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' table.

The 'ankr' table starts with a header:

The 'ankr' table 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:

The 'ankr' table header
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.