title: How to convert PixelList to mask?
body: <p>I'm having a <code>PixelList</code> containing all set pixels of a binary mask. This looks the following: <code>PixelList: {[1447x2 int32]}</code>.</p>
  
  <p>How can I efficiently convert this <code>PixelList</code> do a binary mask with dimension <code>dim</code>?</p>
  
  <p>The trivial way would be:</p>
  
  <pre><code>mask = zeros(dim);
  for i=1:length(pixellist)
      mask(pixellist(i,2), pixellist(i,1)) = 1;
  end
  </code></pre>
  
  <p>But this is very slow. How to do that efficiently? </p>