PhantomJS screenshots

/*
 Use:
 phantomjs render.js 1024x768 http://gasteroprod.com/
 */

var args = require('system').args,
    url = 'http://www.google.com/',
        now = new Date(),
    nowString = now.getFullYear() + pad(now.getMonth() + 1) + pad(now.getDate()) + '-' + pad(now.getHours()) + pad(now.getMinutes()) + pad(now.getSeconds()),
    viewportSize = {width: 1280, height: 1024},
    page = require('webpage').create();

if (args.length >= 1) {
  args.forEach(function(arg, i) {
    // set URL
    if (arg.match(/^https?:\/\//)) {
      url = arg;
    }
    // set viewport size
    if (arg.match(/^[0-9]+x[0-9]+$/)) {
            var viewportParts = arg.split('x');
            viewportSize = {width: viewportParts[0], height: viewportParts[1]};
    }
  });
}
console.log('Url: ' + url);
console.log('Viewport: width=' + viewportSize.width + ' / height=' + viewportSize.height);
page.viewportSize = viewportSize;
page.clipRect = {
  top: 0,
  left: 0,
  width: viewportSize.width,
  height: viewportSize.height
};
var screenshotPath = 'screenshots/' + nowString + '-' + viewportSize.width + 'x' + viewportSize.height + '/screenshot-';

// launch timer
var timer = Date.now();

// open the page and kill phantom upon completion
page.open(url, function (status) {
  phantom.exit();
});

// try to get a screenshot every 10 milliseconds
setInterval(function() {
  page.render(screenshotPath + pad(Date.now() - timer, 6) + '.png');
}, 10);

// 30 seconds timeout
setTimeout(function() {
  phantom.exit();
}, 30000);


function pad(number, size) {
  var r = String(number);
  while (r.length < size) {
    r = '0' + r;
  }
  return r;
}