pdf-reader.rb

def remove_blanks(filename)

  nonblank, ranges, range_first_val, range_last_val = [], [], 0, 0
  File.open(filename, "rb") do |io|
    reader = PDF::Reader.new(io)
    reader.pages.each_with_index do |page, i|
      nonblank << (i + 1) unless page.text.length.zero?
    end
    range_first_val, range_last_val = nonblank.first, nonblank.last
    range_first_val = -1 if nonblank.length === reader.pages.length
  end
  
  return filename if range_first_val === -1  # Keine leeren Seiten.
  return nil if nonblank.length.zero?        # Keine nicht-leeren Seiten.

  nonblank.each do |current_page_val|
    if current_page_val > range_last_val + 1
      ranges << "%s-%s" % [range_first_val, range_last_val]
      range_first_val = current_page_val
    end
    range_last_val = current_page_val
  end
  ranges << "%s-%s" % [range_first_val, range_last_val]
  
  puts ranges
  FileUtils.mv filename, filename + '.blanks.pdf'
  system("pdftk #{filename + '.blanks.pdf'} cat #{ranges.join(' ')} output #{filename}")
  filename

end

# usage remove_blanks("/home/fpuglisi/Downloads/orig.pdf")