CSS box shadow around triangle
http://stackoverflow.com/questions/5332366
by Marcel
HTML
<canvas id="triangle" width="100" height="100">
<img src="fallback-triange.png" alt="A triangle">
</canvas>
JavaScript
var t_can = document.getElementById("triangle");
if (t_can.getContext) {
var t_con = t_can.getContext('2d');
t_con.fillStyle = "#000";
t_con.shadowBlur = 10;
t_con.shadowColor = "#000";
// Draw a triangle
t_con.beginPath();
t_con.moveTo(20, 20);
t_con.lineTo(20, 80);
t_con.lineTo(80, 20);
t_con.lineTo(20, 20);
t_con.fill();
t_con.closePath();
}