title: Add shadow to Canvas element (keeping the element transparent)
body: <p>I have a circle shape in my HTML5 canvas. I'd like to give it a shadow style but without showing the stoke, so stoke should be 0 and shadow: visible.</p>
  
  <p>Here is my code:</p>
  
  <pre><code>context.beginPath();
  context.lineWidth = 5;
  context.shadowColor = 'black';
  context.strokeStyle = "rgba(255,0,0,1)";
  context.shadowBlur = 10;
  context.shadowOffsetX = 0;
  context.shadowOffsetY = 0;
  context.arc(x, y, 45, 0, 2 * Math.PI, false);
  context.stroke();
  context.restore();
  context.save();
  </code></pre>
  
  <p>I found a similar method online but it does not work an honestly I dont understand it.</p>
  
  <pre><code>context.beginPath();
  context.lineWidth = 10;
  RGraph.setShadow({'context': context}, 'black', 0, 0, 15)
  context.arc(mouseXY[0], mouseXY[1], radius + 5, 0, 2 * Math.PI, false);
  context.stroke();
  </code></pre>
  
  <p>Any Idea to make to have a shadow for an invisible shape ?</p>