font.htm

TrueType字库标准文档

the bitmap. this is set by gdi at load time. the<br>
dfbitspointer is guaranteed to be even.<br>
<br>
dfbitsoffset 4 bytes specifying the offset in the file to the<br>
beginning of the bitmap information. if the 04h bit in<br>
the dftype is set, then dfbitsoffset is an absolute<br>
address of the bitmap (probably in rom).<br>
<br>
for raster fonts, dfbitsoffset points to a sequence of<br>
bytes that make up the bitmap of the font, whose height<br>
is the height of the font, and whose width is the sum<br>
of the widths of the characters in the font rounded up<br>
to the next word boundary.<br>
<br>
for vector fonts, it points to a string of bytes or<br>
words (depending on the size of the grid on which the<br>
font was digitized) that specify the strokes for each<br>
character of the font. the dfbitsoffset field must be<br>
even.<br>
<br>
dfreserved 1 byte, not used.<br>
<br>
dfflags 4 bytes specifying the bits flags, which are additional<br>
flags that define the format of the glyph bitmap, as<br>
follows:<br>
<br>
dff_fixed equ 0001h ; font is fixed pitch<br>
dff_proportional equ 0002h ; font is proportional<br>
; pitch<br>
dff_abcfixed equ 0004h ; font is an abc fixed<br>
; font<br>
dff_abcproportional equ 0008h ; font is an abc pro-<br>
; portional font<br>
dff_1color equ 0010h ; font is one color<br>
dff_16color equ 0020h ; font is 16 color<br>
dff_256color equ 0040h ; font is 256 color<br>
dff_rgbcolor equ 0080h ; font is rgb color<br>
<br>
dfaspace 2 bytes specifying the global a space, if any. the<br>
dfaspace is the distance from the current position to<br>
the left edge of the bitmap.<br>
<br>
dfbspace 2 bytes specifying the global b space, if any. the<br>
dfbspace is the width of the character.<br>
<br>
dfcspace 2 bytes specifying the global c space, if any. the<br>
dfcspace is the distance from the right edge of the<br>
bitmap to the new current position. the increment of a<br>
character is the sum of the three spaces. these apply<br>
to all glyphs and is the case for dff_abcfixed.<br>
<br>
dfcolorpointer<br>
4 bytes specifying the offset to the color table for<br>
color fonts, if any. the format of the bits is similar<br>
to a dib, but without the header. that is, the<br>
characters are not split up into disjoint bytes.<br>
instead, they are left intact. if no color table is<br>
needed, this entry is null.<br>
[note: this information is different from that in the<br>
hard-copy developer's notes and reflects a correction.]<br>
<br>
dfreserved1 16 bytes, not used.<br>
[note: this information is different from that in the<br>
hard-copy developer's notes and reflects a correction.]<br>
<br>
dfchartable for raster fonts, the chartable is an array of entries<br>
each consisting of two 2-byte words for windows 2.x and<br>
three 2-byte words for windows 3.00. the first word of<br>
each entry is the character width. the second word of<br>
each entry is the byte offset from the beginning of the<br>
fontinfo structure to the character bitmap. for windows<br>
3.00, the second and third words are used for the<br>
offset.<br>
<br>
there is one extra entry at the end of this table that<br>
describes an absolute-space character. this entry<br>
corresponds to a character that is guaranteed to be<br>
blank; this character is not part of the normal<br>
character set.<br>
<br>
the number of entries in the table is calculated as<br>
((dflastchar - dffirstchar) + 2). this includes a<br>
spare, the sentinel offset mentioned in the following<br>
paragraph.<br>
<br>
for fixed-pitch vector fonts, each 2-byte entry in this<br>
array specifies the offset from the start of the bitmap<br>
to the beginning of the string of stroke specification<br>
units for the character. the number of bytes or words<br>
to be used for a particular character is calculated by<br>
subtracting its entry from the next one, so that there<br>
is a sentinel at the end of the array of values.<br>
<br>
for proportionally spaced vector fonts, each 4-byte<br>
entry is divided into two 2-byte fields. the first<br>
field gives the starting offset from the start of the<br>
bitmap of the character strokes. the second field gives<br>
the pixel width of the character.<br>
<br>
