title: Antialiasing shapes in Pygame
body: <p>I'm using Pygame to draw some things. The problem is that they have a lot of aliased edges:</p>
  
  <p><img src="https://i.stack.imgur.com/Tujj0.png" alt="Aliased concentric circles"></p>
  
  <p>I want to make them softer, like this:</p>
  
  <p><img src="https://i.stack.imgur.com/0K8UR.png" alt="Smooth concentric circles"></p>
  
  <hr>
  
  <p>My idea so far was to draw the shape in double size, and then use </p>
  
  <pre><code>pygame.transform.smoothscale(surf, (w/2, h/2))
  </code></pre>
  
  <p>to shrink it to the size I want.</p>
  
  <p>Unfortunately if I'm drawing my shapes on a transparent surface, the smoothscale turns the edges that were touching transparent pixels black!</p>
  
  <ul>
  <li>How do I smoothscale a picture without turning alpha-transparent pixels into black, or</li>
  <li>How else do I antialias edges?</li>
  </ul>