<!DOCTYPE HTML>
<html>
<body>
<canvas moz-opaque id="c" width="500" height="500"></canvas>
<script>
var ctx = c.getContext('2d');
ctx.fillStyle = "white";
ctx.fillRect(0, 0, 500, 500);
ctx.fillStyle = "black";
ctx.font = "50px sans-serif";
ctx.fillText("Hello", 200, 200);
</script>
</body>
</html>