Make a canvas, then convert it to an image

1.html

<canvas id="viewport"></canvas>

<script>
  var canvas = document.getElementById('viewport');
  var context = canvas.getContext('2d');

  make_base();

  var img = canvas.toDataURL("image/png");

  document.write('<img src="'+img+'"/>');

  function make_base(){
    var base_image = new Image();
    base_image.src = '/assets/thumbL/52.png';
    base_image.onload = function(){
      context.drawImage(base_image, 0, 0);
    }
  }
</script>