JSFiddle - React, Tailwind, and code Playground

HTML

<canvas id="canvas1" width="500" height="500"></canvas>

JavaScript

var can = document.getElementById('canvas1');
var ctx = can.getContext('2d');


ctx.fillRect(50,50,50,50); // something in the background

var img = new Image();
img.onload = function() {
    ctx.drawImage(img, 0, 0);
}
  img.src = "http://upload.wikimedia.org/wikipedia/commons/thumb/4/47/PNG_transparency_demonstration_1.png/280px-PNG_transparency_demonstration_1.png"; //transparent png