From 604f88939efc7f9f78dbdc22d1d75fc018842f48 Mon Sep 17 00:00:00 2001
From: Joshua Peek <josh@joshpeek.com>
Date: Mon, 24 Oct 2011 15:50:02 -0500
Subject: [PATCH] Render tex formulas to images

---
 lib/gollum.rb              |  1 +
 lib/gollum/frontend/app.rb |  8 ++++-
 lib/gollum/markup.rb       |  9 ++---
 lib/gollum/tex.rb          | 73 ++++++++++++++++++++++++++++++++++++++
 4 files changed, 83 insertions(+), 8 deletions(-)
 create mode 100644 lib/gollum/tex.rb

diff --git a/lib/gollum.rb b/lib/gollum.rb
index 1d9d595a..648adc50 100644
--- a/lib/gollum.rb
+++ b/lib/gollum.rb
@@ -17,6 +17,7 @@ require File.expand_path('../gollum/page', __FILE__)
 require File.expand_path('../gollum/file', __FILE__)
 require File.expand_path('../gollum/markup', __FILE__)
 require File.expand_path('../gollum/sanitization', __FILE__)
+require File.expand_path('../gollum/tex', __FILE__)
 
 module Gollum
   VERSION = '1.3.1'
diff --git a/lib/gollum/frontend/app.rb b/lib/gollum/frontend/app.rb
index 0026a329..f14eb4d0 100644
--- a/lib/gollum/frontend/app.rb
+++ b/lib/gollum/frontend/app.rb
@@ -144,6 +144,12 @@ module Precious
       mustache :compare
     end
 
+    get '/_tex.png' do
+      content_type 'image/png'
+      formula = Base64.decode64(params[:data])
+      Gollum::Tex.render_formula(formula)
+    end
+
     get %r{^/(javascript|css|images)} do
       halt 404
     end
@@ -199,7 +205,7 @@ module Precious
     end
 
     def update_wiki_page(wiki, page, content, commit_message, name = nil, format = nil)
-      return if !page ||  
+      return if !page ||
         ((!content || page.raw_data == content) && page.format == format)
       name    ||= page.name
       format    = (format || page.format).to_sym
diff --git a/lib/gollum/markup.rb b/lib/gollum/markup.rb
index 59f51a22..049730af 100644
--- a/lib/gollum/markup.rb
+++ b/lib/gollum/markup.rb
@@ -1,6 +1,7 @@
 require 'digest/sha1'
 require 'cgi'
 require 'pygments'
+require 'base64'
 
 module Gollum
 
@@ -97,13 +98,7 @@ module Gollum
     def process_tex(data)
       @texmap.each do |id, spec|
         type, tex = *spec
-        out =
-        case type
-          when :block
-            %{<script type="math/tex; mode=display">#{tex}</script>}
-          when :inline
-            %{<script type="math/tex">#{tex}</script>}
-        end
+        out = %{<img src="/_tex.png?type=#{type}&data=#{Base64.encode64(tex).chomp}" alt="#{CGI.escapeHTML(tex)}">}
         data.gsub!(id, out)
       end
       data
diff --git a/lib/gollum/tex.rb b/lib/gollum/tex.rb
new file mode 100644
index 00000000..df774226
--- /dev/null
+++ b/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