current_track.rb

#!/usr/bin/env ruby

require "osx/cocoa"
require "erb"
require "base64"
include OSX

def pict_bytes_for(artwork)
  image_rep = artwork.data.representations.first
  data      = image_rep.PICTRepresentation

  bytestr = "\0"*512 + data.bytes.bytestr(data.length)
  Base64.encode64 bytestr
end

require_framework "ScriptingBridge"

itunes = SBApplication.applicationWithBundleIdentifier 'com.apple.iTunes'
track  = itunes.currentTrack

puts ERB.new(DATA.read, 0, "%-<>").result(binding)

__END__
<?xml version="1.0" encoding="UTF-8"?>
<track>
  <name><%= track.name %></name>
  <artist><%= track.artist %></artist>
  <album><%= track.album %></album>
  <artworks>
    <% track.artworks.each do |artwork| %>
    <artwork><%= pict_bytes_for artwork %></artwork>
    <% end %>
  </artworks>
</track>