glitchy.rb

filename = "test.jpg"
size = File.size(filename)
count = %x{wc -l #{filename}}.split.first.to_i
factor = count/300
factor = 1 if factor < 1


File.open(filename, "rb+") do |file|
  # skip some
  file.seek(size/(rand(10..20)), IO::SEEK_CUR)
  file.each_line do |line|
    puts line
    if rand(rand(3..5)*factor) == 0
      line_arr = line.force_encoding("ASCII-8BIT").split("")
      line_arr[rand(line_arr.length)] = rand(256).chr
      new_line = line_arr.join()
      file.seek(-(new_line.length), IO::SEEK_CUR)
      file.write(new_line)
    end
  end
end