Merge pull request #24 from mustmodify/patch-1

add example to get width of a string

examples/character-or-string-width.rb

@@ -0,0 +1,43 @@
+require 'rubygems'
+require 'ttfunk'
+require 'valuable'
+# 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
+
+class Font
+  attr_reader :file
+
+  def initialize(path_to_file)
+    @file = TTFunk::File.open(path_to_file)
+  end
+
+  def width_of( string )
+    string.split('').map{|char| character_width( char )}.inject{|sum, x| sum + x}
+  end
+
+  def character_width( character )
+    width_in_units = ( horizontal_metrics.for( glyph_id( character )).advance_width )
+    width_in_units.to_f / units_per_em
+  end
+
+  def units_per_em
+    @u_per_em ||= file.header.units_per_em
+  end
+
+  def horizontal_metrics
+    @hm = file.horizontal_metrics
+  end
+
+  def glyph_id(character)
+    character_code = character.unpack("U*").first
+    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.