The 'ankr' table
Introduction
The anchor point table (tag name: 'ankr') provides a way to define anchor points—points within the coordinate space of a given glyph independent of the control points used to render the glyph. Anchor points are used in conjunction with the 'kerx'.
The 'ankr' table starts with a header:
| Type | Name | Description |
|---|---|---|
| UInt16 | version | Version number (set to zero) |
| UInt16 | flags | Flags (currently unused; set to zero) |
| UInt32 | lookupTableOffset | Offset to the table's lookup table; currently this is always 0x0000000C |
| UInt32 | glyphDataTableOffset | Offset to the glyph data table |
The lookup table is a standard AAT lookup table. Values are two-byte offsets from the beginning of the glyph data table to the data for the given glyph. Because 0 is a valid value for such an offset, glyphs without anchor points must not be included in the lookup table.
The glyph data table is a series of glyph data entry, one for each glyph with anchor points. Glyph data entries are structured as follows:
| Type | Name | Description |
|---|---|---|
| UInt32 | numPoints | Number of anchor points for this glyph |
| UInt32[] | anchorPoints | Individual anchor points. Each anchor point is a two-byte signed x-coordinate followed by a two-byte signed y-coordinate |
Availability
The 'ankr' table is supported on OS X 10.9 (Mavericks) and later, and on iOS version 7.0 and later.