module TTFunk::Table::Cmap::Format12

Format 12: Segmented coverage.

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 12.

@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/format12.rb, line 30
def self.encode(charmap)
  next_id = 0
  glyph_map = { 0 => 0 }
  range_firstglyphs = []
  range_firstcodes = []
  range_lengths = []
  last_glyph = last_code = -999

  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]] }

      if code > last_code + 1 || glyph_map[charmap[code]] > last_glyph + 1
        range_firstcodes << code
        range_firstglyphs << glyph_map[charmap[code]]
        range_lengths << 1
      else
        range_lengths.push(range_lengths.pop) + 1
      end
      last_code = code
      last_glyph = glyph_map[charmap[code]]
    end

  subtable = [
    12, 0, 16 + (12 * range_lengths.size), 0, range_lengths.size,
  ].pack('nnNNN')
  range_lengths.each_with_index do |length, i|
    firstglyph = range_firstglyphs[i]
    firstcode = range_firstcodes[i]
    subtable << [
      firstcode, firstcode + length - 1, firstglyph,
    ].pack('NNN')
  end

  { 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/format12.rb, line 72
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/format12.rb, line 79
def supported?
  true
end

Private Instance Methods

parse_cmap!() click to toggle source
# File lib/ttfunk/table/cmap/format12.rb, line 85
def parse_cmap!
  fractional_version, @language, groupcount = read(14, 'nx4NN')
  if fractional_version != 0
    raise NotImplementedError,
      "cmap version 12.#{fractional_version} is not supported"
  end
  @code_map = {}
  (1..groupcount).each do
    startchar, endchar, startglyph = read(12, 'NNN')
    (0..(endchar - startchar)).each do |offset|
      @code_map[startchar + offset] = startglyph + offset
    end
  end
end