title: Custom google maps marker from sprite and retina proof
body: <p>I've learnt that when I would like to use sprites as google Map markers, I need to put it like this:</p>
  
  <pre><code>var myIcon = new google.maps.MarkerImage(
      "../public/img/categories.png",
      new google.maps.Size(90, 50),
      new google.maps.Point(0, data[i].subcategory_id * 50)
  );
  
  // as I understand: 
  // new google.maps.MarkerImage(url, original size, anchor point);
  </code></pre>
  
  <p>when making it retina-proof, I understand I need to make it like this:</p>
  
  <pre><code>//new google.maps.MarkerImage(url, original size, anchor point, null, half size);
  var myIcon = new google.maps.MarkerImage(
      "../public/img/categories.png",
      new google.maps.Size(90,50),
      new google.maps.Point(0, data[i].subcategory_id * 50),
      null,
      new google.maps.Size(45,25)
  );
  </code></pre>
  
  <p>However, when adding the extra size, my marker isn't there anymore.
  What am I doing wrong?</p>