Class: TTFunk::Table::OS2

Inherits:
TTFunk::Table show all
Defined in:
lib/ttfunk/table/os2.rb

Overview

OS/2 and Windows Metrics (‘OS/2`) table

Constant Summary collapse

CODE_PAGE_BITS =

Code page bits.

{
  1252 => 0,
  1250 => 1,
  1251 => 2,
  1253 => 3,
  1254 => 4,
  1255 => 5,
  1256 => 6,
  1257 => 7,
  1258 => 8,
  874 => 16,
  932 => 17,
  936 => 18,
  949 => 19,
  950 => 20,
  1361 => 21,
  10_000 => 29,
  869 => 48,
  866 => 49,
  865 => 50,
  864 => 51,
  863 => 52,
  862 => 53,
  861 => 54,
  860 => 55,
  857 => 56,
  855 => 57,
  852 => 58,
  775 => 59,
  737 => 60,
  708 => 61,
  850 => 62,
  437 => 63,
}.freeze
UNICODE_BLOCKS =

Unicode blocks.

{
  (0x0000..0x007F) => 0,
  (0x0080..0x00FF) => 1,
  (0x0100..0x017F) => 2,
  (0x0180..0x024F) => 3,
  (0x0250..0x02AF) => 4,
  (0x1D00..0x1D7F) => 4,
  (0x1D80..0x1DBF) => 4,
  (0x02B0..0x02FF) => 5,
  (0xA700..0xA71F) => 5,
  (0x0300..0x036F) => 6,
  (0x1DC0..0x1DFF) => 6,
  (0x0370..0x03FF) => 7,
  (0x2C80..0x2CFF) => 8,
  (0x0400..0x04FF) => 9,
  (0x0500..0x052F) => 9,
  (0x2DE0..0x2DFF) => 9,
  (0xA640..0xA69F) => 9,
  (0x0530..0x058F) => 10,
  (0x0590..0x05FF) => 11,
  (0xA500..0xA63F) => 12,
  (0x0600..0x06FF) => 13,
  (0x0750..0x077F) => 13,
  (0x07C0..0x07FF) => 14,
  (0x0900..0x097F) => 15,
  (0x0980..0x09FF) => 16,
  (0x0A00..0x0A7F) => 17,
  (0x0A80..0x0AFF) => 18,
  (0x0B00..0x0B7F) => 19,
  (0x0B80..0x0BFF) => 20,
  (0x0C00..0x0C7F) => 21,
  (0x0C80..0x0CFF) => 22,
  (0x0D00..0x0D7F) => 23,
  (0x0E00..0x0E7F) => 24,
  (0x0E80..0x0EFF) => 25,
  (0x10A0..0x10FF) => 26,
  (0x2D00..0x2D2F) => 26,
  (0x1B00..0x1B7F) => 27,
  (0x1100..0x11FF) => 28,
  (0x1E00..0x1EFF) => 29,
  (0x2C60..0x2C7F) => 29,
  (0xA720..0xA7FF) => 29,
  (0x1F00..0x1FFF) => 30,
  (0x2000..0x206F) => 31,
  (0x2E00..0x2E7F) => 31,
  (0x2070..0x209F) => 32,
  (0x20A0..0x20CF) => 33,
  (0x20D0..0x20FF) => 34,
  (0x2100..0x214F) => 35,
  (0x2150..0x218F) => 36,
  (0x2190..0x21FF) => 37,
  (0x27F0..0x27FF) => 37,
  (0x2900..0x297F) => 37,
  (0x2B00..0x2BFF) => 37,
  (0x2200..0x22FF) => 38,
  (0x2A00..0x2AFF) => 38,
  (0x27C0..0x27EF) => 38,
  (0x2980..0x29FF) => 38,
  (0x2300..0x23FF) => 39,
  (0x2400..0x243F) => 40,
  (0x2440..0x245F) => 41,
  (0x2460..0x24FF) => 42,
  (0x2500..0x257F) => 43,
  (0x2580..0x259F) => 44,
  (0x25A0..0x25FF) => 45,
  (0x2600..0x26FF) => 46,
  (0x2700..0x27BF) => 47,
  (0x3000..0x303F) => 48,
  (0x3040..0x309F) => 49,
  (0x30A0..0x30FF) => 50,
  (0x31F0..0x31FF) => 50,
  (0x3100..0x312F) => 51,
  (0x31A0..0x31BF) => 51,
  (0x3130..0x318F) => 52,
  (0xA840..0xA87F) => 53,
