Chip 2001 August - Disc 2/chip_20018102_hu.iso/linux/X-4.1.0/doc/bdf.txt

Text File | 2001-06-27 | 8.7 KB | 529 lines

         Bitmap Distribution Format

            Version 2.1

           X Consortium Standard

         X Version 11, Release 6.4



Copyright 1984, 1987, 1988 Adobe Systems, Inc.

Permission to use, copy, modify, and distribute this soft-
ware and its documentation for any purpose and without fee
is hereby granted, provided that the above copyright notice
appear in all copies and that both that copyright notice and
this permission notice appear in supporting documentation.





The Bitmap Distribution Format (BDF), Version 2.1, is an X
Consortium standard for font interchange, intended to be
easily understood by both humans and computers.

File Format

Character bitmap information will be distributed in an
USASCII-encoded, human-readable form.  Each file is encoded
in the printable characters (octal 40 through 176) of
USASCII plus carriage return and linefeed.  Each file con-
sists of a sequence of variable-length lines.  Each line is
terminated either by a carriage return (octal 015) and line-
feed (octal 012) or by just a linefeed.

The information about a particular family and face at one
size and orientation will be contained in one file.  The
file begins with information pertaining to the face as a
whole, followed by the information and bitmaps for the indi-
vidual characters.

A font bitmap description file has the following general
form, where each item is contained on a separate line of
text in the file.  Tokens on a line are separated by spaces.
Keywords are in upper case, and must appear in upper case in
the file.

1.   The word STARTFONT followed by a version number indi-
     cating the exact file format used.  The version
     described here is 2.1.










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2.   Lines beginning with the word COMMENT may appear any-
     where between the STARTFONT line and the ENDFONT line.
     These lines are ignored by font compilers.

3.   The word FONT followed by either the XLFD font name (as
     specified in part III) or some private font name.    Cre-
     ators of private font name syntaxes are encouraged to
     register unique font name prefixes with the X Consor-
     tium to prevent naming conflicts.    Note that the name
     continues all the way to the end of the line and may
     contain spaces.

4.   The word SIZE followed by the point size of the charac-
     ters, the x resolution, and the y resolution of the
     device for which these characters were intended.

5.   The word FONTBOUNDINGBOX followed by the width in x,
     height in y, and the x and y displacement of the lower
     left corner from the origin.  (See the examples in the
     next section.)

6.   Optionally, the word STARTPROPERTIES followed by the
     number of properties (p) that follow.

7.   Then come p lines consisting of a word for the property
     name followed by either an integer or string surrounded
     by double-quote (octal 042).  Internal double-quote
     characters are indicated by using two in a row.

     Properties named FONT_ASCENT, FONT_DESCENT, and
     DEFAULT_CHAR should be provided to define the logical
     font-ascent and font-descent and the default-char for
     the font.    These properties will be removed from the
     actual font properties in the binary form produced by a
     compiler.    If these properties are not provided, a com-
     piler may reject the font or may compute (arbitrary)
     values for these properties.

8.   The property section, if it exists, is terminated by
     ENDPROPERTIES.

9.   The word CHARS followed by the number of character seg-
     ments (c) that follow.

10.  Then come c character segments of the form:

     a.   The word STARTCHAR followed by up to 14 characters
      (no blanks) of descriptive name of the glyph.

     b.   The word ENCODING followed by one of the following
      forms:

      i.   <n> - the glyph index, that is, a positive
           integer representing the character code used









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           to access the glyph in X requests, as defined
           by the encoded character set given by the
           CHARSET_REGISTRY-CHARSET_ENCODING font prop-
           erties for XLFD conforming fonts.  If these
           XLFD font properties are not defined, the
           encoding scheme is font-dependent.

      ii.  -1 <n> - equivalent to form above.  This syn-
           tax is provided for backward compatibility
           with previous versions of this specification
           and is not recommended for use with new
           fonts.

      iii. -1 - an unencoded glyph.  Some font compilers
           may discard unencoded glyphs, but, in gen-
           eral, the glyph names may be used by font
           compilers and X servers to implement dynamic
           mapping of glyph repertoires to character
           encodings as seen through the X protocol.

