create a hovering image that displays the contents of an HTML5 canvas

debug-canvas-image.js

(function () {
  var img = document.createElement('img');
  document.body.appendChild(img);
  img.style.position = 'fixed';
  img.style.top = 0;
  img.style.right = 0;
  img.style.width = '500px';
  img.style.background = '#fff';
  img.style['z-index'] = 1000000;
  window.addEventListener('keypress', function (e) {
    // "s" is for "snapshot"
    if (e.keyCode === 115)
      img.src = canvas.toDataURL();
  });
}());