Merging PDFs

sample_code.rb

# ************************************************************************************************
# *** Mergin with ghostscript
# ************************************************************************************************
GhostScript = `which gs`.chomp
 
dir    = Rails.root.join('tmp').to_s
 
file_names = [
  '2013_01_24_Pfandhalterschaft_DE.pdf',
  '2013_01_24_Passivitaetserklaerung_DE.pdf',
  '2013_01_24_Pfandhalterschaft_DE.pdf',
]

# @return [String]
#   The binary …
def merge_pdfs(files)
  ro,wo = IO.pipe
  re,we = IO.pipe
  spawn(GhostScript, '-dBATCH', '-dNOPAUSE', '-q', '-sDEVICE=pdfwrite', '-sOUTPUTFILE=-', *files, out: wo, err: we)
  wo.close
  we.close
 
  ro.read
end

files = file_names.map { |file_name| "#{dir}/#{file_name}" }
merged_pdf = merge_pdfs(files)

File.open('merged.pdf', 'w') {|f| f.write(merged_pdf) }



# ************************************************************************************************
# *** Mwergin with Prawn
# ************************************************************************************************

bundle     = HappyPackage::Bundle.for(bundle_key)
bundle_pdf = Service::Pdf::Merge.new(bundle.file_paths(locale))

bundle_pdf.to_pdf

# service ----------------------------------------------------------------------------------------
require 'prawn'

# Merges multiple pdfs into one pdf
class Service::Pdf::Merge
  # @param [Array] Absolute paths of the pdfs. For multipage pdf pass an array with pagecount and the path.
  def initialize(pdfs=[])
    @pdfs = pdfs.map {|e| e.is_a?(Array) ? (e if File.file?(e[1])) : ([1, e] if File.file?(e)) }.compact
  end

  # Renders the pdfs to one pdf.
  #
  # @return [String] PDF
  def to_pdf
    raise 'No pdf paths defined' if @pdfs.empty?

    pdf          = Prawn::Document.new template: @pdfs[0][1]
    current_page = @pdfs[0][0]

    pdf.go_to_page current_page

    @pdfs[1..-1].each do |page|
      pdf.start_new_page template: page[1]
      current_page += page[0]
      pdf.go_to_page current_page
    end if @pdfs.count > 1

    pdf.render
  end
end