Balanced image directories

# Make balanced image directories to improve file system search
#
# Example:
#
# make_balanced_dirs(2, 4)
# ac3294f2b0174ee1.jpg -> ac329/4f2b/ac3294f2b0174ee1.jpg
#

def make_balanced_dirs levels, length
  Dir.glob("*.jpg").collect do |f|
    f.split('.')[0].gsub(/[a-f0-9]{lenght}/) { |m| File.join(m,'') }[0..(levels*length)+1].concat(f)
  end
end