diff --git a/lib/jekyll/responsive_image.rb b/lib/jekyll/responsive_image.rb
index 272b809..d5bb0eb 100644
--- a/lib/jekyll/responsive_image.rb
+++ b/lib/jekyll/responsive_image.rb
@@ -1,103 +1,8 @@
 require 'jekyll'
 require 'rmagick'
 
-module Jekyll
-  class ResponsiveImage
-    class Tag < Liquid::Tag
-      DEFAULT_QUALITY = 85
-
-      def initialize(tag_name, markup, tokens)
-        super
-
-        @attributes = {}
-        @markup = markup
-
-        @markup.scan(::Liquid::TagAttributes) do |key, value|
-          # Strip quotes from around attribute values
-          @attributes[key] = value.gsub(/^['"]|['"]$/, '')
-        end
-      end
-
-      def resize_image(img, config)
-        output_dir = config['output_dir']
-        ensure_output_dir_exists!(output_dir)
-
-        resized = []
-
-        config['sizes'].each do |size|
-          width = size['width']
-          ratio = width.to_f / img.columns.to_f
-          height = (img.rows.to_f * ratio).round
-
-          filename = resized_filename(img.filename, width, height)
-          filepath = "#{output_dir}/#{filename}"
-
-          next unless needs_resizing?(img, width)
-
-          resized.push(image_hash(filepath, width, height))
-
-          # Don't resize images more than once
-          next if File.exists?(filepath)
-
-          Jekyll.logger.info "Generating #{filepath}"
-
-          i = img.scale(ratio)
-          i.write(filepath) do |f|
-            f.quality = size['quality'] || DEFAULT_QUALITY
-          end
-
-          i.destroy!
-        end
-
-        resized
-      end
-
-      # Insert resize information into a file path
-      #
-      #   resized_filename(/foo/bar/file.name.jpg, 500, 300)
-      #     => /foo/bar/file.name-500x300.jpg
-      #
-      def resized_filename(path, width, height)
-        File.basename(path).sub(/\.([^.]+)$/, "-#{width}x#{height}.\\1")
-      end
-
-      def needs_resizing?(img, width)
-        img.columns > width
-      end
-
-      def ensure_output_dir_exists!(dir)
-        unless Dir.exists?(dir)
-          Jekyll.logger.info "Creating output directory #{dir}"
-          Dir.mkdir(dir)
-        end
-      end
-
-      # Build a hash containing image information
-      def image_hash(path, width, height)
-        {
-          'path'   => path,
-          'width'  => width,
-          'height' => height,
-        }
-      end
-
-      def render(context)
-        config = context.registers[:site].config['responsive_image']
-        config['output_dir'] ||= 'assets/resized'
-        config['sizes'] ||= []
-
-        img = Magick::Image::read(@attributes['path']).first
-        @attributes['original'] = image_hash(@attributes['path'], img.columns, img.rows)
-        @attributes['resized'] = resize_image(img, config)
-        @attributes['template'] ||= config['template']
-
-        partial = File.read(@attributes['template'])
-        template = Liquid::Template.parse(partial)
-
-        template.render!(@attributes)
-      end
-    end
-  end
-end
+require 'jekyll/responsive_image/version'
+require 'jekyll/responsive_image/defaults'
+require 'jekyll/responsive_image/tag'
 
 Liquid::Template.register_tag('responsive_image', Jekyll::ResponsiveImage::Tag)
diff --git a/lib/jekyll/responsive_image/defaults.rb b/lib/jekyll/responsive_image/defaults.rb
new file mode 100644
index 0000000..94464f7
--- /dev/null
+++ b/lib/jekyll/responsive_image/defaults.rb
@@ -0,0 +1,13 @@
+module Jekyll
+  class ResponsiveImage
+    @defaults = {
+      'default_quality' => 85,
+      'output_dir' => 'assets/resized',
+      'sizes' => [],
+    }.freeze
+
+    class << self
+      attr_reader :defaults
+    end
+  end
+end
diff --git a/lib/jekyll/responsive_image/tag.rb b/lib/jekyll/responsive_image/tag.rb
new file mode 100644
index 0000000..0d2cfd8
--- /dev/null
+++ b/lib/jekyll/responsive_image/tag.rb
@@ -0,0 +1,95 @@
+module Jekyll
+  class ResponsiveImage
+    class Tag < Liquid::Tag
+      def initialize(tag_name, markup, tokens)
+        super
+
+        @attributes = {}
+        @markup = markup
+
+        @markup.scan(::Liquid::TagAttributes) do |key, value|
+          # Strip quotes from around attribute values
+          @attributes[key] = value.gsub(/^['"]|['"]$/, '')
+        end
+      end
+
+      def resize_image(img, config)
+        output_dir = config['output_dir']
+        ensure_output_dir_exists!(output_dir)
+
+        resized = []
+
+        config['sizes'].each do |size|
+          width = size['width']
+          ratio = width.to_f / img.columns.to_f
+          height = (img.rows.to_f * ratio).round
+
+          filename = resized_filename(img.filename, width, height)
+          filepath = "#{output_dir}/#{filename}"
+
+          next unless needs_resizing?(img, width)
+
+          resized.push(image_hash(filepath, width, height))
+
+          # Don't resize images more than once
+          next if File.exists?(filepath)
+
+          Jekyll.logger.info "Generating #{filepath}"
+
+          i = img.scale(ratio)
+          i.write(filepath) do |f|
+            f.quality = size['quality'] || config['default_quality']
+          end
+
+          i.destroy!
+        end
+
+        resized
+      end
+
+      # Insert resize information into a file path
+      #
+      #   resized_filename(/foo/bar/file.name.jpg, 500, 300)
+      #     => /foo/bar/file.name-500x300.jpg
+      #
+      def resized_filename(path, width, height)
+        File.basename(path).sub(/\.([^.]+)$/, "-#{width}x#{height}.\\1")
+      end
+
+      def needs_resizing?(img, width)
+        img.columns > width
+      end
+
+      def ensure_output_dir_exists!(dir)
+        unless Dir.exists?(dir)
+          Jekyll.logger.info "Creating output directory #{dir}"
+          Dir.mkdir(dir)
+        end
+      end
+
+      # Build a hash containing image information
+      def image_hash(path, width, height)
+        {
+          'path'   => path,
+          'width'  => width,
+          'height' => height,
+        }
+      end
+
+      def render(context)
+        config = ResponsiveImage.defaults.dup
+        config.merge!(context.registers[:site].config['responsive_image'])
+
+        img = Magick::Image::read(@attributes['path']).first
+        @attributes['original'] = image_hash(@attributes['path'], img.columns, img.rows)
+        @attributes['resized'] = resize_image(img, config)
+        @attributes['template'] ||= config['template']
+
+        partial = File.read(@attributes['template'])
+        template = Liquid::Template.parse(partial)
+
+        template.render!(@attributes)
+      end
+    end
+  end
+end