     c.   The word SWIDTH followed by the scalable width in
      x and y of character.  Scalable widths are in
      units of 1/1000th of the size of the character.
      If the size of the character is p points, the
      width information must be scaled by p/1000 to get
      the width of the character in printer's points.
      This width information should be considered as a
      vector indicating the position of the next charac-
      ter's origin relative to the origin of this char-
      acter.  To convert the scalable width to the width
      in device pixels, multiply SWIDTH times p/1000
      times r/72, where r is the device resolution in
      pixels per inch.  The result is a real number giv-
      ing the ideal print width in device pixels.  The
      actual device width must of course be an integral
      number of device pixels and is given in the next
      entry.  The SWIDTH y value should always be zero
      for a standard X font.

     d.   The word DWIDTH followed by the width in x and y
      of the character in device units.  Like the
      SWIDTH, this width information is a vector indi-
      cating the position of the next character's origin
      relative to the origin of this character.  Note
      that the DWIDTH of a given ``hand-tuned'' WYSIWYG
      glyph may deviate slightly from its ideal device-
      independent width given by SWIDTH in order to
      improve its typographic characteristics on a dis-
      play.  The DWIDTH y value should always be zero
      for a standard X font.

     e.   The word BBX followed by the width in x (BBw),
      height in y (BBh), and x and y displacement (BBox,
      BBoy) of the lower left corner from the origin of









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      the character.

     f.   The optional word ATTRIBUTES followed by the
      attributes as 4 hex-encoded characters.  The
      interpretation of these attributes is undefined in
      this document.

     g.   The word BITMAP.

     h.   h lines of hex-encoded bitmap, padded on the right
      with zeros to the nearest byte (that is, multiple
      of 8).

     i.   The word ENDCHAR.

11.  The file is terminated with the word ENDFONT.

Metric Information

Figures 1 and 2 best illustrate the bitmap format and char-
acter metric information.










































                 -5-

































      BBw = 9, BBh = 22, BBox = -2, BBoy = -6
            DWIDTH = 8 0
               SWIDTH = 355 0
         ``+'' = character origin and width

        Figure 1: An example of a descender


























                 -6-

































      BBh = 6, BBw = 4, BBox = +2, BBoy = +12
            DWIDTH = 5 0
               SWIDTH = 223 0

Figure 2: An example with the origin outside the bounding box



























                 -7-


An Example File

The following is an abbreviated example of a bitmap file
containing the specification of two characters (the j and
quoteright in figures 1 and 2).


     STARTFONT 2.1
     COMMENT This is a sample font in 2.1 format.
     FONT -Adobe-Helvetica-Bold-R-Normal--24-240-75-75-P-65-ISO8859-1
     SIZE 24 75 75
     FONTBOUNDINGBOX 9 24 -2 -6
     STARTPROPERTIES 19
     FOUNDRY "Adobe"
     FAMILY "Helvetica"
     WEIGHT_NAME "Bold"
     SLANT "R"
     SETWIDTH_NAME "Normal"
     ADD_STYLE_NAME ""
     PIXEL_SIZE 24
     POINT_SIZE 240
     RESOLUTION_X 75
     RESOLUTION_Y 75
     SPACING "P"
     AVERAGE_WIDTH 65
     CHARSET_REGISTRY "ISO8859"
     CHARSET_ENCODING "1"
     MIN_SPACE 4
     FONT_ASCENT 21
     FONT_DESCENT 7
     COPYRIGHT "Copyright (c) 1987 Adobe Systems, Inc."
     NOTICE "Helvetica is a registered trademark of Linotype Inc."
     ENDPROPERTIES
     CHARS 2
     STARTCHAR j
     ENCODING 106
     SWIDTH 355 0
     DWIDTH 8 0
     BBX 9 22 -2 -6
     BITMAP
     0380
     0380
     0380
     0380
     0000
     0700
     0700
     0700
     0700
     0E00
     0E00
     0E00
     0E00
     0E00









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     1C00
     1C00
     1C00
     1C00
     3C00
     7800
     F000
     E000
     ENDCHAR
     STARTCHAR quoteright
     ENCODING 39
     SWIDTH 223 0
     DWIDTH 5 0
     BBX 4 6 2 12
     ATTRIBUTES 01C0
     BITMAP
     70
     70
     70
     60
     E0
     C0
     ENDCHAR
     ENDFONT