title: HTML5 canvas: only outer shadow
body: <p>If I draw a rectangle to the canvas, and I enable the shadows, then there will be created inner, and outer shadows too, but I only want outer shadow.</p>
  
  <pre><code>var c=document.getElementById("myCanvas");
  var ctx=c.getContext("2d");
  
  ctx.shadowColor = 'black';
  ctx.shadowBlur = 5;
  
  ctx.strokeRect(20,30,150,75);
  </code></pre>
  
  <p>The only way I've found is <code>ctx.clearRect(20,30,150,75);</code>. But it's not really what I want, because there  may be something under my rect, and I don't want to delete it.</p>
  
  <p>Thanks in advance,</p>