BDF header and properties

A BDF file holds one font: one typeface, at one size, in one orientation. It is plain text, so it has no offsets or binary fields; instead each line starts with an upper-case keyword followed by values separated by spaces. This page covers everything before the first glyph: the global keywords and the property block. The glyphs are on the Glyphs page.

Text rules

Only printable ASCII (0x20 to 0x7E) is used, plus the line endings.
A line ends with LF or with CR LF (the X Consortium’s 2.1 text allows either; Adobe’s documents describe CR LF).
Keywords are upper case and come first on the line; values are separated by spaces. In 2.1 numbers are decimal integers, which may be negative; 2.2 (section 3) also allows real numbers where a value is of type number.
Version 2.2 lifts the limit on line length: lines may be any length, and a string value may be up to 65,535 characters, the longest PostScript string (section 3 and the appendix).
COMMENT lines may appear anywhere between STARTFONT and ENDFONT, and are ignored.
Version 2.1 is the one adopted by the X Window System; version 2.2 (Adobe Technical Note #5005, 22 March 1993) adds metrics for a second writing direction (vertical text), font-wide metrics and the CONTENTVERSION keyword. Its appendix warns that a 2.2 file may not be readable by a 2.1 parser.

Global keywords

In this order:

Keyword	Values	Meaning
`STARTFONT`	version	Required, the first line: `2.1` or `2.2`.
`COMMENT`	text	Optional, anywhere; ignored.
`CONTENTVERSION`	integer	Version 2.2, optional. A number an installer can use to tell versions of the font data apart; it should change only when the bitmaps themselves are improved, not when the glyph set or encoding changes.
`FONT`	name	Required. The font’s name: the rest of the line, which may contain spaces. In X fonts an XLFD name; Adobe’s 2.2 text says it should match the PostScript `FontName` of the matching outline font (section 3.1).
`SIZE`	point size, x resolution, y resolution	Required. The size in points and the device resolution in dots per inch that the bitmaps were made for, e.g. `SIZE 24 75 75`.
`FONTBOUNDINGBOX`	width, height, x offset, y offset	Required. In pixels: the smallest box that holds every glyph when drawn at the origin, given by its size and the offset of its lower-left corner from the origin.
`METRICSSET`	0, 1 or 2	Version 2.2, optional. Which writing directions the glyphs have metrics for: 0 only direction 0 (horizontal, the default when absent), 1 only direction 1 (vertical), 2 both.
`STARTPROPERTIES`	count	Optional. Starts the property block of `count` lines.
`ENDPROPERTIES`	none	Ends the property block; required if it was started.
`CHARS`	count	Required. The number of glyphs that follow, each from `STARTCHAR` to `ENDCHAR`.
`ENDFONT`	none	Required, the last line.

Version 2.2 (section 3.1) also allows the per-glyph metric keywords SWIDTH, DWIDTH, SWIDTH1, DWIDTH1 and VVECTOR in this global section, before CHARS, to give one value for the whole font; a glyph that gives the same keyword overrides it. This saves space in ideographic fonts where most glyphs share metrics, but a file meant for 2.1 readers should not use it. With METRICSSET 1, SWIDTH and DWIDTH are optional. The keywords are described on the Glyphs page.

The property block

Each line between STARTPROPERTIES and ENDPROPERTIES is a property name and one value: an integer, or a string in double quotes, in which two double quotes stand for one. BDF itself defines no property names except three that every font should have:

Property	Type	Meaning
`FONT_ASCENT`	integer	Pixels above the baseline for spacing lines of text.
`FONT_DESCENT`	integer	Pixels below the baseline for spacing lines.
`DEFAULT_CHAR`	integer	The code of the glyph to show for a character the font lacks.

A compiler may reject a font without them, or make up values. When the X server compiled a BDF file these three became fields of the font rather than properties. All other names come from the X Logical Font Description conventions (XLFD), below, or are private names of the form _ORGANISATION_NAME.

The XLFD font name

An XLFD name is fourteen fields, each starting with a hyphen, for example -Adobe-Helvetica-Bold-R-Normal--24-240-75-75-P-65-ISO8859-1. The same fourteen values normally appear again as properties.

#	Field	Meaning
1	`FOUNDRY`	Who digitised the font or last changed it, e.g. `Adobe`.
2	`FAMILY_NAME`	Family name, e.g. `Helvetica`.
3	`WEIGHT_NAME`	The foundry’s weight name, e.g. `Medium`, `Bold`.
4	`SLANT`	`R` roman (upright), `I` italic, `O` oblique, `RI` reverse italic, `RO` reverse oblique, `OT` other. Italic and oblique lean clockwise, the reverse forms anticlockwise.
5	`SETWIDTH_NAME`	The foundry’s width name, e.g. `Normal`, `Condensed`.
6	`ADD_STYLE_NAME`	Any extra style words needed to make the name unique, e.g. `Sans`; often empty.
7	`PIXEL_SIZE`	Body size in pixels.
8	`POINT_SIZE`	Body size in decipoints (tenths of a point, 72.27 points to the inch).
9	`RESOLUTION_X`	Horizontal resolution in dots per inch.
10	`RESOLUTION_Y`	Vertical resolution in dots per inch.
11	`SPACING`	`P` proportional, `M` monospaced, `C` character cell (monospaced with no ink outside each cell).
12	`AVERAGE_WIDTH`	Mean glyph width in tenths of a pixel; negative for right-to-left fonts.
13	`CHARSET_REGISTRY`	Who registered the character set, e.g. `ISO8859`, `ISO10646`.
14	`CHARSET_ENCODING`	Which set of that registry, e.g. `1`; it says how `ENCODING` values map to characters.

