Add figure plugin.

Author: trainman419

_plugins/figure.rb

@@ -0,0 +1,22 @@
+# Generate a figure such as:
+# <figure>
+#   <img src="/media/2014/02/16/parallel.jpg"/>
+#   <figcaption>Path planning is hard</figcaption>
+# </figure>
+
+module Jekyll
+  class FigureTag < Liquid::Tag
+
+    def initialize(tag_name, text, tokens)
+      super
+      @src, _, @caption = text.partition(" ")
+      @caption.chomp!(" ")
+    end
+
+    def render(context)
+      "<figure><img src=\"#{@src}\" alt=\"#{@caption}\" title=\"#{@caption}\"/><figcaption>#{@caption}</figcaption></figure>"
+    end
+  end
+end
+
+Liquid::Template.register_tag('figure', Jekyll::FigureTag)

_posts/2014-02-16-path-planning.markdown

@@ -12,7 +12,7 @@ I've spent the last few months experimenting with path planning for Dagny.
 
 Dagny is an car-type robot, which means that I have a very constrained set of possible motions. In particular, I can move forwards and backwards, and can turn while moving, but can't turn in place or move sideways. If you've ever driven a car and tried to parallel park, you can understand how difficult it can be to maneuver a car-type vehicle.
 
-![Parking](/media/2014/02/16/parallel.jpg)
+{% figure /media/2014/02/16/parallel.jpg Path planning is hard %}
 
 These motion constraints mean that I have to make sure that the motion planners understand the motion constraints and can generate a path that doesn't have turn-in-place behaviors, and honors the minimum turning radius of the robot.
 
@@ -105,17 +105,11 @@ Since we can't solve directly for the path parameters, we cheat and run a numeri
 
 The current solution simply searches for all primitives whose end point is within one minimum turning radius of the robot's start position. This produces a significant number of overlapping primitives:
 
-![Motion Primitives](/media/2014/02/16/mprim_0.png "Paths with starting angle 0")
+{% figure /media/2014/02/16/mprim_0.png Paths with starting angle 0 %}
 
-Paths with starting angle 0
+{% figure /media/2014/02/16/mprim_1.png Paths with starting angle 1 %}
 
-![Motion Primitives](/media/2014/02/16/mprim_1.png "Paths with starting angle 1")
-
-Paths with starting angle 1
-
-![Motion Primitives](/media/2014/02/16/mprim_2.png "Paths with starting angle 2")
-
-Paths with starting angle 2
+{% figure /media/2014/02/16/mprim_2.png Paths with starting angle 2 %}
 
 My next steps will be to:
  * Find a solution for eliminating redundant motion primitives