class ActiveStorage::Previewer::PDFPreviewer

def self.accept?(blob)
  blob.content_type == "application/pdf"
end

def preview
  download_blob_to_tempfile do |input|
    draw "mutool", "draw", "-F", "png", "-o", "-", input.path, "1" do |output|
      yield io: output, filename: "#{blob.filename.base}.png", content_type: "image/png"
    end
  end
end