title: SDWebImage process images before caching
body: <p>I fetch a lot of images from the web, and they are all kind of sizes - they can be big, small etc..</p>
  
  <p>So I can resize them when I display them in the cell but this is inefficient. It's way better to resize them after SDWebImage have download them and cache them resized, instead of storing large images on disk and resize them for every cell.</p>
  
  <p>So how can I do this with SDWebImage, or I have to hack a bit onto the class?</p>