Class: TTFunk::Table::Cff::Encoding

Inherits:
SubTable
  • Object
show all
Includes:
Enumerable
Defined in:
lib/ttfunk/table/cff/encoding.rb

Overview

CFF Encoding.

Constant Summary collapse

STANDARD_ENCODING_ID =

Predefined Standard Encoding ID.

0
EXPERT_ENCODING_ID =

Predefined Expert Encoding ID.

1
DEFAULT_ENCODING_ID =

Default encoding ID.

STANDARD_ENCODING_ID

Instance Attribute Summary collapse

Attributes inherited from SubTable

#file, #length, #table_offset

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from SubTable

#eot?, #read

Constructor Details

#initialize(top_dict, file, offset = nil, length = nil) ⇒ Encoding #initialize(top_dict, file, charset_id) ⇒ Encoding

Returns a new instance of Encoding.

Overloads:

  • #initialize(top_dict, file, offset = nil, length = nil) ⇒ Encoding

    Parameters:

    • top_dict (TTFunk::Table:Cff::TopDict)
    • file (TTFunk::File)
    • offset (Integer) (defaults to: nil)
    • length (Integer) (defaults to: nil)
  • #initialize(top_dict, file, charset_id) ⇒ Encoding

    Parameters:

    • top_dict (TTFunk::Table:Cff::TopDict)
    • file (TTFunk::File)
    • encoding_id (Integer) —

      0, 1, or 2



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# File 'lib/ttfunk/table/cff/encoding.rb', line 59

def initialize(top_dict, file, offset_or_id = nil, length = nil)
  @top_dict = top_dict
  @offset_or_id = offset_or_id || DEFAULT_ENCODING_ID

  if offset
    super(file, offset, length)
    @supplemental = format >> 7 == 1
  else
    @items_count = self.class.codes_for_encoding_id(offset_or_id).size
    @supplemental = false
  end
end

Instance Attribute Details

#format ⇒ Integer (readonly)

Encodign format.

Returns:

  • (Integer) 


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# File 'lib/ttfunk/table/cff/encoding.rb', line 40

def format
  @format
end

#items_count ⇒ Integer (readonly)

Number of encoded items.

Returns:

  • (Integer) 


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# File 'lib/ttfunk/table/cff/encoding.rb', line 44

def items_count
  @items_count
end

#offset_or_id ⇒ Integer (readonly)

Offset or encoding ID.

Returns:

  • (Integer) 


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# File 'lib/ttfunk/table/cff/encoding.rb', line 48

def offset_or_id
  @offset_or_id
end

#top_dict ⇒ TTFunk::Table::Cff::TopDict (readonly)

Top dict.

Returns:



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# File 'lib/ttfunk/table/cff/encoding.rb', line 36

def top_dict
  @top_dict
end

Class Method Details

.codes_for_encoding_id(encoding_id) ⇒ TTFunk::OneBasedArray<Integer>

Get predefined encoding by ID.

Parameters:

  • encoding_id (Integer)

Returns:



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# File 'lib/ttfunk/table/cff/encoding.rb', line 24

def codes_for_encoding_id(encoding_id)
  case encoding_id
  when STANDARD_ENCODING_ID
    Encodings::STANDARD
  when EXPERT_ENCODING_ID
    Encodings::EXPERT
  end
end

Instance Method Details

#[](glyph_id) ⇒ Integer?

Get character code for glyph index.

Parameters:

  • glyph_id (Integer)

Returns:

  • (Integer, nil) 


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# File 'lib/ttfunk/table/cff/encoding.rb', line 90

def [](glyph_id)
  return 0 if glyph_id.zero?
  return code_for(glyph_id) if offset

  self.class.codes_for_encoding_id(offset_or_id)[glyph_id]
end

#each {|code| ... } ⇒ void #each ⇒ Enumerator

Iterate over character codes.

Overloads:

  • #each {|code| ... } ⇒ void

    This method returns an undefined value.

    Yield Parameters:

    • code (Integer)
  • #each ⇒ Enumerator

    Returns:

    • (Enumerator) 


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# File 'lib/ttfunk/table/cff/encoding.rb', line 79

def each
  return to_enum(__method__) unless block_given?

  # +1 adjusts for the implicit .notdef glyph
  (items_count + 1).times { |i| yield(self[i]) }
end

#encode(charmap) ⇒ String

Encode encoding.

Parameters:

  • charmap (Hash{Integer => Hash}) —

    keys are the charac codes, values are hashes:

    • ‘:old` (Integer) - glyph ID in the original font.

    • ‘:new` (Integer) - glyph ID in the subset font.

Returns:

  • (String) 


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# File 'lib/ttfunk/table/cff/encoding.rb', line 120

def encode(charmap)
  # Any subset encoding is all but guaranteed to be different from the
  # standard encoding so we don't even attempt to see if it matches. We
  # assume it's different and just encode it anew.

  return encode_supplemental(charmap) if supplemental?

  codes =
    charmap
      .reject { |_code, mapping| mapping[:new].zero? }
      .sort_by { |_code, mapping| mapping[:new] }
      .map { |(code, _m)| code }

  ranges = TTFunk::BinUtils.rangify(codes)

  # calculate whether storing the charset as a series of ranges is
  # more efficient (i.e. takes up less space) vs storing it as an
  # array of SID values
  total_range_size = (2 * ranges.size) +
    (element_width(:range_format) * ranges.size)

  total_array_size = codes.size * element_width(:array_format)

  if total_array_size <= total_range_size
    ([format_int(:array_format), codes.size] + codes).pack('C*')
  else
    element_fmt = element_format(:range_format)
    result = [format_int(:range_format), ranges.size].pack('CC')
    ranges.each { |range| result << range.pack(element_fmt) }
    result
  end
end

#offset ⇒ Integer?

Encoding offset in the file.

Returns:

  • (Integer, nil) 


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# File 'lib/ttfunk/table/cff/encoding.rb', line 100

def offset
  # Numbers from 0..1 mean encoding IDs instead of offsets. IDs are
  # pre-defined, generic encodings that define the characters present
  # in the font.
  #
  # In the case of an offset, add the CFF table's offset since the
  # charset offset is relative to the start of the CFF table. Otherwise
  # return nil (no offset).
  if offset_or_id > 1
    offset_or_id + top_dict.cff_offset
  end
end

#supplemental? ⇒ Boolean

Is this a supplemental encoding?

Returns:

  • (Boolean) 


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# File 'lib/ttfunk/table/cff/encoding.rb', line 156

def supplemental?
  # high-order bit set to 1 indicates supplemental encoding
  @supplemental
end