The Font Header Table

head - Font Header

This table gives global information about the font. The bounding box values should be computed using only glyphs that have contours. Glyphs with no contours should be ignored for the purposes of these calculations.

Type Name Description

Fixed Table version number 0x00010000 for version 1.0.

Fixed fontRevision Set by font manufacturer.

ULONG checkSumAdjustment To compute: set it to 0, sum the entire font as ULONG, then store 0xB1B0AFBA - sum.

ULONG magicNumber Set to 0x5F0F3CF5.

USHORT flags Bit 0 - baseline for font at y=0;

Bit 1 - left sidebearing at x=0;

Bit 2 - instructions may depend on point size;

Bit 3 - force ppem to integer values for all internal scaler math; may use fractional ppem sizes if this bit is clear;

Bit 4 - instructions may alter advance width (the advance widths might not scale linearly);

Bits 5-10 - defined by Apple;

Bit 11 - font compressed with Agfa MicroType Compression.

Note: All other bits must be zero.

USHORT unitsPerEm Valid range is from 16 to 16384

longDateTime created International date (8-byte field).

longDateTime modified International date (8-byte field).

FWord xMin For all glyph bounding boxes.

FWord yMin For all glyph bounding boxes.

FWord xMax For all glyph bounding boxes.

FWord yMax For all glyph bounding boxes.

USHORT macStyle Bit 0 bold (if set to 1); Bit 1 italic (if set to 1)
Bits 2-15 reserved (set to 0).

USHORT lowestRecPPEM Smallest readable size in pixels.

SHORT fontDirectionHint 0 Fully mixed directional glyphs;

1 Only strongly left to right;

2 Like 1 but also contains neutrals;

-1 Only strongly right to left;

-2 Like -1 but also contains neutrals.

SHORT indexToLocFormat 0 for short offsets, 1 for long.

SHORT glyphDataFormat 0 for current format.

Type	Name	Description
Fixed	Table version number	0x00010000 for version 1.0.
Fixed	fontRevision	Set by font manufacturer.
ULONG	checkSumAdjustment	To compute: set it to 0, sum the entire font as ULONG, then store 0xB1B0AFBA - sum.
ULONG	magicNumber	Set to 0x5F0F3CF5.
USHORT	flags	Bit 0 - baseline for font at y=0; Bit 1 - left sidebearing at x=0; Bit 2 - instructions may depend on point size; Bit 3 - force ppem to integer values for all internal scaler math; may use fractional ppem sizes if this bit is clear; Bit 4 - instructions may alter advance width (the advance widths might not scale linearly); Bits 5-10 - defined by Apple; Bit 11 - font compressed with Agfa MicroType Compression. Note: All other bits must be zero.
USHORT	unitsPerEm	Valid range is from 16 to 16384
longDateTime	created	International date (8-byte field).
longDateTime	modified	International date (8-byte field).
FWord	xMin	For all glyph bounding boxes.
FWord	yMin	For all glyph bounding boxes.
FWord	xMax	For all glyph bounding boxes.
FWord	yMax	For all glyph bounding boxes.
USHORT	macStyle	Bit 0 bold (if set to 1); Bit 1 italic (if set to 1) Bits 2-15 reserved (set to 0).
USHORT	lowestRecPPEM	Smallest readable size in pixels.
SHORT	fontDirectionHint	0 Fully mixed directional glyphs; 1 Only strongly left to right; 2 Like 1 but also contains neutrals; -1 Only strongly right to left; -2 Like -1 but also contains neutrals.
SHORT	indexToLocFormat	0 for short offsets, 1 for long.
SHORT	glyphDataFormat	0 for current format.

¹ A neutral character has no inherent directionality; it is not a character with zero (0) width. Spaces and punctuation are examples of neutral characters. Non-neutral characters are those with inherent directionality. For example, Roman letters (left-to-right) and Arabic letters(right-to-left) have directionality. In a "normal" Roman font where spaces and punctuation are present, the font direction hints should be set to two (2).

Note that macStyle bits must agree with the 'OS/2' table fsSelection bits. The fsSelection bits are used over the macStyle bits in Microsoft Windows. The PANOSE values and 'post' table values are ignored for determining bold or italic fonts.

The Date format used in this table follows the Macintosh convention of the number of seconds since 1904 (see Apple's Inside Macintosh series).