Class: Arrolio::FontMetrics::AfmMetrics

Inherits:
Object
  • Object
show all
Defined in:
lib/arrolio/font_metrics/afm_metrics.rb

Overview

Glyph-width lookup against Pdfrb's AFM data for one of the 14 PDF standard Type1 fonts.

Constant Summary collapse

UNITS_PER_EM = 
1000

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(font_name, afm) ⇒ AfmMetrics

Returns a new instance of AfmMetrics.



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# File 'lib/arrolio/font_metrics/afm_metrics.rb', line 12

def initialize(font_name, afm)
  @font_name = font_name.to_s
  @afm = afm
end

Instance Attribute Details

#afm ⇒ Object (readonly)

Returns the value of attribute afm.



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# File 'lib/arrolio/font_metrics/afm_metrics.rb', line 10

def afm
  @afm
end

#font_name ⇒ Object (readonly)

Returns the value of attribute font_name.



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# File 'lib/arrolio/font_metrics/afm_metrics.rb', line 10

def font_name
  @font_name
end

Class Method Details

.for_name(name) ⇒ Object 



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# File 'lib/arrolio/font_metrics/afm_metrics.rb', line 17

def self.for_name(name)
  afm = Pdfrb::Font::Type1::FontMetrics.for_standard_font(name.to_s)
  return nil unless afm

  new(name, afm)
end

Instance Method Details

#advance_width(char) ⇒ Object 



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# File 'lib/arrolio/font_metrics/afm_metrics.rb', line 28

def advance_width(char)
  metric = metric_for(char)
  metric ? metric[:width] : 0
end

#ascender(font_size: 12) ⇒ Object 



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# File 'lib/arrolio/font_metrics/afm_metrics.rb', line 38

def ascender(font_size: 12)
  (afm.ascender || 800) * font_size.to_f / units_per_em
end

#cap_height(font_size: 12) ⇒ Object 



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# File 'lib/arrolio/font_metrics/afm_metrics.rb', line 46

def cap_height(font_size: 12)
  (afm.cap_height || 700) * font_size.to_f / units_per_em
end

#descender(font_size: 12) ⇒ Object 



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# File 'lib/arrolio/font_metrics/afm_metrics.rb', line 42

def descender(font_size: 12)
  (afm.descender || -200) * font_size.to_f / units_per_em
end

#line_height(font_size:, line_spacing: 1.2) ⇒ Object 



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# File 'lib/arrolio/font_metrics/afm_metrics.rb', line 50

def line_height(font_size:, line_spacing: 1.2)
  ((afm.ascender || 800).to_f - (afm.descender || -200).to_f) *
    font_size.to_f / units_per_em * line_spacing.to_f
end

#units_per_em ⇒ Object 



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# File 'lib/arrolio/font_metrics/afm_metrics.rb', line 24

def units_per_em
  UNITS_PER_EM
end

#width_of_string(str, font_size:) ⇒ Object 



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# File 'lib/arrolio/font_metrics/afm_metrics.rb', line 33

def width_of_string(str, font_size:)
  scale = font_size.to_f / units_per_em
  str.each_char.sum { |c| advance_width(c) * scale }
end