title: How to work Cache of media/catalog/product/cache in Magento
body: <p>i want to know how to work the cache of media/catalog/product/cache i don´t know how made the directory structure. 
  My example is </p>
  
  <pre><code>media\catalog\product\cache
  
    \1\small_image\120x120\9df78dab3d52sd08dse5fw8d27w36e95
  
        a\
        b\
        d\
        ...
  </code></pre>
  
  <p>i don´t understand how to take the number 1 in cache\
  next how to take the hash key 9df78dab3d52sd08dse5fw8d27w36e95
  and many times in stead of higthxweith(directory) take numberx(directory)
  I need to know all because i want to made a external CDN and liberate to resize images in my machine.
  Thx</p>