In scalable fonts the size fields are 0. A 0 weight, slant or width, and bracketed matrices in the size fields, belong to scalable and polymorphic fonts rather than to BDF bitmaps.

Standard properties

The XLFD defines these further properties. Sizes are in pixels unless stated, and the types are those of the X protocol: ATOM is a string (quoted in BDF), INT32 a signed and CARD32 an unsigned integer.

Property	Type	Meaning
`MIN_SPACE`	INT32	Smallest word space to use (default ¾ of `NORM_SPACE`).
`NORM_SPACE`	INT32	Normal word space (default the width of the space glyph).
`MAX_SPACE`	INT32	Largest word space (default 1½ × `NORM_SPACE`).
`END_SPACE`	INT32	Space after a sentence (default `NORM_SPACE`).
`AVG_CAPITAL_WIDTH`	INT32	Mean width of capitals, tenths of a pixel.
`AVG_LOWERCASE_WIDTH`	INT32	Mean width of lower-case letters, tenths of a pixel.
`QUAD_WIDTH`	INT32	Width of an em space. Deprecated.
`FIGURE_WIDTH`	INT32	Width of the figures and dollar sign when they are all equal.
`SUPERSCRIPT_X`, `SUPERSCRIPT_Y`	INT32	Offset from the current point to a made-up superscript (y upwards).
`SUBSCRIPT_X`, `SUBSCRIPT_Y`	INT32	Offset to a made-up subscript (y downwards).
`SUPERSCRIPT_SIZE`, `SUBSCRIPT_SIZE`	INT32	Body size for those (default 0.6 × `PIXEL_SIZE`).
`SMALL_CAP_SIZE`	INT32	Body size for made-up small capitals.
`UNDERLINE_POSITION`	INT32	From the baseline to the top of the underline.
`UNDERLINE_THICKNESS`	INT32	Thickness of the underline.
`STRIKEOUT_ASCENT`, `STRIKEOUT_DESCENT`	INT32	Top and bottom of a box drawn over text, above and below the baseline.
`ITALIC_ANGLE`	INT32	Slant angle in 1/64 degree, anticlockwise from the 3 o’clock direction (upright is 90 × 64).
`CAP_HEIGHT`	INT32	Height of capitals.
`X_HEIGHT`	INT32	Height of lower-case letters such as x.
`RELATIVE_SETWIDTH`	CARD32	Width class: 0 undefined, 10 ultra-condensed to 90 ultra-expanded, 50 normal.
`RELATIVE_WEIGHT`	CARD32	Weight class: 0 undefined, 10 ultra-light to 90 ultra-bold, 50 medium.
`WEIGHT`	CARD32	Measured weight 0 to 1000: capital stem width × 1000 ÷ `CAP_HEIGHT`.
`RESOLUTION`	CARD32	Resolution in hundredths of a pixel per point. Deprecated.
`DESTINATION`	CARD32	0 made to match printed output, 1 made for legibility on screen.
`FONT`	ATOM	The full XLFD name.
`FACE_NAME`	ATOM	Full typeface name without size, e.g. “Helvetica Bold”.
`FULL_NAME`	ATOM	The same as `FACE_NAME`. Deprecated.
`COPYRIGHT`	ATOM	Copyright of the font data.
`NOTICE`	ATOM	Copyright of the design, or trademark notice for the name.
`FONT_TYPE`	ATOM	Where the font came from: `Bitmap`, `Prebuilt`, `Type 1`, `TrueType`, `Speedo`, `F3` or another registered name.
`FONT_VERSION`	ATOM	The font’s version.
`RASTERIZER_NAME`, `RASTERIZER_VERSION`	ATOM	The software that rendered a scaled font, and its version.
`RAW_ASCENT`, `RAW_DESCENT`, other `RAW_*`	INT32	For transformed fonts: the same metrics in units of 1/1000 of the pixel size.
`AXIS_NAMES`, `AXIS_LIMITS`, `AXIS_TYPES`	ATOM, integers, ATOM	Axes of polymorphic (variable) fonts: names, minimum and maximum of each, registered types.

Any of the fourteen name fields can also appear as a property of the same name: FOUNDRY, FAMILY_NAME (the BDF 2.1 sample writes FAMILY), WEIGHT_NAME, SLANT, SETWIDTH_NAME, ADD_STYLE_NAME, PIXEL_SIZE, POINT_SIZE, RESOLUTION_X, RESOLUTION_Y, SPACING, AVERAGE_WIDTH, CHARSET_REGISTRY, CHARSET_ENCODING.

Example

The start of the sample font in the BDF 2.1 specification, Adobe Helvetica Bold at 24 pixels:

STARTFONT 2.1
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

Every glyph fits in a box 9 pixels wide and 24 high whose lower-left corner is 2 pixels left of and 6 pixels below the origin. Lines of text are spaced 21 + 7 = 28 pixels apart. The two glyphs that follow are decoded on the Glyphs page.