write a converter to enable some syntaxes for now

Author: ocha-

_plugins/rhg_textile_converter.rb

@@ -0,0 +1,43 @@
+require "jekyll/converters/textile"
+module Jekyll::Converters
+  class RhgTextile < Textile
+    safe true
+
+    # set this :low before "jekyll serve" when you want to use only Jekyll::Converters::Textile
+    priority :high
+
+    RHG_CODE_RE = /`([^`]+)`/
+    RHG_IMAGE_RE = /^!(.+\.(?:jpg|png))\((.+)\)!/
+
+    def convert(content)
+      # try to enable the <code> syntax of the original RubyForge project,
+      # but not fully.
+      lines = content.lines
+      lines.map! { |line| line.gsub(RHG_CODE_RE) { "<code>#{$1}</code>" } }
+      content = lines.join
+
+      # try to apply the style for images of the original book
+      figc = 0
+      no_figc = content.include? %{class="image"}
+      content.gsub!(RHG_IMAGE_RE) do |m|
+        figc += 1
+        src, title = $~[1..2]
+        alt = "(" +  src.split(".").first.split("_").last + ")"
+        title = "Figure #{figc}: #{title}" unless no_figc
+        out = <<-EOS
+<p class="image">
+<img src="#{src}" alt="#{alt}"><br>
+#{title}
+</p>
+        EOS
+      end
+
+      super content
+    end
+
+    # simulate Jekyll::Converter.inherited
+    Jekyll::Converter.subclasses << self
+    Jekyll::Converter.subclasses.sort!
+  end
+end
+