PDF::API3::Compat::API2::Basic::TTF::Kern(3)

NAME
PDF::API3::Compat::API2::Basic::TTF::Kern - Kerning tables

DESCRIPTION
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.

INSTANCE VARIABLES
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

METHODS

  $t->read
Reads the whole kerning table into structures

  $t->out($fh)
Outputs the kerning tables to the given file

  $t->XML_element($context, $depth, $key, $value)
Handles outputting the kern hash into XML a little more tidily

BUGS

•   Only supports kerning table types 0 & 2.

•   No real support functions to do anything with the kerning tables yet.

AUTHOR
Martin Hosken Martin_Hosken@sil.org. See PDF::API3::Compat::API2::Basic::TTF::Font for copyright and licensing.