class TTFunk::TTFEncoder

Constants

OPTIMAL_TABLE_ORDER

Attributes

options[R]
original[R]
subset[R]

Public Class Methods

new(original, subset, options = {}) click to toggle source
# File lib/ttfunk/ttf_encoder.rb, line 12
def initialize(original, subset, options = {})
  @original = original
  @subset = subset
  @options = options
end

Public Instance Methods

encode() click to toggle source
# File lib/ttfunk/ttf_encoder.rb, line 18
def encode
  # https://www.microsoft.com/typography/otspec/otff.htm#offsetTable
  search_range = 2**Math.log2(tables.length).floor * 16
  entry_selector = Math.log2(2**Math.log2(tables.length).floor).to_i
  range_shift = tables.length * 16 - search_range
  range_shift = 0 if range_shift.negative?

  newfont = EncodedString.new

  newfont << [
    original.directory.scaler_type,
    tables.length,
    search_range,
    entry_selector,
    range_shift
  ].pack('Nn*')

  # Tables are supposed to be listed in ascending order whereas there is a
  # known optimal order for table data.
  tables.keys.sort.each do |tag|
    newfont << [tag, checksum(tables[tag])].pack('A4N')
    newfont << Placeholder.new(tag, length: 4)
    newfont << [tables[tag].length].pack('N')
  end

  optimal_table_order.each do |optimal_tag|
    next unless tables.include?(optimal_tag)

    newfont.resolve_placeholder(optimal_tag, [newfont.length].pack('N'))
    newfont << tables[optimal_tag]
    newfont.align!(4)
  end

  sum = checksum(newfont)
  adjustment = 0xB1B0AFBA - sum
  newfont.resolve_placeholder(:checksum, [adjustment].pack('N'))

  newfont.string
end

Private Instance Methods

align(data, width) click to toggle source
# File lib/ttfunk/ttf_encoder.rb, line 211
def align(data, width)
  if (data.length % width).positive?
    data + "\0" * (width - data.length % width)
  else
    data
  end
end
checksum(data) click to toggle source
# File lib/ttfunk/ttf_encoder.rb, line 203
def checksum(data)
  align(raw(data), 4).unpack('N*').sum & 0xFFFF_FFFF
end
cmap_table() click to toggle source

