100 lines
2.7 KiB
Ruby
100 lines
2.7 KiB
Ruby
# frozen_string_literal: true
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require 'set'
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require_relative 'base'
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module TTFunk
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module Subset
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# An 8-bit Unicode-based subset. It can include any Unicode character but
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# limits number of characters so that the could be encoded by a single byte.
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class Unicode8Bit < Base
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# @param original [TTFunk::File]
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def initialize(original)
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super
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@subset = { 0x20 => 0x20 }
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@unicodes = { 0x20 => 0x20 }
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@next = 0x21 # apparently, PDF's don't like to use chars between 0-31
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end
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# Is this a Unicode-based subset?
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#
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# @return [true]
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def unicode?
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true
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end
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# Get a mapping from this subset to Unicode.
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#
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# @return [Hash{Integer => Integer}]
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def to_unicode_map
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@subset.dup
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end
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# Add a character to subset.
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#
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# @param character [Integer] Unicode codepoint
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# @return [void]
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def use(character)
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unless @unicodes.key?(character)
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@subset[@next] = character
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@unicodes[character] = @next
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@next += 1
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end
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end
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# Can this subset include the character?
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#
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# @param character [Integer] Unicode codepoint
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# @return [Boolean]
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def covers?(character)
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@unicodes.key?(character) || @next < 256
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end
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# Does this subset actually has the character?
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#
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# @param character [Integer] Unicode codepoint
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# @return [Boolean]
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def includes?(character)
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@unicodes.key?(character)
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end
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# Get character code for Unicode codepoint.
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#
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# @param character [Integer] Unicode codepoint
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# @return [Integer]
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def from_unicode(character)
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@unicodes[character]
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end
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# Get `cmap` table for this subset.
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#
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# @return [TTFunk::Table::Cmap]
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def new_cmap_table
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@new_cmap_table ||=
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begin
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mapping =
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@subset.each_with_object({}) do |(code, unicode), map|
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map[code] = unicode_cmap[unicode]
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map
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end
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# since we're mapping a subset of the unicode glyphs into an
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# arbitrary 256-character space, the actual encoding we're
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# using is irrelevant. We choose MacRoman because it's a 256-character
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# encoding that happens to be well-supported in both TTF and
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# PDF formats.
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TTFunk::Table::Cmap.encode(mapping, :mac_roman)
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end
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end
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# Get the list of Glyph IDs from the original font that are in this
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# subset.
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#
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# @return [Array<Integer>]
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def original_glyph_ids
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([0] + @unicodes.keys.map { |unicode| unicode_cmap[unicode] }).uniq.sort
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end
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end
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end
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end
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