Class: TTFunk::Subset::Base

Inherits:
Object
  • Object
show all
Defined in:
lib/ttfunk/subset/base.rb

Direct Known Subclasses

MacRoman, Unicode, Unicode8Bit, Windows1252

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(original) ⇒ Base

Returns a new instance of Base.



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# File 'lib/ttfunk/subset/base.rb', line 18

def initialize(original)
  @original = original
end

Instance Attribute Details

#original ⇒ Object (readonly)

Returns the value of attribute original.



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# File 'lib/ttfunk/subset/base.rb', line 16

def original
  @original
end

Instance Method Details

#encode(options = {}) ⇒ Object 



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# File 'lib/ttfunk/subset/base.rb', line 30

def encode(options={})
  cmap_table = new_cmap_table(options)
  glyphs = collect_glyphs(original_glyph_ids)

  old2new_glyph = cmap_table[:charmap].inject({ 0 => 0 }) { |map, (_, ids)| map[ids[:old]] = ids[:new]; map }
  next_glyph_id = cmap_table[:max_glyph_id]

  glyphs.keys.each do |old_id|
    unless old2new_glyph.key?(old_id)
      old2new_glyph[old_id] = next_glyph_id
      next_glyph_id += 1
    end
  end

  new2old_glyph = old2new_glyph.invert

  # "mandatory" tables. Every font should ("should") have these, including
  # the cmap table (encoded above).
  glyf_table = TTFunk::Table::Glyf.encode(glyphs, new2old_glyph, old2new_glyph)
  loca_table = TTFunk::Table::Loca.encode(glyf_table[:offsets])
  hmtx_table = TTFunk::Table::Hmtx.encode(original.horizontal_metrics, new2old_glyph)
  hhea_table = TTFunk::Table::Hhea.encode(original.horizontal_header, hmtx_table)
  maxp_table = TTFunk::Table::Maxp.encode(original.maximum_profile, old2new_glyph)
  post_table = TTFunk::Table::Post.encode(original.postscript, new2old_glyph)
  name_table = TTFunk::Table::Name.encode(original.name)
  head_table = TTFunk::Table::Head.encode(original.header, loca_table)

  # "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.
  os2_table  = original.os2.raw
  cvt_table  = TTFunk::Table::Simple.new(original, "cvt ").raw
  fpgm_table = TTFunk::Table::Simple.new(original, "fpgm").raw
  prep_table = TTFunk::Table::Simple.new(original, "prep").raw

  # for PDF's, 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, old2new_glyph)
  end

  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 }

  tables.delete_if { |tag, table| table.nil? }

  search_range = (Math.log(tables.length) / Math.log(2)).to_i * 16
  entry_selector = (Math.log(search_range) / Math.log(2)).to_i
  range_shift = tables.length * 16 - search_range

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

  directory_size = tables.length * 16
  offset = newfont.length + directory_size

  table_data = ""
  head_offset = nil
  tables.each do |tag, data|
    newfont << [tag, checksum(data), offset, data.length].pack("A4N*")
    table_data << data
    head_offset = offset if tag == 'head'
    offset += data.length
    while offset % 4 != 0
      offset += 1
      table_data << "\0"
    end
  end

  newfont << table_data
  sum = checksum(newfont)
  adjustment = 0xB1B0AFBA - sum
  newfont[head_offset+8,4] = [adjustment].pack("N")

  return newfont
end

#to_unicode_map ⇒ Object 



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# File 'lib/ttfunk/subset/base.rb', line 26

def to_unicode_map
  {}
end

#unicode? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/ttfunk/subset/base.rb', line 22

def unicode?
  false
end