Improvement of Rubella::Output::Image

The class now overwrites the constructor of the basic class to set a default
field_size value of 15 pixels.
It also returns self in the create method corresponding to the base class.
Plus I've added the documentation.

lib/rubella/output/base.rb

@@ -17,6 +17,7 @@ module Rubella
       #
       # @param field_size int size of one value
       # @return Rubella::Output::Base
+      #
       def initialize field_size
         @field_size = field_size
       end
@@ -26,6 +27,7 @@ module Rubella
       #
       # @param storage Rubella::Storage
       # @return Rubella::Output::Base
+      #
       def create storage
         raise NotImplementedError "Please override 'create' in your concrete "+
           "implementation"

lib/rubella/output/image.rb

@@ -4,8 +4,29 @@ require 'RMagick'
 module Rubella
   module Output
 
+    # Creates a pixel based graphic as representation of the given storage
+    # data using ImageMagick.
+    # By the RMagick extention. @data will contain a Magick image for futher
+    # handling the data please read the RMagick library documentation:
+    # http://www.imagemagick.org/RMagick/doc/
+    #
     class Image < Base
 
+      # Constructor
+      # Has a default field_size of 15 pixel.
+      #
+      # @param field_size int How many pixel one value has
+      # @return Rubella::Output::Image
+      #
+      def initialize field_size = 15
+        super field_size
+      end
+
+      # Creates a pixel based graphic from the given storage data.
+      #
+      # @param storage Rubella::Storage
+      # @return Rubella::Output::Image
+      #
       def create storage
         buckets = storage.data[0].length
         columns = storage.data.length
@@ -15,7 +36,7 @@ module Rubella
         y = buckets*@field_size
 
         # start drawing the damn thing
-        loadImg = Magick::Image.new(x, y) { self.background_color = "white" }
+        @data = Magick::Image.new(x, y) { self.background_color = "white" }
 
         i = 0
         storage.data.each do |point|
@@ -34,13 +55,13 @@ module Rubella
             # Draw
             core.fill(Magick::Pixel.from_hsla(0, 255, l, 1).to_color)
             core.rectangle((i*@field_size), (j*@field_size), ((i+1)*@field_size), ((j+1)*@field_size))
-            core.draw loadImg
+            core.draw @data
             j = j + 1
           end
           i = i + 1
         end
 
-        @data = loadImg
+        self
       end