Font::TTF::Kern  Kerning tables

Font::TTF::Kern  Kerning tables
Kerning tables are held as an ordered collection of subtables each giving
incremental information regarding the kerning of various pairs of glyphs.
The basic structure of the kerning data structure is:
$kern = $f>{'kern'}{'tables'}[$tnum]{'kerns'}{$leftnum}{$rightnum};
Due to the possible complexity of some kerning tables the above information
is insufficient. Reference also needs to be made to the type of the table and
the coverage field.
The instance variables for a kerning table are relatively straightforward.
 Version

Version number of the kerning table
 Num

Number of subtables in the kerning table
 tables

Array of subtables in the kerning table
Each subtable has a number of instance variables.
 kern

A two level hash array containing kerning values. The indexing is left
value and then right value. In the case of type 2 tables, the indexing
is via left class and right class. It may seem using hashes is strange,
but most tables are not type 2 and this method saves empty array values.
 type

Stores the table type. Only type 0 and type 2 tables are specified for
TrueType so far.
 coverage

A bit field of coverage information regarding the kerning value. See the
TrueType specification for details.
 Version

Contains the version number of the table.
 Num

Number of kerning pairs in this type 0 table.
 left

An array indexed by glyph  left_first which returns a class number for
the glyph in type 2 tables.
 right

An array indexed by glyph  right_first which returns a class number for
the glyph in type 2 tables.
 left_first

the glyph number of the first element in the left array for type 2 tables.
 right_first

the glyph number of the first element in the right array for type 2 tables.
 num_left

Number of left classes
 num_right

Number of right classes
Reads the whole kerning table into structures
Outputs the kerning tables to the given file
Handles outputting the kern hash into XML a little more tidily

Only supports kerning table types 0 & 2.

No real support functions to do anything with the kerning tables yet.
Martin Hosken Martin_Hosken@sil.org. See the Font::TTF::Font manpage for copyright and
licensing.
Font::TTF::Kern  Kerning tables
