1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
|
# frozen_string_literal: true
# Everything you never wanted to know about glyphs:
# http://chanae.walon.org/pub/ttf/ttf_glyphs.htm
# this code is a substantial reworking of:
# https://github.com/prawnpdf/ttfunk/blob/master/examples/metrics.rb
require 'ttfunk'
class Font
attr_reader :file
def initialize(path_to_file)
@file = TTFunk::File.open(path_to_file)
end
def width_of(string)
string.chars.sum { |char| character_width(char) }
end
def character_width(character)
width_in_units = horizontal_metrics.for(glyph_id(character)).advance_width
Float(width_in_units) / units_per_em
end
def units_per_em
@units_per_em ||= file.header.units_per_em
end
def horizontal_metrics
@horizontal_metrics ||= file.horizontal_metrics
end
def glyph_id(character)
character_code = character.unpack1('U*')
file.cmap.unicode.first[character_code]
end
end
# >> din = Font.new("#{File.dirname(__FILE__)}/../../fonts/DIN/DINPro-Light.ttf")
# >> din.width_of("Hypertension")
# => 5.832
# which is correct! Hypertension in that font takes up about 5.832 em! It's over by maybe ... 0.015.
|
