class Prawn::Font::TTF

@private

Constants

UNICODE_CMAP_TEMPLATE

Attributes

subsets[R]
ttf[R]

Public Class Methods

new(document, name, options={}) click to toggle source
Calls superclass method
# File lib/prawn/font/ttf.rb, line 23
def initialize(document, name, options={})
  super

  @ttf              = read_ttf_file
  @subsets          = TTFunk::SubsetCollection.new(@ttf)

  @attributes       = {}
  @bounding_boxes   = {}
  @char_widths      = {}
  @has_kerning_data = @ttf.kerning.exists? && @ttf.kerning.tables.any?

  @ascender         = Integer(@ttf.ascent * scale_factor)
  @descender        = Integer(@ttf.descent * scale_factor)
  @line_gap         = Integer(@ttf.line_gap * scale_factor)
end

Public Instance Methods

basename() click to toggle source
# File lib/prawn/font/ttf.rb, line 107
def basename
  @basename ||= @ttf.name.postscript_name
end
bbox() click to toggle source

The font bbox, as an array of integers

# File lib/prawn/font/ttf.rb, line 59
def bbox
  @bbox ||= @ttf.bbox.map { |i| Integer(i * scale_factor) }
end
cap_height() click to toggle source
# File lib/prawn/font/ttf.rb, line 127
def cap_height
  @cap_height ||= begin
    height = @ttf.os2.exists? && @ttf.os2.cap_height || 0
    height == 0 ? @ascender : height
  end
end
character_count(str) click to toggle source

Returns the number of characters in str (a UTF-8-encoded string).

# File lib/prawn/font/ttf.rb, line 186
def character_count(str)
  str.length
end
encode_text(text,options={}) click to toggle source

Perform any changes to the string that need to happen before it is rendered to the canvas. Returns an array of subset “chunks”, where the even-numbered indices are the font subset number, and the following entry element is either a string or an array (for kerned text).

The text parameter must be UTF8-encoded.

# File lib/prawn/font/ttf.rb, line 76
def encode_text(text,options={})
  text = text.chomp

  if options[:kerning]
    last_subset = nil
    kern(text).inject([]) do |result, element|
      if element.is_a?(Numeric)
        result.last[1] = [result.last[1]] unless result.last[1].is_a?(Array)
        result.last[1] << element
        result
      else
        encoded = @subsets.encode(element)

        if encoded.first[0] == last_subset
          result.last[1] << encoded.first[1]
          encoded.shift
        end

        if encoded.any?
          last_subset = encoded.last[0]
          result + encoded
        else
          result
        end
      end
    end
  else
    @subsets.encode(text.unpack("U*"))
  end
end
family_class() click to toggle source
# File lib/prawn/font/ttf.rb, line 140
def family_class
  @family_class ||= (@ttf.os2.exists? && @ttf.os2.family_class || 0) >> 8
end
glyph_present?(char) click to toggle source
# File lib/prawn/font/ttf.rb, line 179
def glyph_present?(char)
  code = char.codepoints.first
  cmap[code] > 0
end
has_kerning_data?() click to toggle source

Returns true if the font has kerning data, false otherwise

# File lib/prawn/font/ttf.rb, line 64
def has_kerning_data?
  @has_kerning_data
end
italic_angle() click to toggle source
# File lib/prawn/font/ttf.rb, line 116
def italic_angle
  @italic_angle ||= if @ttf.postscript.exists?
    raw = @ttf.postscript.italic_angle
    hi, low = raw >> 16, raw & 0xFF
    hi = -((hi ^ 0xFFFF) + 1) if hi & 0x8000 != 0
    "#{hi}.#{low}".to_f
  else
    0
  end
end
normalize_encoding(text) click to toggle source
# File lib/prawn/font/ttf.rb, line 163
def normalize_encoding(text)
  begin
    text.encode(::Encoding::UTF_8)
  rescue => e
    puts e
    raise Prawn::Errors::IncompatibleStringEncoding, "Encoding " +
      "#{text.encoding} can not be transparently converted to UTF-8. " +
      "Please ensure the encoding of the string you are attempting " +
      "to use is set correctly"
  end
end
pdf_flags() click to toggle source
# File lib/prawn/font/ttf.rb, line 152
def pdf_flags
  @flags ||= begin
    flags = 0
    flags |= 0x0001 if @ttf.postscript.fixed_pitch?
    flags |= 0x0002 if serif?
    flags |= 0x0008 if script?
    flags |= 0x0040 if italic_angle != 0
    flags |= 0x0004 # assume the font contains at least some non-latin characters
  end
end
script?() click to toggle source
# File lib/prawn/font/ttf.rb, line 148
def script?
  @script ||= family_class == 10
end
serif?() click to toggle source
# File lib/prawn/font/ttf.rb, line 144
def serif?
  @serif ||= [1,2,3,4,5,7].include?(family_class)
end
stemV() click to toggle source

not sure how to compute this for true-type fonts…

# File lib/prawn/font/ttf.rb, line 112
def stemV
  0
end
to_utf8(text) click to toggle source
# File lib/prawn/font/ttf.rb, line 175
def to_utf8(text)
  text.encode("UTF-8")
end
unicode?() click to toggle source
# File lib/prawn/font/ttf.rb, line 19
def unicode?
  true
end
x_height() click to toggle source
# File lib/prawn/font/ttf.rb, line 134
def x_height
  # FIXME: seems like if os2 table doesn't exist, we could
  # just find the height of the lower-case 'x' glyph?
  @ttf.os2.exists? && @ttf.os2.x_height || 0
end

