Class: Prawn::Fonts::ToUnicodeCMap

Inherits:
Object
  • Object
show all
Defined in:
lib/prawn/fonts/to_unicode_cmap.rb

Overview

This class generates ToUnicode CMap for embedde TrueType/OpenType fonts. It’s a separate format and is somewhat complicated so it has its own place.

Instance Method Summary collapse

Constructor Details

#initialize(mapping, code_space_size = nil) ⇒ ToUnicodeCMap

mapping is expected to be a hash with keys being character codes (in broad sense, as used in the showing operation strings) and values being Unicode code points.



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# File 'lib/prawn/fonts/to_unicode_cmap.rb', line 14

def initialize(mapping, code_space_size = nil)
  @mapping = mapping
  @code_space_size = code_space_size
end

Instance Method Details

#generate ⇒ String

Generate CMap.

Returns:

  • (String) 


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# File 'lib/prawn/fonts/to_unicode_cmap.rb', line 22

def generate
  chunks = []

  # Header
  chunks << "    /CIDInit /ProcSet findresource begin\n    12 dict begin\n    begincmap\n    /CIDSystemInfo 3 dict dup begin\n      /Registry (Adobe) def\n      /Ordering (UCS) def\n      /Supplement 0 def\n    end def\n    /CMapName /Adobe-Identity-UCS def\n    /CMapType 2 def\n  HEADER\n\n  max_glyph_index = mapping.keys.max\n  # Range\n  code_space_size = (max_glyph_index.bit_length / 8.0).ceil\n\n  used_code_space_size = @code_space_size || code_space_size\n\n  # In CMap codespaces are not sequentional, they're ranges in\n  # a multi-dimentional space. Each byte is considered separately. So we\n  # have to maximally extend the lower bytes in order to allow for\n  # continuos mapping.\n  # We only keep the highest byte because usually it's lower than\n  # maximally allowed and we don't want to cover that unused space.\n  code_space_max = max_glyph_index | ('ff' * (code_space_size - 1)).to_i(16)\n\n  chunks << '1 begincodespacerange'\n  chunks << format(\"<%0\#{used_code_space_size * 2}X><%0\#{used_code_space_size * 2}X>\", 0, code_space_max)\n  chunks << 'endcodespacerange'\n\n  # Mapping\n  all_spans = mapping_spans(mapping.reject { |gid, cid| gid.zero? || (0xd800..0xdfff).cover?(cid) })\n\n  short_spans, long_spans = all_spans.partition { |span| span[0] == :short }\n\n  long_spans\n    .each_slice(100) do |spans|\n      chunks << \"\#{spans.length} beginbfrange\"\n\n      spans.each do |type, span|\n        # rubocop: disable Lint/FormatParameterMismatch # false positive\n        case type\n        when :fully_sorted\n          chunks << format(\n            \"<%0\#{code_space_size * 2}X><%0\#{code_space_size * 2}X><%s>\",\n            span.first[0],\n            span.last[0],\n            span.first[1].chr(::Encoding::UTF_16BE).unpack1('H*'),\n          )\n        when :index_sorted\n          chunks << format(\n            \"<%0\#{code_space_size * 2}X><%0\#{code_space_size * 2}X>[%s]\",\n            span.first[0],\n            span.last[0],\n            span.map { |_, cid| \"<\#{cid.chr(::Encoding::UTF_16BE).unpack1('H*')}>\" }.join(''),\n          )\n        end\n        # rubocop: enable Lint/FormatParameterMismatch\n      end\n\n      chunks << 'endbfrange'\n    end\n\n  short_spans\n    .map { |_type, slice| slice.flatten(1) }\n    .each_slice(100) do |mapping|\n      chunks << \"\#{mapping.length} beginbfchar\"\n      chunks.concat(\n        mapping.map { |(gid, cid)|\n          # rubocop: disable Lint/FormatParameterMismatch # false positive\n          format(\n            \"<%0\#{code_space_size * 2}X><%s>\",\n            gid,\n            cid.chr(::Encoding::UTF_16BE).unpack1('H*'),\n          )\n          # rubocop: enable Lint/FormatParameterMismatch\n        },\n      )\n      chunks << 'endbfchar'\n    end\n\n  # Footer\n  chunks << <<~FOOTER.chomp\n    endcmap\n    CMapName currentdict /CMap defineresource pop\n    end\n    end\n  FOOTER\n\n  chunks.join(\"\\n\")\nend\n".chomp