Rakefile - take a source PDF of pages and spit out a printer-ready version for binding as a 8.5x5.5" book

yuckybind.rb

require 'colored'

def x(message)
	puts 'x '.red << message
	abort
end

def √(message)
	puts '√ '.green << message
end

def status(message)
	puts '- '.cyan << message
end

task :default, [:input_pdf, :signature_count] => :clean do |task, args|

	args = args.with_defaults \
		input_pdf: 'yucky.pdf',
		signature_count: 9
	input_pdf = args[:input_pdf]
	signature_count = args[:signature_count]

	# count pages in input pdf
	input_length = `pdftk "#{input_pdf}" dump_data | grep ^PageMediaNumber | wc -l`.to_i

	# TODO: shouldn't REALLY have to be perfectly divisible,
	# because you can always have signatures of different lengths.
	x "Number of pages in input PDF must be divisible by both signature_count (i.e. #{signature_count}) and 4" unless input_length % (signature_count * 4) === 0

	# determine length of each signature
	signature_length = input_length / signature_count

	status "building #{signature_count} signatures of #{signature_length} pages (#{signature_length/4} sheets) each"

	mkdir_p 'sig'

	# create signatures
	signature_count.times do |i|

		status "creating signature ##{i}"

		# create new human-ordered pdf for this signature
		first_page = (i * signature_length) + 1
		last_page = first_page + signature_length - 1
		sh "pdftk Y=\"#{input_pdf}\" cat Y#{first_page}-#{last_page} output sig/#{i}.pdf"

		# collate
		middle = signature_length / 2
		sh "pdftk S=sig/#{i}.pdf shuffle Send-#{middle+1}even S1-#{middle}odd S1-#{middle}even Send-#{middle+1}odd output sig/#{i}_coll.pdf"

		# create n-up version
		sh "pdfnup --papersize '{8.5in,11in}' sig/#{i}_coll.pdf -o sig/#{i}_nup.pdf"

		√ "#{i}_nup.pdf"

	end

	√ "all signatures created"

	# join 'em back together
	status "putting it all together..."

	sh "pdftk sig/*_nup.pdf cat output yucky_nup.pdf"

	√ 'yucky_nup.pdf ' << "(#{signature_count} signatures of #{signature_length/4} sheets each)".green

end

task :clean do
	rm_rf 'yucky_nup.pdf'
	rm_rf 'sig/'
end