module TTFunk::Table::Cmap::Format06

Format 6: Trimmed table mapping.

This module conditionally extends {TTFunk::Table::Cmap::Subtable}.

Attributes

code_map[R]

Code map. @return [Hash{Integer => Integer}]

language[R]

Language. @return [Integer]

Public Class Methods

encode(charmap) click to toggle source

Encode the encoding record to format 6.

@param charmap [Hash{Integer => Integer}] a hash mapping character

codes to glyph IDs from the original font.

@return [Hash]

* `:charmap` (<tt>Hash{Integer => Hash}</tt>) keys are the characrers in
  `charset`, values are hashes:
  * `:old` (<tt>Integer</tt>) - glyph ID in the original font.
  * `:new` (<tt>Integer</tt>) - glyph ID in the subset font.
  that maps the characters in charmap to a
* `:subtable` (<tt>String</tt>) - serialized encoding record.
* `:max_glyph_id` (<tt>Integer</tt>) - maximum glyph ID in the new font.
# File lib/ttfunk/table/cmap/format06.rb, line 30
def self.encode(charmap)
  next_id = 0
  glyph_map = { 0 => 0 }

  sorted_chars = charmap.keys.sort
  low_char = sorted_chars.first
  high_char = sorted_chars.last
  entry_count = 1 + high_char - low_char
  glyph_indexes = Array.new(entry_count, 0)

  new_map =
    charmap.keys.sort.each_with_object({}) do |code, map|
      glyph_map[charmap[code]] ||= next_id += 1
      map[code] = { old: charmap[code], new: glyph_map[charmap[code]] }
      glyph_indexes[code - low_char] = glyph_map[charmap[code]]
    end

  subtable = [
    6, 10 + (entry_count * 2), 0, low_char, entry_count, *glyph_indexes,
  ].pack('n*')

  { charmap: new_map, subtable: subtable, max_glyph_id: next_id + 1 }
end

Public Instance Methods

[](code) click to toggle source

Get glyph ID for character code.

@param code [Integer] character code. @return [Integer] glyph ID.

# File lib/ttfunk/table/cmap/format06.rb, line 58
def [](code)
  @code_map[code] || 0
end
supported?() click to toggle source

Is this encoding record format supported?

@return [true]

# File lib/ttfunk/table/cmap/format06.rb, line 65
def supported?
  true
end

Private Instance Methods

parse_cmap!() click to toggle source
# File lib/ttfunk/table/cmap/format06.rb, line 71
def parse_cmap!
  @language, firstcode, entrycount = read(8, 'x2nnn')
  @code_map = {}
  (firstcode...(firstcode + entrycount)).each do |code|
    @code_map[code] = read(2, 'n').first & 0xFFFF
  end
end