prawn:Prawn::Font::AFM#compute_width_of
#!/usr/bin/env ruby require "prawn" pdf = Prawn::Document.new f = Prawn::Font::AFM.new(pdf, "Times-Roman") p f.compute_width_of("a") p f.compute_width_of("ab") p f.compute_width_of("abc")
で、
5.328 11.328 16.656