Render tex formulas to images

lib/gollum/tex.rb

@@ -0,0 +1,73 @@
+require 'fileutils'
+require 'shellwords'
+require 'tmpdir'
+
+module Gollum
+  module Tex
+    Template = <<-EOS
+\\documentclass[12pt]{article}
+\\usepackage{color}
+\\usepackage[dvips]{graphicx}
+\\pagestyle{empty}
+\\pagecolor{white}
+\\begin{document}
+{\\color{black}
+\\begin{eqnarray*}
+%s
+\\end{eqnarray*}}
+\\end{document}
+    EOS
+
+    class << self
+      attr_accessor :latex_path, :dvips_path, :convert_path
+    end
+
+    self.latex_path   = 'latex'
+    self.dvips_path   = 'dvips'
+    self.convert_path = 'convert'
+
+    def self.check_dependencies!
+      if `which latex` == ""
+        raise "`latex` command not found"
+      end
+
+      if `which dvips` == ""
+        raise "`dvips` command not found"
+      end
+
+      if `which convert` == ""
+        raise "`convert` command not found"
+      end
+    end
+
+    def self.render_formula(formula)
+      check_dependencies!
+
+      Dir.mktmpdir('tex') do |path|
+        tex_path = ::File.join(path, 'formula.tex')
+        dvi_path = ::File.join(path, 'formula.dvi')
+        eps_path = ::File.join(path, 'formula.eps')
+        png_path = ::File.join(path, 'formula.png')
+
+        ::File.open(tex_path, 'w') { |f| f.write(Template % formula) }
+
+        sh latex_path, '-interaction=batchmode', 'formula.tex', :cwd => path
+        sh dvips_path, '-o', eps_path, '-E', dvi_path
+        sh convert_path, '+adjoin',
+          '-antialias',
+          '-transparent', 'white',
+          '-density', '150x150',
+          eps_path, png_path
+
+        ::File.read(png_path)
+      end
+    end
+
+    private
+      def self.sh(*args)
+        options = args.last.is_a?(Hash) ? args.pop : {}
+        cwd     = "cd \"#{options[:cwd]}\" && " if options[:cwd]
+        `#{cwd}#{Shellwords.join(args)} 2>&1`
+      end
+  end
+end