title: Can someone please explain clearly how to use "pngcrush" for multiply items
body: <p>I have a stack of hundreds of pictures and i want to use pngcrush for reducing the file sizes.</p>
  
  <p>I know how to crush one file with terminal, but all over the web i find parts of explanations that assume previous knowledge.</p>
  
  <p>can someone please explain how to do it clearly.</p>
  
  <p>Thanks
  Shani</p>