Checks all JPEG's in a given folder and creates thumbnails for them

thumbnail_creator.rb

#!/usr/bin/env ruby
require 'RMagick'
include Magick

dir = ARGV[0].dup
dir << '/' unless dir.match(/\/$/)
thumbnails = Dir.pwd+"/"+dir+"thumbnails"
Dir.chdir(Dir.pwd+"/"+dir)
puts Dir.pwd
puts thumbnails
Dir.mkdir(thumbnails) unless File.exists?(thumbnails) && File.directory?(thumbnails)
Dir['*.jpg'].each do |name|
  puts name
  f = open(name)
  img = Image.from_blob(f.read).first
  f2 = open(thumbnails+"/"+name, "w")
  thumb = img.scale(ARGV[1].to_f/img.columns)
  f2.puts(thumb.to_blob)
  f.close
  f2.close
  puts name
end