  (0x3200..0x32FF) => 54,
  (0x3300..0x33FF) => 55,
  (0xAC00..0xD7AF) => 56,
  (0xD800..0xDFFF) => 57,
  (0x10900..0x1091F) => 58,
  (0x4E00..0x9FFF) => 59,
  (0x2E80..0x2EFF) => 59,
  (0x2F00..0x2FDF) => 59,
  (0x2FF0..0x2FFF) => 59,
  (0x3400..0x4DBF) => 59,
  (0x20000..0x2A6DF) => 59,
  (0x3190..0x319F) => 59,
  (0xE000..0xF8FF) => 60,
  (0x31C0..0x31EF) => 61,
  (0xF900..0xFAFF) => 61,
  (0x2F800..0x2FA1F) => 61,
  (0xFB00..0xFB4F) => 62,
  (0xFB50..0xFDFF) => 63,
  (0xFE20..0xFE2F) => 64,
  (0xFE10..0xFE1F) => 65,
  (0xFE30..0xFE4F) => 65,
  (0xFE50..0xFE6F) => 66,
  (0xFE70..0xFEFF) => 67,
  (0xFF00..0xFFEF) => 68,
  (0xFFF0..0xFFFF) => 69,
  (0x0F00..0x0FFF) => 70,
  (0x0700..0x074F) => 71,
  (0x0780..0x07BF) => 72,
  (0x0D80..0x0DFF) => 73,
  (0x1000..0x109F) => 74,
  (0x1200..0x137F) => 75,
  (0x1380..0x139F) => 75,
  (0x2D80..0x2DDF) => 75,
  (0x13A0..0x13FF) => 76,
  (0x1400..0x167F) => 77,
  (0x1680..0x169F) => 78,
  (0x16A0..0x16FF) => 79,
  (0x1780..0x17FF) => 80,
  (0x19E0..0x19FF) => 80,
  (0x1800..0x18AF) => 81,
  (0x2800..0x28FF) => 82,
  (0xA000..0xA48F) => 83,
  (0xA490..0xA4CF) => 83,
  (0x1700..0x171F) => 84,
  (0x1720..0x173F) => 84,
  (0x1740..0x175F) => 84,
  (0x1760..0x177F) => 84,
  (0x10300..0x1032F) => 85,
  (0x10330..0x1034F) => 86,
  (0x10400..0x1044F) => 87,
  (0x1D000..0x1D0FF) => 88,
  (0x1D100..0x1D1FF) => 88,
  (0x1D200..0x1D24F) => 88,
  (0x1D400..0x1D7FF) => 89,
  (0xF0000..0xFFFFD) => 90,
  (0x100000..0x10FFFD) => 90,
  (0xFE00..0xFE0F) => 91,
  (0xE0100..0xE01EF) => 91,
  (0xE0000..0xE007F) => 92,
  (0x1900..0x194F) => 93,
  (0x1950..0x197F) => 94,
  (0x1980..0x19DF) => 95,
  (0x1A00..0x1A1F) => 96,
  (0x2C00..0x2C5F) => 97,
  (0x2D30..0x2D7F) => 98,
  (0x4DC0..0x4DFF) => 99,
  (0xA800..0xA82F) => 100,
  (0x10000..0x1007F) => 101,
  (0x10080..0x100FF) => 101,
  (0x10100..0x1013F) => 101,
  (0x10140..0x1018F) => 102,
  (0x10380..0x1039F) => 103,
  (0x103A0..0x103DF) => 104,
  (0x10450..0x1047F) => 105,
  (0x10480..0x104AF) => 106,
  (0x10800..0x1083F) => 107,
  (0x10A00..0x10A5F) => 108,
  (0x1D300..0x1D35F) => 109,
  (0x12000..0x123FF) => 110,
  (0x12400..0x1247F) => 110,
  (0x1D360..0x1D37F) => 111,
  (0x1B80..0x1BBF) => 112,
  (0x1C00..0x1C4F) => 113,
  (0x1C50..0x1C7F) => 114,
  (0xA880..0xA8DF) => 115,
  (0xA900..0xA92F) => 116,
  (0xA930..0xA95F) => 117,
  (0xAA00..0xAA5F) => 118,
  (0x10190..0x101CF) => 119,
  (0x101D0..0x101FF) => 120,
  (0x102A0..0x102DF) => 121,
  (0x10280..0x1029F) => 121,
  (0x10920..0x1093F) => 121,
  (0x1F030..0x1F09F) => 122,
  (0x1F000..0x1F02F) => 122,
}.freeze
UNICODE_MAX =

