ruby.rb

#!/usr/bin/env ruby -Ku

require 'rubygems'
require 'RMagick'
require 'digest/sha1'

Dir::glob("/home/foo/*.jpg").each do |f|

  original = Magick::Image.read(f).first
  resized = original.change_geometry("200x200") { |cols, rows| original.thumbnail(cols, rows) }
  if original.columns > original.rows 
    resized = resized.thumbnail(200,150)
  else
    resized = resized.thumbnail(100,150)
  end

  sha1 = Digest::SHA1.hexdigest(File.read(f))
  resized.write("/home/foo/thumbnail/#{sha1}.jpg")
end