Repack ePubs that can not show a correct cover image in iTunes and iBooks for iOS.

repack_epub.rb

#!/usr/bin/env ruby
require "fileutils"
include FileUtils

ERROR = 255

def repack(book, tmpdir)
  book_name = File.basename(book, ".epub")
  system(%|unzip "#{book}" -d #{tmpdir} > /dev/null 2>&1|)
  cd(tmpdir) do
    dirs = Dir["*"].delete_if {|f| !File.directory?(f) }
    # If no directory found! Just stop repack.
    if dirs.size == 0
      puts "\nFailed to repack \"#{book}\": Unknown Error!!!"
      return ERROR
    end
    # If more than one directory found.
    if dirs.size > 2
      puts "\nFailed to repack \"#{book}\": Ambiguious ePub file structure."
      return ERROR
    end
    dirs.delete("META-INF");dirs.delete("meta-inf") # delete the meta-inf.
    cd dirs[0] do
      covers = Dir["*"].delete_if{ |f| !f.match(/.*cover.*\.(jpg|png|gif)/i) }
      if covers.size == 0
        # If no cover found in root directory, try image directory.
        image_dir = Dir["*"].delete_if{ |f| !(f.match(/image|img/i) && File.directory?(f))}[0]
        if image_dir.size == 0
          puts "\nFailed to repack \"#{book}\": Image directory not found."
          return ERROR
        else
          covers = Dir["#{image_dir}/*"].delete_if { |f| !f.match(/.*cover.*\.(jpg|png|gif)/i) }
          if covers.size == 0
            puts "\nFailed to repack \"#{book}\": Cover Image not found."
            return ERROR
          end
        end
      end
      if covers.size == 0
        puts "\nFailed to repack \"#{book}\": Cover Image not found."
        return ERROR
      end
      cover = covers[0] # Just pick up the first one as cover.
      cp cover, "../iTunesArtwork"
    end
    # Back to tmpdir and repack
    system(%|zip -Xr9D ../"#{book_name}_repack.epub" mimetype * > /dev/null 2>&1|)
  end
  rm_rf(tmpdir)
end

# Do the repack
books = ARGV.size < 1 ? Dir["*.epub"] : ARGV
if books.size < 1
  puts "No ePub files found!"
  exit 1
end

books.each do |b|
  tmpdir = "tmpdir_#{Time.now.to_i}"
  print %|Processing "#{b}"...|
  if repack(b, tmpdir) != ERROR
    puts "Done!"
  else
    rm_rf(tmpdir)
  end
end