Indicates that font supports supplementary characters.

0xFFFF
UNICODE_RANGES =

Unicode block ranges.

UNICODE_BLOCKS.keys.sort_by(&:max).freeze
LOWERCASE_START =

Start chracter for average character width calculation.

'a'.ord
LOWERCASE_END =

End chracter for average character width calculation.

'z'.ord
LOWERCASE_COUNT =

Number of chracters for average character width calculation.

(LOWERCASE_END - LOWERCASE_START) + 1
CODEPOINT_SPACE =

Space character code point.

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SPACE_GLYPH_MISSING_ERROR =

Error message for missing space character.

"Space glyph (0x#{CODEPOINT_SPACE.to_s(16)}) must be included in the font"
WEIGHT_SPACE =

Used to calculate the xAvgCharWidth field. From docs.microsoft.com/en-us/typography/opentype/spec/os2:

“When first defined, the specification was biased toward Basic Latin characters, and it was thought that the xAvgCharWidth value could be used to estimate the average length of lines of text. A formula for calculating xAvgCharWidth was provided using frequency-of-use weighting factors for lowercase letters a - z.”

The array below contains 26 weight values which correspond to the 26 letters in the Latin alphabet. Each weight is the relative frequency of that letter in the English language.

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WEIGHT_LOWERCASE =

chracter weights for average character width calculation.

[
  64, 14, 27, 35, 100, 20, 14, 42, 63, 3, 6, 35, 20,
  56, 56, 17, 4, 49, 56, 71, 31, 10, 18, 3, 18, 2,
].freeze

Instance Attribute Summary collapse

Attributes inherited from TTFunk::Table

#file, #length, #offset

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from TTFunk::Table

#exists?, #initialize, #raw

Constructor Details

This class inherits a constructor from TTFunk::Table

Instance Attribute Details

#ascent ⇒ Integer (readonly)

The typographic ascender for this font.

Returns:

  • (Integer) 


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# File 'lib/ttfunk/table/os2.rb', line 100

def ascent
  @ascent
end

#ave_char_width ⇒ Integer (readonly)

Average weighted escapement.

Returns:

  • (Integer) 


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# File 'lib/ttfunk/table/os2.rb', line 16

def ave_char_width
  @ave_char_width
end

#break_char ⇒ Integer (readonly)

The Unicode code point, in UTF-16 encoding, of a character that can be used as a default break character.

Returns:

  • (Integer) 


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# File 'lib/ttfunk/table/os2.rb', line 141

def break_char
  @break_char
end

#cap_height ⇒ Integer (readonly)

The distance between the baseline and the approximate height of uppercase letters.

Returns:

  • (Integer) 


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# File 'lib/ttfunk/table/os2.rb', line 130

def cap_height
  @cap_height
end

#char_range ⇒ Integer (readonly)

Unicode Character Range.

Returns:

  • (Integer) 


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# File 'lib/ttfunk/table/os2.rb', line 80

def char_range
  @char_range
end

#code_page_range ⇒ Integer (readonly)

Code Page Character Range.

Returns:

  • (Integer) 


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# File 'lib/ttfunk/table/os2.rb', line 120

def code_page_range
  @code_page_range
end

#default_char ⇒ Integer (readonly)

The Unicode code point, in UTF-16 encoding, of a character that can be used for a default glyph if a requested character is not supported in the font.