“mandatory” tables. Every font should (“should”) have these

# File lib/ttfunk/ttf_encoder.rb, line 68
def cmap_table
  @cmap_table ||= subset.new_cmap_table
end
cvt_table() click to toggle source
# File lib/ttfunk/ttf_encoder.rb, line 128
def cvt_table
  @cvt_table ||= TTFunk::Table::Simple.new(original, 'cvt ').raw
end
dsig_table() click to toggle source
# File lib/ttfunk/ttf_encoder.rb, line 163
def dsig_table
  @dsig_table ||= TTFunk::Table::Dsig.encode(
    original.digital_signature
  )
end
fpgm_table() click to toggle source
# File lib/ttfunk/ttf_encoder.rb, line 132
def fpgm_table
  @fpgm_table ||= TTFunk::Table::Simple.new(original, 'fpgm').raw
end
gasp_table() click to toggle source
# File lib/ttfunk/ttf_encoder.rb, line 140
def gasp_table
  @gasp_table ||= TTFunk::Table::Simple.new(original, 'gasp').raw
end
glyf_table() click to toggle source
# File lib/ttfunk/ttf_encoder.rb, line 72
def glyf_table
  @glyf_table ||= TTFunk::Table::Glyf.encode(
    glyphs, new_to_old_glyph, old_to_new_glyph
  )
end
glyphs() click to toggle source
# File lib/ttfunk/ttf_encoder.rb, line 191
def glyphs
  subset.glyphs
end
head_table() click to toggle source
# File lib/ttfunk/ttf_encoder.rb, line 114
def head_table
  @head_table ||= TTFunk::Table::Head.encode(
    original.header, loca_table, new_to_old_glyph
  )
end
hhea_table() click to toggle source
# File lib/ttfunk/ttf_encoder.rb, line 90
def hhea_table
  @hhea_table = TTFunk::Table::Hhea.encode(
    original.horizontal_header, hmtx_table, original, new_to_old_glyph
  )
end
hmtx_table() click to toggle source
# File lib/ttfunk/ttf_encoder.rb, line 84
def hmtx_table
  @hmtx_table ||= TTFunk::Table::Hmtx.encode(
    original.horizontal_metrics, new_to_old_glyph
  )
end
kern_table() click to toggle source
# File lib/ttfunk/ttf_encoder.rb, line 144
def kern_table
  # for PDFs, the kerning info is all included in the PDF as the text is
  # drawn. Thus, the PDF readers do not actually use the kerning info in
  # embedded fonts. If the library is used for something else, the
  # generated subfont may need a kerning table... in that case, you need
  # to opt into it.
  if options[:kerning]
    @kern_table ||= TTFunk::Table::Kern.encode(
      original.kerning, old_to_new_glyph
    )
  end
end
loca_table() click to toggle source
# File lib/ttfunk/ttf_encoder.rb, line 78
def loca_table
  @loca_table ||= TTFunk::Table::Loca.encode(
    glyf_table[:offsets]
  )
end
maxp_table() click to toggle source
# File lib/ttfunk/ttf_encoder.rb, line 96
def maxp_table
  @maxp_table ||= TTFunk::Table::Maxp.encode(
    original.maximum_profile, old_to_new_glyph
  )
end
name_table() click to toggle source
# File lib/ttfunk/ttf_encoder.rb, line 108
def name_table
  @name_table ||= TTFunk::Table::Name.encode(
    original.name, glyf_table.fetch(:table, '')
  )
end
new_to_old_glyph() click to toggle source
# File lib/ttfunk/ttf_encoder.rb, line 195
def new_to_old_glyph
  subset.new_to_old_glyph
end
old_to_new_glyph() click to toggle source
# File lib/ttfunk/ttf_encoder.rb, line 199
def old_to_new_glyph
  subset.old_to_new_glyph
end
optimal_table_order() click to toggle source
# File lib/ttfunk/ttf_encoder.rb, line 60
def optimal_table_order
  OPTIMAL_TABLE_ORDER +
    (tables.keys - ['DSIG'] - OPTIMAL_TABLE_ORDER) +
    ['DSIG']
end
os2_table() click to toggle source

“optional” tables. Fonts may omit these if they do not need them. Because they apply globally, we can simply copy them over, without modification, if they exist.

# File lib/ttfunk/ttf_encoder.rb, line 124
def os2_table
  @os2_table ||= TTFunk::Table::OS2.encode(original.os2, subset)
end
post_table() click to toggle source
# File lib/ttfunk/ttf_encoder.rb, line 102
def post_table
  @post_table ||= TTFunk::Table::Post.encode(
    original.postscript, new_to_old_glyph
  )
end
prep_table() click to toggle source
# File lib/ttfunk/ttf_encoder.rb, line 136
def prep_table
  @prep_table ||= TTFunk::Table::Simple.new(original, 'prep').raw
end
raw(data) click to toggle source
# File lib/ttfunk/ttf_encoder.rb, line 207
def raw(data)
  data.respond_to?(:unresolved_string) ? data.unresolved_string : data
end
tables() click to toggle source
# File lib/ttfunk/ttf_encoder.rb, line 169
def tables
  @tables ||= {
    'cmap' => cmap_table[:table],
    'glyf' => glyf_table[:table],
    'loca' => loca_table[:table],
    'kern' => kern_table,
    'hmtx' => hmtx_table[:table],
    'hhea' => hhea_table,
    'maxp' => maxp_table,
    'OS/2' => os2_table,
    'post' => post_table,
    'name' => name_table,
    'head' => head_table,
    'prep' => prep_table,
    'fpgm' => fpgm_table,
    'cvt ' => cvt_table,
    'VORG' => vorg_table,
    'DSIG' => dsig_table,
    'gasp' => gasp_table
  }.compact
end
vorg_table() click to toggle source
# File lib/ttfunk/ttf_encoder.rb, line 157
def vorg_table
  @vorg_table ||= TTFunk::Table::Vorg.encode(
    original.vertical_origins
  )
end