82 lines
2.5 KiB
Ruby
82 lines
2.5 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 6: Trimmed table mapping.
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#
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# This module conditionally extends {TTFunk::Table::Cmap::Subtable}.
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module Format06
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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 6.
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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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sorted_chars = charmap.keys.sort
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low_char = sorted_chars.first
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high_char = sorted_chars.last
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entry_count = 1 + high_char - low_char
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glyph_indexes = Array.new(entry_count, 0)
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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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glyph_indexes[code - low_char] = glyph_map[charmap[code]]
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end
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subtable = [
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6, 10 + (entry_count * 2), 0, low_char, entry_count, *glyph_indexes,
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].pack('n*')
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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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@language, firstcode, entrycount = read(8, 'x2nnn')
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@code_map = {}
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(firstcode...(firstcode + entrycount)).each do |code|
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@code_map[code] = read(2, 'n').first & 0xFFFF
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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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