thodg/exterm/lib/ttf.ex

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• Hash : 4493aa9d
  Author : Thomas de Grivel
  Date : 2022-02-11T13:44:03
  

  ttf WIP

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• lib/ttf.ex

• defmodule TTF do
    use Bitwise
  
    defstruct bounding_box: nil, cmap: [], cmap_subtable_count: nil, data: nil, glyph_count: nil, glyph_locations: nil, header: nil, loca_offset_format: nil, magic: nil, path: nil, table_count: nil, units_per_em: nil
  
    @cmap_platform_id_unicode   0
    @cmap_unicode_2_bmp_only      3
    @cmap_platform_id_apple     1
    @cmap_platform_id_microsoft 3
    @cmap_microsoft_unicode_bmp   1
    @valid_head_magics   [0x5F0F3CF5]
    @valid_head_versions [0x00010000]
    @valid_magics        [0x00010000]
    @valid_maxp_versions [0x00010000]
  
    def load(path) do
      IO.inspect([TTF, :load, path])
      File.read!(path)
      |> parse(path)
    end
  
    def parse(data, path \\ nil) do
      %__MODULE__{data: data, path: path}
      |> parse_header()
      |> parse_maxp()
      |> parse_cmap()
      |> parse_head()
      |> parse_loca()
      |> parse_glyphs()
      |> IO.inspect()
    end
  
    def parse_header(ttf = %__MODULE__{data: <<magic::unsigned-big-32, rest::binary>>, magic: nil}) do
      if ! Enum.find(@valid_magics, & &1 == magic) do
        raise ArgumentError, "invalid magic #{magic}"
      end
      %__MODULE__{ttf | magic: magic}
      |> parse_header(rest)
    end
    def parse_header(ttf = %__MODULE__{header: nil}, <<table_count::unsigned-big-16, _::size(16), _::size(16), _::size(16), rest::binary>>) do
      %__MODULE__{ttf | header: %{}, table_count: table_count}
      |> parse_header_table(rest, 0)
    end
    def parse_header(ttf, <<_::binary>>) do
      ttf
    end
  
    def parse_header_table(ttf = %{table_count: table_count}, <<rest::binary>>, i) when i >= table_count do
      ttf
      |> parse_header(rest)
    end
    def parse_header_table(ttf, <<tag0, tag1, tag2, tag3, checksum::unsigned-big-32, offset::unsigned-big-32, size::unsigned-big-32, rest::binary>>, i) do
      tag = to_string([tag0, tag1, tag2, tag3])
      header = ttf.header
      |> Map.put(tag, %{tag: tag, checksum: checksum, offset: offset, size: size})
      %__MODULE__{ttf | header: header}
      |> parse_header_table(rest, i + 1)
    end
  
    def table(ttf, name) do
      offset = ttf.header[name].offset
      size = ttf.header[name].size
      <<_::binary-size(offset), table_data::binary-size(size), _::binary>> = ttf.data
      table_data
    end
  
    def parse_maxp(ttf) do
      maxp = table(ttf, "maxp")
      <<version::unsigned-big-32, glyph_count::unsigned-big-16, _::binary>> = maxp
      if ! Enum.find(@valid_maxp_versions, & &1 == version) do
        raise ArgumentError, "invalid maxp version #{version}"
      end
      %__MODULE__{ttf | glyph_count: glyph_count}
    end
  
    def parse_cmap(ttf) do
      cmap = table(ttf, "cmap")
      <<version::unsigned-big-16, subtable_count::unsigned-big-16, rest::binary>> = cmap
      %__MODULE__{ttf | cmap_subtable_count: subtable_count, cmap: []}
      |> parse_cmap_subtable(cmap, rest, 0)
    end
  
    def parse_cmap_subtable(ttf = %__MODULE__{cmap_subtable_count: count}, _, _, i) when i >= count do
      ttf
    end
    def parse_cmap_subtable(ttf, cmap, <<platform_id::unsigned-big-16, platform_specific_id::unsigned-big-16, offset::unsigned-big-32, rest::binary>>, i) do
      ttf
      |> parse_cmap_subtable(cmap, rest, i, platform_id, platform_specific_id, offset)
    end
    def parse_cmap_subtable(ttf, cmap, binary, i, @cmap_platform_id_unicode, @cmap_unicode_2_bmp_only, offset) do
      ttf
      |> parse_cmap_subtable(cmap, binary, i + 1)
    end
    def parse_cmap_subtable(ttf, cmap, binary, i, @cmap_platform_id_apple, _, offset) do
      ttf
      |> parse_cmap_subtable(cmap, binary, i + 1)
    end
    def parse_cmap_subtable(ttf, cmap, binary, i, @cmap_platform_id_microsoft, @cmap_microsoft_unicode_bmp, offset) do
      <<_::binary-size(offset), format::unsigned-big-16, rest::binary>> = cmap
      if format != 4 do
        raise ArgumentError, "invalid cmap subtable format #{format}"
      end
      table_start_rest_byte_size = byte_size(rest) + 2
      <<subtable_length::unsigned-big-16, _language_code::unsigned-big-16, segment_count::unsigned-big-16, _search_range::unsigned-big-16, _entry_selector::unsigned-big-16, _range_shift::unsigned-big-16, rest::binary>> = rest
      segment_count = trunc(segment_count / 2)
      {end_codes, rest} = parse_cmap_subtable_array(rest, segment_count)
      <<_::unsigned-16, rest::binary>> = rest
      {start_codes, rest} = parse_cmap_subtable_array(rest, segment_count)
      {id_deltas, rest} = parse_cmap_subtable_array(rest, segment_count)
      {id_range_offsets, rest} = parse_cmap_subtable_array(rest, segment_count)
      {start_codes, rest} = parse_cmap_subtable_array(rest, segment_count)
      glyph_index_array_size = trunc((subtable_length - (table_start_rest_byte_size - byte_size(rest))) / 2)
      id_deltas = id_deltas |> Tuple.to_list() |> Enum.map(&ub16_to_signed/1) |> List.to_tuple()
      glyph_indexes = parse_cmap_subtable_array(rest, glyph_index_array_size)
      subtable = %{platform_id: @cmap_platform_id_microsoft, platform_specific_id: @cmap_microsoft_unicode_bmp, segment_count: segment_count, end_codes: end_codes, start_codes: start_codes, id_deltas: id_deltas, id_range_offsets: id_range_offsets, glyph_indexes: glyph_indexes}
      %__MODULE__{ttf | cmap: [subtable | ttf.cmap]}
      |> parse_cmap_subtable(cmap, rest, i + 1)
    end
  
