The 'bhed' table

General table information

The 'bhed' table contains global information about a bitmap font. It records such facts as the font version number, the creation and modification dates, revision number and basic typographic data that applies to the font as a whole. This includes a specification of the font bounding box, the direction in which the font's glyphs are most likely to be written and other information about the placement of glyphs in the em square. The checksum is used to verify the integrity of the data in the font. It can also be used to distinguish between two similar fonts.

The 'bhed' table is byte-for-byte identical with the 'head' (font header) table. Mac OS uses the presence of a 'bhed' table as a flag that a font doesn't have any glyph outlines but only embedded bitmaps. For more information on the fields in a 'bhed' table and their values, see the documentation for the 'head' (font header) table.

Mac OS-specific information

This table is used in the Mac OS to signal the presence of a bitmap-only font. It is required if a font has no outlines. If a font does have outlines, then there should be no 'bhed' table.

Newton-specific information

Newton fonts are bitmap-only, but the Newton OS does not use the 'bhed' table. Fonts for the Newton should include a standard 'head' table instead.

When porting a font from the Newton to the Mac OS, the 'head' table should be replaced by an equivalent 'bhed' table. The font will then work properly on the Mac OS.

Dependencies

If a 'bhed' table is present in a font, the font must also have 'bdat' and 'bloc' tables. The font must have no 'head' or 'glyf' tables.

Field dependencies between the 'bhed' table's fields and other tables are described in the documentation for the 'head' (font header) table.

Fonts with bitmaps may require external fbit ("marukan") files to work properly on East Asian systems. Fbit files can be generated with TrueEdit.

Tools

No tools are currently configured to edit the 'bhed' table. Hexadecimal edits are possible using TrueEdit.

Change Log

6 August 1998

Created document.

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