Merge decorator with original file from spree

app/models/spree/image.rb

@@ -46,5 +46,27 @@ module Spree
         false
       end
     end
+
+    # Spree stores attachent definitions in JSON. This converts the style name and format to
+    # strings. However, when paperclip encounters these, it doesn't recognise the format.
+    # Here we solve that problem by converting format and style name to symbols.
+    # See also: ImageSettingsController decorator.
+    #
+    # eg. {'mini' => ['48x48>', 'png']} is converted to {mini: ['48x48>', :png]}
+    def self.format_styles(styles)
+      styles_a = styles.map do |name, style|
+        style[1] = style[1].to_sym if style.is_a? Array
+        [name.to_sym, style]
+      end
+
+      Hash[styles_a]
+    end
+
+    def self.reformat_styles
+      Spree::Image.attachment_definitions[:attachment][:styles] =
+        format_styles(Spree::Image.attachment_definitions[:attachment][:styles])
+    end
+
+    reformat_styles
   end
 end

app/models/spree/image_decorator.rb

@@ -1,23 +0,0 @@
-Spree::Image.class_eval do
-  # Spree stores attachent definitions in JSON. This converts the style name and format to
-  # strings. However, when paperclip encounters these, it doesn't recognise the format.
-  # Here we solve that problem by converting format and style name to symbols.
-  # See also: ImageSettingsController decorator.
-  #
-  # eg. {'mini' => ['48x48>', 'png']} is converted to {mini: ['48x48>', :png]}
-  def self.format_styles(styles)
-    styles_a = styles.map do |name, style|
-      style[1] = style[1].to_sym if style.is_a? Array
-      [name.to_sym, style]
-    end
-
-    Hash[styles_a]
-  end
-
-  def self.reformat_styles
-    Spree::Image.attachment_definitions[:attachment][:styles] =
-      format_styles(Spree::Image.attachment_definitions[:attachment][:styles])
-  end
-
-  reformat_styles
-end