    def parse_cmap_subtable_array(subtable, size) do
      parse_cmap_subtable_array(subtable, size, [])
    end
    def parse_cmap_subtable_array(rest, 0, acc) do
      {acc |> Enum.reverse() |> List.to_tuple(), rest}
    end
    def parse_cmap_subtable_array(<<ub16::unsigned-big-16, rest::binary>>, size, acc) do
      parse_cmap_subtable_array(rest, size - 1, [ub16 | acc])
    end
  
    def ub16_to_signed(ub16) do
      if (band(0b1000000000000000, ub16) != 0) do
        - band(0xFFFF, bnot(ub16)) - 1
      else
        ub16
      end
    end
  
    def parse_head(ttf) do
      head = table(ttf, "head")
      <<version::unsigned-big-32, _::binary-size(8), magic::unsigned-big-32, rest::binary>> = head
      if ! Enum.find(@valid_head_versions, & &1 == version) do
        raise ArgumentError, "invalid head version #{version}"
      end
      if ! Enum.find(@valid_head_magics, & &1 == magic) do
        raise ArgumentError, "invalid head magic #{magic}"
      end
      <<_::binary-size(2), units_per_em::unsigned-big-16, _::binary-size(16), bb1::unsigned-big-16, bb2::unsigned-big-16, bb3::unsigned-big-16, bb4::unsigned-big-16, _::binary-size(6), loca_offset_format::unsigned-big-16, _::binary>> = rest
      loca_offset_format = if loca_offset_format == 0, do: :short, else: :long
      %__MODULE__{ttf | units_per_em: units_per_em, bounding_box: {bb1, bb2, bb3, bb4}, loca_offset_format: loca_offset_format}
    end
  
    def parse_loca(ttf) do
      loca = table(ttf, "loca")
      ttf
      |> parse_loca(loca, 0, ttf.glyph_count + 1, [])
    end
  
    def parse_loca(ttf, _, i, max, acc) when (i >= max) do
      glyph_locations = acc |> Enum.reverse() |> List.to_tuple()
      %__MODULE__{ttf | glyph_locations: glyph_locations}
    end
    def parse_loca(ttf, loca, i, max, acc) do
      if ttf.loca_offset_format == :short do
        <<first::unsigned-big-16, rest::binary>> = loca
        parse_loca(ttf, rest, i + 1, max, [first * 2 | acc])
      else
        <<first::unsigned-big-32, rest::binary>> = loca
        parse_loca(ttf, rest, i + 1, max, [first | acc])
      end
    end
  
    def parse_glyphs(ttf) do
      ttf
    end
  
    def parse_glyph(ttf = %{glyphs: glyphs}, index) do
      ttf
    end
  
    def codepoint_to_font_index(font, codepoint) do
      codepoint_to_font_index(font, codepoint, 0, hd(font.cmap).segment_count)
    end
    def codepoint_to_font_index(font, codepoint, i, segment_count) when i >= segment_count do
      nil
    end
    def codepoint_to_font_index(font, codepoint, i, _segment_count) do
      start_code = elem(hd(font.cmap).start_codes, i)
      end_code = elem(hd(font.cmap).end_codes, i)
      if start_code <= codepoint && codepoint <= end_code do
        id_range_offset = elem(hd(font.cmap).id_range_offsets, i)
        id_delta = elem(hd(font.cmap).id_deltas, i)
        if (id_range_offset == 0) do
          band(0xFFFF, (codepoint + id_delta))
        else
          glyph_index_offset = i + bsr(id_range_offset, 1) + codepoint - start_code - hd(font.cmap).segment_count
          glyph_index = elem(hd(font.cmap).glyph_indexes, glyph_index_offset)
          band(0xFFFF, (glyph_index + id_delta))
        end
      else
        nil
      end
    end
    def has_glyph?(ttf, codepoint) do
      if codepoint_to_font_index(ttf, codepoint) do
        true
      else
        false
      end
    end
  
    def glyph(ttf, codepoint) do
      id = codepoint_to_font_index(ttf, codepoint) || 0
      glyf = table(ttf, "glyf")
      
      nil
    end
  end
  

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