Issue with scruffy

Hi im trying to render a simple graph for the moment just to test the library but i'm having a problem... i try to run this example from other page.

graph = Scruffy::Graph.new     graph.title = "Favourite Snacks"     graph.renderer = Scruffy::Renderers::Pie.new

    graph.add :pie, '', {       'Apple' => 20,       'Banana' => 100,       'Orange' => 70,       'Taco' => 30     }

    graph.render :to => "pie_test.svg"     graph.render :width => 300, :height => 200,       :to => "pie_test.png", :as => 'png'

and i get an error in graph.render :width => 300, :height => 200, :to => "pie_test.png", :as => 'png'

no such file to load -- RMagick

i haven't found in any place something that says that scruffy needs rmagick to work... it's really necesary to install it for render the graph in a view?

I only ask because i'm having problems to install rmagick, it says that it failed building the native extencion even if i have installed the devkit