added png to image-src.js example

examples/image-src.js

@@ -32,6 +32,11 @@ ctx.drawImage(img, 0, 0, 50, 50);
 ctx.drawImage(img, 50, 0, 50, 50);
 ctx.drawImage(img, 100, 0, 50, 50);
 
+var squid = fs.readFileSync(__dirname + '/images/squid.png');
+img = new Image;
+img.src = squid;
+ctx.drawImage(img, 50, 50, 50, 50);
+
 var out = fs.createWriteStream(__dirname + '/image-src.png')
   , stream = canvas.createPNGStream();