Alexey Boroda / total-automation

  /*
  Plugin: jQuery Parallax
  Version 1.1.3
  Author: Ian Lunn
  Twitter: @IanLunn
  Author URL: http://www.ianlunn.co.uk/
  Plugin URL: http://www.ianlunn.co.uk/plugins/jquery-parallax/
  
  Dual licensed under the MIT and GPL licenses:
  http://www.opensource.org/licenses/mit-license.php
  http://www.gnu.org/licenses/gpl.html
  */
  

  (function( $ ){
  	var $window = $(window);
  	var windowHeight = $window.height();

  	$window.resize(function () {
  		windowHeight = $window.height();
  	});

  	$.fn.parallax = function(xpos, speedFactor, outerHeight) {
  		var $this = $(this);
  		var getHeight;
  		var firstTop;
  		var paddingTop = 0;
  		
  		//get the starting position of each element to have parallax applied to it		
  		$this.each(function(){
  		    firstTop = $this.offset().top;
  		});

  		if (outerHeight) {
  			getHeight = function(jqo) {
  				return jqo.outerHeight(true);
  			};
  		} else {
  			getHeight = function(jqo) {
  				return jqo.height();
  			};
  		}
  			
  		// setup defaults if arguments aren't specified
  		if (arguments.length < 1 || xpos === null) xpos = "50%";
  		if (arguments.length < 2 || speedFactor === null) speedFactor = 0.1;
  		if (arguments.length < 3 || outerHeight === null) outerHeight = true;
  		
  		// function to be called whenever the window is scrolled or resized
  		function update(){
  			var pos = $window.scrollTop();				

  			$this.each(function(){
  				var $element = $(this);
  				var top = $element.offset().top;
  				var height = getHeight($element);

  				// Check if totally above or totally below viewport
  				if (top + height < pos || top > pos + windowHeight) {
  					return;
  				}

  				$this.css('backgroundPosition', xpos + " " + Math.round((firstTop - pos) * speedFactor) + "px");
  			});
  		}		

  		$window.bind('scroll', update).resize(update);
  		update();
  	};

  })(jQuery);