title: Modify canvas from wasm
body: <p>Is it possible to efficiently modify the html5 canvas from web assembly?</p>
  
  <p>Update: </p>
  
  <pre><code>var imageData = context.getImageData(x, y, w, h)
  var buffer = imageData.data.buffer;  // ArrayBuffer
  </code></pre>
  
  <p>Could be the way if the buffer is writable.</p>