HTML5 CSS3下雪奥运五环背景动画特效

代码片段：

var generateCanvasImageUrl = function generateCanvasImageUrl() {
  var _window = window,
      innerHeight = _window.innerHeight,
      innerWidth = _window.innerWidth;
  var pixels = innerHeight / 1 * (innerWidth / 1);
  var $canvas = document.createElement('canvas');
  var context = $canvas.getContext('2d');
  $canvas.height = innerHeight / 1;
  $canvas.width = innerWidth / 1;
  for (var pixel = 0; pixel < pixels; pixel++) {
    var x = pixel % innerWidth;
    var y = Math.floor(pixel / innerWidth);
    var size = Math.floor(Math.random() * 3 + 1);
    context.fillStyle = '#fff';
    if (Math.random() > 0.9999) context.fillRect(x, y, size, size);
  }
  return $canvas.toDataURL();
};