Private Instance Methods

character_width_by_code(code) click to toggle source
# File lib/prawn/font/ttf.rb, line 231
def character_width_by_code(code)
  return 0 unless cmap[code]

  # Some TTF fonts have nonzero widths for \n (UTF-8 / ASCII code: 10).
  # Patch around this as we'll never be drawing a newline with a width.
  return 0.0 if code == 10

  @char_widths[code] ||= Integer(hmtx.widths[cmap[code]] * scale_factor)
end
cid_to_gid_map() click to toggle source
# File lib/prawn/font/ttf.rb, line 222
def cid_to_gid_map
  max = cmap.code_map.keys.max
  (0..max).map { |cid| cmap[cid] }.pack("n*")
end
cmap() click to toggle source
# File lib/prawn/font/ttf.rb, line 192
def cmap
  @cmap ||= @ttf.cmap.unicode.first or raise("no unicode cmap for font")
end
embed(reference, subset) click to toggle source
# File lib/prawn/font/ttf.rb, line 256
def embed(reference, subset)
  font_content = @subsets[subset].encode

  # FIXME: we need postscript_name and glyph widths from the font
  # subset. Perhaps this could be done by querying the subset,
  # rather than by parsing the font that the subset produces?
  font = TTFunk::File.new(font_content)

  # empirically, it looks like Adobe Reader will not display fonts
  # if their font name is more than 33 bytes long. Strange. But true.
  basename = font.name.postscript_name[0, 33].gsub("\0","")

  raise "Can't detect a postscript name for #{file}" if basename.nil?

  fontfile = @document.ref!(:Length1 => font_content.size)
  fontfile.stream << font_content
  fontfile.stream.compress!

  descriptor = @document.ref!(:Type        => :FontDescriptor,
                             :FontName    => basename.to_sym,
                             :FontFile2   => fontfile,
                             :FontBBox    => bbox,
                             :Flags       => pdf_flags,
                             :StemV       => stemV,
                             :ItalicAngle => italic_angle,
                             :Ascent      => @ascender,
                             :Descent     => @descender,
                             :CapHeight   => cap_height,
                             :XHeight     => x_height)

  hmtx = font.horizontal_metrics
  widths = font.cmap.tables.first.code_map.map { |gid|
    Integer(hmtx.widths[gid] * scale_factor) }[32..-1]

  # It would be nice to have Encoding set for the macroman subsets,
  # and only do a ToUnicode cmap for non-encoded unicode subsets.
  # However, apparently Adobe Reader won't render MacRoman encoded
  # subsets if original font contains unicode characters. (It has to
  # be some flag or something that ttfunk is simply copying over...
  # but I can't figure out which flag that is.)
  #
  # For now, it's simplest to just create a unicode cmap for every font.
  # It offends my inner purist, but it'll do.

  map = @subsets[subset].to_unicode_map

  ranges = [[]]
  map.keys.sort.inject("") do |s, code|
    ranges << [] if ranges.last.length >= 100
    unicode = map[code]
    ranges.last << "<%02x><%04x>" % [code, unicode]
  end

  range_blocks = ranges.inject("") do |s, list|
    s << "%d beginbfchar\n%s\nendbfchar\n" % [list.length, list.join("\n")]
  end

  to_unicode_cmap = UNICODE_CMAP_TEMPLATE % range_blocks.strip

  cmap = @document.ref!({})
  cmap << to_unicode_cmap
  cmap.stream.compress!

  reference.data.update(:Subtype => :TrueType,
                        :BaseFont => basename.to_sym,
                        :FontDescriptor => descriptor,
                        :FirstChar => 32,
                        :LastChar => 255,
                        :Widths => @document.ref!(widths),
                        :ToUnicode => cmap)
end
hmtx() click to toggle source
# File lib/prawn/font/ttf.rb, line 227
def hmtx
  @hmtx ||= @ttf.horizontal_metrics
end
kern(string) click to toggle source

string must be UTF8-encoded.

Returns an array. If an element is a numeric, it represents the kern amount to inject at that position. Otherwise, the element is an array of UTF-16 characters.

# File lib/prawn/font/ttf.rb, line 201
def kern(string)
  a = []

  string.each_codepoint do |r|
    if a.empty?
      a << [r]
    elsif (kern = kern_pairs_table[[cmap[a.last.last], cmap[r]]])
      kern *= scale_factor
      a << -kern << [r]
    else
      a.last << r
    end
  end

  a
end
kern_pairs_table() click to toggle source
# File lib/prawn/font/ttf.rb, line 218
def kern_pairs_table
  @kerning_data ||= has_kerning_data? ? @ttf.kerning.tables.first.pairs : {}
end
read_ttf_file() click to toggle source
# File lib/prawn/font/ttf.rb, line 349
def read_ttf_file
  TTFunk::File.open(@name)
end
register(subset) click to toggle source
# File lib/prawn/font/ttf.rb, line 245
def register(subset)
  temp_name = @ttf.name.postscript_name.gsub("\0","").to_sym
  ref = @document.ref!(:Type => :Font, :BaseFont => temp_name)

  # Embed the font metrics in the document after everything has been
  # drawn, just before the document is emitted.
  @document.renderer.before_render { |doc| embed(ref, subset) }

  ref
end
scale_factor() click to toggle source
# File lib/prawn/font/ttf.rb, line 241
def scale_factor
  @scale ||= 1000.0 / @ttf.header.units_per_em
end