iruby_plantuml.rb

class Plantuml < SimpleDelegator
end

module IRuby
  module Display
    module Registry
      type { Plantuml }
      format 'image/svg+xml' do |obj|
        Tempfile.open('uml') do |uml|
          uml.write(obj)
          uml.flush
          Tempfile.open('svg') do |svg|
            `plantuml -p -tsvg < #{uml.path} > #{svg.path}`
            svg.read
          end
        end
      end
    end
  end
end