title: ImageMagick: put white background under transparent PNG, then invert colors
body: <p>I have a PNG image with a black shape on transparent background.
  I need a white shape on a solid black background instead.</p>
  
  <p>How can I achieve that with Imagemagick?</p>
  
  <p>Image example:</p>
  
  <p><strong>I have this:</strong></p>
  
  <p><a href="https://i.stack.imgur.com/5qdbk.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/5qdbk.png" alt="enter image description here"></a></p>
  
  <p><strong>I want this:</strong></p>
  
  <p><a href="https://i.stack.imgur.com/XiOTe.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/XiOTe.png" alt="enter image description here"></a></p>