title: How to convert all files (in different formats) in given folder to different file type
body: <p>I have a folder with many images from different types (png, jpg, jpeg, bmp, pdf), and I would like to convert them all into png (for instance) using imagemagick.</p>
  
  <p>Is there a single command which can perform this? If not, what should I do instead?</p>
  
  <p>Thanks.</p>