base.rb

      def material_pictograms_for_region(region)
        return "" unless material.pictograms_of(region).present?
        hazard_pictograms = []
        pictograms_path = Rails.root.join("app/assets/images/hazard-pictograms/")
        image_names = Dir[pictograms_path + "*.png"].map { |f| f.split("/").last }
        image_names.map! {|n| File.basename(n,File.extname(n)) } # remove png extension
        image_names = image_names.sort.reverse # so that we select latest coincidence
        material.pictograms_of(region).map { |pic|
          pic.image_name if pic.image_name.present?
        }.compact.map { |pictogram_name|
          image_names.detect { |name| Regexp.new(name).match(pictogram_name) }
        }.compact.each { |image_name|
          path = Rails.root.join("app/assets/images/hazard-pictograms/" + image_name + ".png")
          hazard_pictograms << Base64.encode64(open(path) { |io| io.read })
        }
        hazard_pictograms.map do |pictogram|
        {
           region + "-pictogram.image" => pictogram
        }
        end
      end