title: Export canvas to image?
body: <p>I'm making a facebook app. It will get image of user from "<a href="https://graph.facebook.com/" rel="nofollow">https://graph.facebook.com/</a>{fbid}/picture". Then I draw that image to a canvas.
  It worked well. But when I export that canvas to base64 image, it return error: </p>
  
  <blockquote>
    <p>Failed to execute 'toDataURL' on 'HTMLCanvasElement': Tainted canvases may not be exported.</p>
  </blockquote>
  
  <p>I tried to set crossOrigin = "anonymous" for each image before draw it to canvas. Then it worked well with chrome browser.</p>
  
  <p>But on safari, it return error:</p>
  
  <blockquote>
    <p>Cross-origin image load denied by Cross-Origin Resource Sharing policy.</p>
  </blockquote>
  
  <p>Can anyone please help me?</p>