Returns:

  • (Integer) 


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# File 'lib/ttfunk/table/os2.rb', line 136

def default_char
  @default_char
end

#descent ⇒ Integer (readonly)

The typographic descender for this font.

Returns:

  • (Integer) 


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# File 'lib/ttfunk/table/os2.rb', line 104

def descent
  @descent
end

#family_class ⇒ Integer (readonly)

Font-family class and subclass.

Returns:

  • (Integer) 


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# File 'lib/ttfunk/table/os2.rb', line 72

def family_class
  @family_class
end

#first_char_index ⇒ Integer (readonly)

The minimum Unicode index (character code) in this font.

Returns:

  • (Integer) 


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# File 'lib/ttfunk/table/os2.rb', line 92

def first_char_index
  @first_char_index
end

#last_char_index ⇒ Integer (readonly)

The maximum Unicode index (character code) in this font.

Returns:

  • (Integer) 


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# File 'lib/ttfunk/table/os2.rb', line 96

def last_char_index
  @last_char_index
end

#line_gap ⇒ Integer (readonly)

The typographic line gap for this font.

Returns:

  • (Integer) 


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# File 'lib/ttfunk/table/os2.rb', line 108

def line_gap
  @line_gap
end

#max_context ⇒ Integer (readonly)

The maximum length of a target glyph context for any feature in this font.

Returns:

  • (Integer) 


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# File 'lib/ttfunk/table/os2.rb', line 146

def max_context
  @max_context
end

#panose ⇒ Integer (readonly)

PANOSE classification number.

Returns:

  • (Integer) 


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# File 'lib/ttfunk/table/os2.rb', line 76

def panose
  @panose
end

#selection ⇒ Integer (readonly)

Font selection flags.

Returns:

  • (Integer) 


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# File 'lib/ttfunk/table/os2.rb', line 88

def selection
  @selection
end

#type ⇒ Integer (readonly)

Type flags.

Returns:

  • (Integer) 


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# File 'lib/ttfunk/table/os2.rb', line 28

def type
  @type
end

#vendor_id ⇒ String (readonly)

Font Vendor Identification.

Returns:

  • (String) 


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# File 'lib/ttfunk/table/os2.rb', line 84

def vendor_id
  @vendor_id
end

#version ⇒ Integer (readonly)

Table version.

Returns:

  • (Integer) 


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# File 'lib/ttfunk/table/os2.rb', line 12

def version
  @version
end

#weight_class ⇒ Integer (readonly)

Weight class.

Returns:

  • (Integer) 


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# File 'lib/ttfunk/table/os2.rb', line 20

def weight_class
  @weight_class
end

#width_class ⇒ Integer (readonly)

Width class.

Returns:

  • (Integer) 


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# File 'lib/ttfunk/table/os2.rb', line 24

def width_class
  @width_class
end

#win_ascent ⇒ Integer (readonly)

The “Windows ascender” metric.

Returns:

  • (Integer) 


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# File 'lib/ttfunk/table/os2.rb', line 112

def win_ascent
  @win_ascent
end

#win_descent ⇒ Integer (readonly)

The “Windows descender” metric.

Returns:

  • (Integer) 


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# File 'lib/ttfunk/table/os2.rb', line 116

def win_descent
  @win_descent
end

#x_height ⇒ Integer (readonly)

The distance between the baseline and the approximate height of non-ascending lowercase letters.

Returns:

  • (Integer) 


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# File 'lib/ttfunk/table/os2.rb', line 125

def x_height
  @x_height
end

#y_strikeout_position ⇒ Integer (readonly)

Strikeout position.

Returns:

  • (Integer) 


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# File 'lib/ttfunk/table/os2.rb', line 68

def y_strikeout_position
  @y_strikeout_position
end

#y_strikeout_size ⇒ Integer (readonly)

Strikeout size.

Returns:

  • (Integer) 


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# File 'lib/ttfunk/table/os2.rb', line 64

def y_strikeout_size
  @y_strikeout_size
end

#y_subscript_x_offset ⇒ Integer (readonly)

Subscript x offset.

Returns:

  • (Integer) 


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# File 'lib/ttfunk/table/os2.rb', line 40

def y_subscript_x_offset
  @y_subscript_x_offset
end

#y_subscript_x_size ⇒ Integer (readonly)

Subscript horizontal font size.