&lt;facename&gt; an ascii character string specifying the name of the<br>
font face. the size of this field is the length of the<br>
string plus a null terminator.<br>
<br>
&lt;devicename&gt; an ascii character string specifying the name of the<br>
device if this font file is for a specific device. the<br>
size of this field is the length of the string plus a<br>
null terminator.<br>
<br>
&lt;bitmaps&gt; this field contains the character bitmap definitions.<br>
each character is stored as a contiguous set of bytes.<br>
(in the old font format, this was not the case.)<br>
<br>
the first byte contains the first 8 bits of the first<br>
scanline (that is, the top line of the character). the<br>
second byte contains the first 8 bits of the second<br>
scanline. this continues until a first &quot;column&quot; is<br>
completely defined.<br>
<br>
the following byte contains the next 8 bits of the<br>
first scanline, padded with zeros on the right if<br>
necessary (and so on, down through the second<br>
&quot;column&quot;). if the glyph is quite narrow, each scanline<br>
is covered by 1 byte, with bits set to zero as<br>
necessary for padding. if the glyph is very wide, a<br>
third or even fourth set of bytes can be present.<br>
<br>
note: the character bitmaps must be stored<br>
contiguously and arranged in ascending order.<br>
<br>
the following is a single-character example, in which<br>
are given the bytes for a 12 x 14 pixel character, as<br>
shown here schematically.<br>
<br>
............<br>
.....**.....<br>
....*..*....<br>
...*....*...<br>
..*......*..<br>
..*......*..<br>
..*......*..<br>
..********..<br>
..*......*..<br>
..*......*..<br>
..*......*..<br>
............<br>
............<br>
............<br>
<br>
the bytes are given here in two sets, because the<br>
character is less than 17 pixels wide.<br>
<br>
00 06 09 10 20 20 20 3f 20 20 20 00 00 00<br>
00 00 00 80 40 40 40 c0 40 40 40 00 00 00<br>
<br>
note that in the second set of bytes, the second digit<br>
of each is always zero. it would correspond to the 13th<br>
through 16th pixels on the right side of the character,<br>
if they were present.<br>
<br>
<br>
the windows 2.x version of dfchartable has a glyphentry structure with<br>
the following format:<br>
<br>
glyphentry struc<br>
gewidth dw ? ; width of character bitmap in pixels<br>
geoffset dw ? ; pointer to the bits<br>
glyphentry ends<br>
<br>
the windows 3.00 version of the dfchartable is dependent on the format<br>
of the glyph bitmap.<br>
<br>
note: the only formats supported in windows 3.00 will be dff_fixed<br>
and dff_proportional.<br>
<br>
dff_fixed<br>
dff_proportional<br>
<br>
glyphentry struc<br>
gewidth dw ? ; width of character bitmap in pixels<br>
geoffset dd ? ; pointer to the bits<br>
glyphentry ends<br>
<br>
dff_abcfixed<br>
dff_abcproportional<br>
<br>
glyphentry struc<br>
gewidth dw ? ; width of character bitmap in pixels<br>
geoffset dd ? ; pointer to the bits<br>
geaspace dd ? ; a space in fractional pixels (16.16)<br>
gebspace dd ? ; b space in fractional pixels (16.16)<br>
gecspace dw ? ; c space in fractional pixels (16.16)<br>
glyphentry ends<br>
<br>
the fractional pixels are expressed as a 32-bit signed number with an<br>
implicit binary point between bits 15 and 16. this is referred to as a<br>
16.16 (&quot;sixteen dot sixteen&quot;) fixed-point number.<br>
<br>
the abc spacing here is the same as that defined above. however, here<br>
there are specific sets for each character.<br>
<br>
dff_1color<br>
dff_16color<br>
dff_256color<br>
dff_rgbcolor<br>
<br>
glyphentry struc<br>
gewidth dw ? ; width of character bitmap in pixels<br>
geoffset dd ? ; pointer to the bits<br>
geheight dw ? ; height of character bitmap in pixels<br>
geaspace dd ? ; a space in fractional pixels (16.16)<br>
gebspace dd ? ; b space in fractional pixels (16.16)<br>
gecspace dd ? ; c space in fractional pixels (16.16)<br>
glyphentry ends<br>
<br>
dff_1color means 8 pixels per byte<br>
dff_16color means 2 pixels per byte<br>
dff_256color means 1 pixel per byte<br>
dff_rgbcolor means rgbquads<br>
<br>
<br>
microsoft is a registered trademark and windows is a trademark of<br>
microsoft corporation.<br>
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