gistfile1.rb

# AR model callback that uses paperclip and tempfile

def generate_previews
    
    dimension_multiplier = case units
      when 'inches'; 30
      else; 30
      end
    
    png_width   = (self.width * dimension_multiplier).to_i
    png_height  = (self.height * dimension_multiplier).to_i
    
    tmp_svg = Tempfile.new('rsvg_svg', "#{RAILS_ROOT}/tmp")
    tmp_png = Tempfile.new('rsvg_png', "#{RAILS_ROOT}/tmp") 
    tmp_svg.write self.svg
    tmp_svg.flush
    
    # rsvg svg to png conversion
    system "#{RSVG_PATH} -d 72 -w #{png_width} -h #{png_height} #{tmp_svg.path} #{tmp_png.path}"
    
    # Paperclip call
    File.open(tmp_png.path) {|img| self.image = img}
    
    tmp_svg.close!
    tmp_png.close!
    
  end