103 lines
3.3 KiB
Ruby
103 lines
3.3 KiB
Ruby
# frozen_string_literal: true
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module TTFunk
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class Table
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class Cmap
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# Format 12: Segmented coverage.
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#
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# This module conditionally extends {TTFunk::Table::Cmap::Subtable}.
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module Format12
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# Language.
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# @return [Integer]
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attr_reader :language
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# Code map.
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# @return [Hash{Integer => Integer}]
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attr_reader :code_map
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# Encode the encoding record to format 12.
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#
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# @param charmap [Hash{Integer => Integer}] a hash mapping character
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# codes to glyph IDs from the original font.
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# @return [Hash]
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# * `:charmap` (<tt>Hash{Integer => Hash}</tt>) keys are the characrers in
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# `charset`, values are hashes:
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# * `:old` (<tt>Integer</tt>) - glyph ID in the original font.
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# * `:new` (<tt>Integer</tt>) - glyph ID in the subset font.
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# that maps the characters in charmap to a
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# * `:subtable` (<tt>String</tt>) - serialized encoding record.
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# * `:max_glyph_id` (<tt>Integer</tt>) - maximum glyph ID in the new font.
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def self.encode(charmap)
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next_id = 0
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glyph_map = { 0 => 0 }
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range_firstglyphs = []
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range_firstcodes = []
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range_lengths = []
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last_glyph = last_code = -999
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new_map =
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charmap.keys.sort.each_with_object({}) do |code, map|
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glyph_map[charmap[code]] ||= next_id += 1
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map[code] = { old: charmap[code], new: glyph_map[charmap[code]] }
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if code > last_code + 1 || glyph_map[charmap[code]] > last_glyph + 1
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range_firstcodes << code
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range_firstglyphs << glyph_map[charmap[code]]
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range_lengths << 1
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else
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range_lengths.push(range_lengths.pop) + 1
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end
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last_code = code
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last_glyph = glyph_map[charmap[code]]
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end
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subtable = [
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12, 0, 16 + (12 * range_lengths.size), 0, range_lengths.size,
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].pack('nnNNN')
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range_lengths.each_with_index do |length, i|
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firstglyph = range_firstglyphs[i]
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firstcode = range_firstcodes[i]
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subtable << [
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firstcode, firstcode + length - 1, firstglyph,
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].pack('NNN')
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end
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{ charmap: new_map, subtable: subtable, max_glyph_id: next_id + 1 }
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end
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# Get glyph ID for character code.
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#
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# @param code [Integer] character code.
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# @return [Integer] glyph ID.
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def [](code)
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@code_map[code] || 0
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end
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# Is this encoding record format supported?
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#
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# @return [true]
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def supported?
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true
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end
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private
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def parse_cmap!
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fractional_version, @language, groupcount = read(14, 'nx4NN')
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if fractional_version != 0
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raise NotImplementedError,
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"cmap version 12.#{fractional_version} is not supported"
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end
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@code_map = {}
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(1..groupcount).each do
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startchar, endchar, startglyph = read(12, 'NNN')
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(0..(endchar - startchar)).each do |offset|
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@code_map[startchar + offset] = startglyph + offset
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end
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end
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end
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end
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end
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end
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end
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