title: Drawing a opacity radial gradient on a HTML canvas and use it as a background
body: <p>I'm looking for a way to make a canvas object look like this: <a href="http://www.onetuts.com/attachments/2010/05/07/1_201005072156152XYem.jpg" rel="nofollow">http://www.onetuts.com/attachments/2010/05/07/1_201005072156152XYem.jpg</a></p>
  
  <p>The gradient should be going from rgba(0,0,0,0.8) to rgba(0,0,0,0.2) but i don't get the canvas to be 1280x720px.</p>