listen_uploads.rb

#!/usr/bin/env ruby

require 'listen'
require 'skeptick'
require 'pp'

include Skeptick

uploads_dir = "/u/files/"
originals = "uploads/"

sizes = {
  "small" => {
    "location" => "small/",
    "size" => "300x"
  },
  "medium" => {
    "location" => "med/",
    "size" => "600x"
  },
  "web" => {
    "location" => "web/",
    "size" => "900x"
  }
}

listener = Listen.to(uploads_dir+originals) do |added|
  sizes.each { |size,data|
    if (added[0] != nil)
      addfile = File.basename(added[0])
      from = uploads_dir+originals+addfile
      to = uploads_dir+data["location"]+addfile
      make = convert(from, to: to) do
        set :scale, data["size"]
      end
      make.run
    end
   }
end
listener.start # not blocking
sleep