Returns:

  • (Integer) 


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# File 'lib/ttfunk/table/os2.rb', line 32

def y_subscript_x_size
  @y_subscript_x_size
end

#y_subscript_y_offset ⇒ Integer (readonly)

Subscript y offset.

Returns:

  • (Integer) 


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# File 'lib/ttfunk/table/os2.rb', line 44

def y_subscript_y_offset
  @y_subscript_y_offset
end

#y_subscript_y_size ⇒ Integer (readonly)

Subscript vertical font size.

Returns:

  • (Integer) 


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# File 'lib/ttfunk/table/os2.rb', line 36

def y_subscript_y_size
  @y_subscript_y_size
end

#y_superscript_x_offset ⇒ Integer (readonly)

Superscript x offset.

Returns:

  • (Integer) 


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# File 'lib/ttfunk/table/os2.rb', line 56

def y_superscript_x_offset
  @y_superscript_x_offset
end

#y_superscript_x_size ⇒ Integer (readonly)

Superscript horizontal font size.

Returns:

  • (Integer) 


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# File 'lib/ttfunk/table/os2.rb', line 48

def y_superscript_x_size
  @y_superscript_x_size
end

#y_superscript_y_offset ⇒ Integer (readonly)

Superscript y offset.

Returns:

  • (Integer) 


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# File 'lib/ttfunk/table/os2.rb', line 60

def y_superscript_y_offset
  @y_superscript_y_offset
end

#y_superscript_y_size ⇒ Integer (readonly)

Superscript vertical font size.

Returns:

  • (Integer) 


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# File 'lib/ttfunk/table/os2.rb', line 52

def y_superscript_y_size
  @y_superscript_y_size
end

Class Method Details

.encode(os2, subset) ⇒ String

Encode table.

Parameters:

Returns:

  • (String) 


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# File 'lib/ttfunk/table/os2.rb', line 411

def encode(os2, subset)
  result = ''.b
  result << [
    os2.version, avg_char_width_for(os2, subset), os2.weight_class,
    os2.width_class, os2.type, os2.y_subscript_x_size,
    os2.y_subscript_y_size, os2.y_subscript_x_offset,
    os2.y_subscript_y_offset, os2.y_superscript_x_size,
    os2.y_superscript_y_size, os2.y_superscript_x_offset,
    os2.y_superscript_y_offset, os2.y_strikeout_size,
    os2.y_strikeout_position, os2.family_class,
  ].pack('n*')

  result << os2.panose

  new_char_range = unicode_blocks_for(os2, os2.char_range, subset)
  result << BinUtils
    .slice_int(
      new_char_range.value,
      bit_width: 32,
      slice_count: 4,
    )
    .pack('N*')

  result << os2.vendor_id

  new_cmap_table = subset.new_cmap_table[:charmap]
  code_points = new_cmap_table
    .keys
    .select { |k| (new_cmap_table[k][:new]).positive? }
    .sort

  # "This value depends on which character sets the font supports.
  # This field cannot represent supplementary character values
  # (codepoints greater than 0xFFFF). Fonts that support
  # supplementary characters should set the value in this field
  # to 0xFFFF."
  first_char_index = [code_points.first || 0, UNICODE_MAX].min
  last_char_index = [code_points.last || 0, UNICODE_MAX].min

  result << [
    os2.selection, first_char_index, last_char_index,
  ].pack('n*')

  if os2.version.positive?
    result << [
      os2.ascent, os2.descent, os2.line_gap,
      os2.win_ascent, os2.win_descent,
    ].pack('n*')

    result << BinUtils
      .slice_int(
        code_pages_for(subset).value,
        bit_width: 32,
        slice_count: 2,
      )
      .pack('N*')

    if os2.version > 1
      result << [
        os2.x_height, os2.cap_height, os2.default_char,
        os2.break_char, os2.max_context,
      ].pack('n*')
    end
  end

  result
end

Instance Method Details

#tag ⇒ String

Table tag.

Returns:

  • (String) 


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# File 'lib/ttfunk/table/os2.rb', line 400

def tag
  'OS/2'
end