title: How to change the print size of an image in mm on command line?
body: <p>ImageMagick seems to be best to convert image files on the command line. However it only supports changing the size in pixels and the resolution in inch per pixel but not the <strong>print size</strong> (as shown with the command <code>identify -verbose</code>). I'd like to:</p>
  
  <ul>
  <li>quickly get the image print size in mm </li>
  <li>change the image print size (by setting either height or width or both to a new value in mm)</li>
  </ul>
  
  <p>This should be able with simple shell scripting, shouldn't it?</p>