 yen
151 mu
152 partialdiff
153 summation
154 product
155 pi
156 integral
157 ordfeminine
158 ordmasculine
159 Omega
160 ae
161 oslash
162 questiondown
163 exclamdown
164 logicalnot
165 radical
166 florin
167 approxequal
168 Delta
169 guillemotleft
170 guillemotright
171 ellipsis
172 nonbreakingspace
173 Agrave
174 Atilde
175 Otilde
176 OE
177 oe
178 endash
179 emdash
180 quotedblleft
181 quotedblright
182 quoteleft
183 quoteright
184 divide
185 lozenge
186 ydieresis
187 Ydieresis
188 fraction
189 currency
190 guilsinglleft
191 guilsinglright
192 fi
193 fl
194 daggerdbl
195 periodcentered
196 quotesinglbase
197 quotedblbase
198 perthousand
199 Acircumflex
200 Ecircumflex
201 Aacute
202 Edieresis
203 Egrave
204 Iacute
205 Icircumflex
206 Idieresis
207 Igrave
208 Oacute
209 Ocircumflex
210 apple
211 Ograve
212 Uacute
213 Ucircumflex
214 Ugrave
215 dotlessi
216 circumflex
217 tilde
218 macron
219 breve
220 dotaccent
221 ring
222 cedilla
223 hungarumlaut
224 ogonek
225 caron
226 Lslash
227 lslash
228 Scaron
229 scaron
230 Zcaron
231 zcaron
232 brokenbar
233 Eth
234 eth
235 Yacute
236 yacute
237 Thorn
238 thorn
239 minus
240 multiply
241 onesuperior
242 twosuperior
243 threesuperior
244 onehalf
245 onequarter
246 threequarters
247 franc
248 Gbreve
249 gbreve
250 Idotaccent
251 Scedilla
252 scedilla
253 Cacute
254 cacute
255 Ccaron
256 ccaron
257 dcroat

When Mac OS 8.5 was released, the MacRoman character set was redefined to replace the Universal Currency Symbol with the Euro. The standard Macintosh ordering of glyphs was not updated, however, in order to avoid breaking fonts and software that used it. Font vendors should update their fonts as possible to include the Euro for proper functioning on Mac OS 8.5 and later. Fonts with the Euro cannot use 'post' formats 1 or 2.5.

'post' Format 2

Format 2 is used for fonts that contain some glyphs not in the standard set or whose glyph ordering is non-standard. The glyph name index array in this subtable maps the glyphs in this font to a name index. If the name index is between 0 and 257, treat the name index as a glyph index in the Macintosh standard order. If the name index is between 258 and 32767, then subtract 258 and use that to index into the list of Pascal strings at the end of the table. In this manner a font may map some of its glyphs to the standard glyph names, and some to its own names.

Index numbers 32768 through 65535 are reserved for future use. If you do not want to associate a PostScript name with a particular glyph, use index number 0 which points to the name .notdef.

Note that the numberOfGlyphs field must be equal to the numGlyphs field of the 'maxp' (Maximum Profile) table.

Table 73: 'post' format 2
Type Name Description
uint16 numberOfGlyphs number of glyphs
uint16 glyphNameIndex[numberOfGlyphs] Ordinal number of this glyph in 'post' string tables. This is not an offset.
Pascal string names[numberNewGlyphs] glyph names with length bytes [variable] (a Pascal string)

 

'post' Format 2.5

Format 2.5 is a space saving format for fonts which contain a pure subset of the standard glyph set or which contain a reordering of the standard set. This format is useful for fonts that contain only glyphs in the standard Apple glyph set but which have those glyphs arranged in a non-standard order or fonts which are missing some glyphs. The table contains one byte for each glyph in the font. The byte is treated as a signed offset that maps the glyph index used in this font into the standard glyph index. For example, assume that the font contains the three glyphs A, B, and C. Assume that C appears first, B second and A third. These glyphs are the 37th, 38th, and 39th glyphs in the standard ordering. The 'post' table would contain the bytes +39, +37, +35 because:

offset[0] indexes C and 0 + 39 = 39 the standard index for C

offset[1] indexes B and 1 + 37 = 38 the standard index for B

offset[2] indexes A and 2 + 35 = 37 the standard index for A

Note that the numberOfGlyphs field must be equal to the numGlyphs field of the 'maxp' (Maximum Profile) table.

Table 74: 'post' Format 2.5
Type Name Description
uint16 numberOfGlyphs Number of glyphs
int8 offset[number of glyphs] Difference between graphic index and standard order of glyph

When Mac OS 8.5 was released, the MacRoman character set was redefined to replace the Universal Currency Symbol with the Euro. The standard Macintosh ordering of glyphs was not updated, however, in order to avoid breaking fonts and software that used it. Font vendors should update their fonts as possible to include the Euro for proper functioning on Mac OS 8.5 and later. Fonts with the Euro cannot use 'post' formats 1 or 2.5.

 As of February 2000, use the 'post' format 2.5 is deprecated. Font vendors should not put 'post' tables in their fonts using format 2.5 and should convert existing fonts to different 'post' table formats.

'post' Format 3

Format 3 makes it possible to create a special font that is not burdened with a large 'post' table set of glyph names. This format specifies that no PostScript name information is provided for the glyphs in this font. The printing behavior of this format on PostScript printers is unspecified, except that it should not result in a fatal or unrecoverable error. Some drivers may print nothing, other drivers may attempt to print using a default naming scheme. This format does not require a special subtable.

 

'post' Format 4

Composite fonts on Japanese, Chinese or Korean printers work only with character codes. QuickDraw GX printer drivers only know about glyph index values. The TrueType scaler uses format 4 'post' table to reencode a font that maps to a composite font on a printer. This encoding consists of naming the glyphs by using their character codes. The driver has PostScript code that knows how to take this ASCII string, strip the leading "a," and convert the rest to hexadecimal. The resulting hexadecimal number is the character code of the glyph. In this manner, the composite fonts on the printer are used.

Any font that maps to a composite font on the printer needs to include a format 4 'post' table. The structure of a format 4 'post' table is as follows: the 'post' table header is followed by an array of uint16 values. An entry for every glyph is required. The index into the array is the glyph index. The data in the array is the character code that maps to that glyph, or 0xFFFF if there is no associated character code for that glyph.

Mac OS-specific information

The 'post' table is required on the Mac OS. On versions of the Mac OS prior to OS X, none of the information in the 'post' table header other than the format field is used by the OS. This information may, however, be used by other font rendering applications.

Newton-specific information

The 'post' table is not required on the Newton.

Dependencies

If a 'post' table implies a number of glyphs in the font—which is true for every 'post' table format other than 3—the number of glyphs in the font implied by the 'post' table must match the number of glyphs found in the Maximum Profile ('maxp') table.

Tools

Editing of the 'post' table is possible indirectly using DumpPOST and either FusePOST or the AAT Font Tool to put the changed data back into the font. In particular, the 'post' table cannot be currently edited using TrueEdit.

Note that both FusePOST and the AAT Font Tool will produce the optimum 'post' table format for your font. They do not allow the user to specify the 'post' table format to use
.

Change Log

10 November 2000
Fixed the size of the isFixedPitch field of the header..
7 April 2000
Clarified the meaning of the isFixedPitch field of the header.
16 February 2000
Deprecated 'post' format 2.5.
4 February 2000
Added the standard Macintosh glyph names for 'post' format 1.
18 January 2000
Clarified interpretation of numberOfGlyphs fields for 'post' formats 2 and 2.5.
1 October 1996
Created unified TrueType book.
applefonts@apple.com

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