https://www.boyerlutherie.com/wp-content/themes/wp_haswell/assets/js/jquery.parallax-1.1.3.js?ver=1.1.3

1/*
2Plugin: jQuery Parallax
3Version 1.1.3
4Author: Ian Lunn
5Twitter: @IanLunn
6Author URL: http://www.ianlunn.co.uk/
7Plugin URL: http://www.ianlunn.co.uk/plugins/jquery-parallax/
8Dual licensed under the MIT and GPL licenses:
9http://www.opensource.org/licenses/mit-license.php
10http://www.gnu.org/licenses/gpl.html
11*/
12
13(function( $ ){
14	var $window = $(window);
15	var windowHeight = $window.height();
16
17	$window.resize(function () {
18		windowHeight = $window.height();
19	});
20
21	$.fn.parallax = function(xpos, speedFactor, outerHeight) {
22		var $this = $(this);
23		var getHeight;
24		var firstTop;
25		var paddingTop = 0;
26		
27		//get the starting position of each element to have parallax applied to it		
28		$this.each(function(){
29		    firstTop = $this.offset().top;
30		});
31
32		if (outerHeight) {
33			getHeight = function(jqo) {
34				return jqo.outerHeight(true);
35			};
36		} else {
37			getHeight = function(jqo) {
38				return jqo.outerHeight();
39			};
40		}
41			
42		// setup defaults if arguments aren't specified
43		if (arguments.length < 1 || xpos === null) xpos = "50%";
44		if (arguments.length < 2 || speedFactor === null) speedFactor = 0.1;
45		if (arguments.length < 3 || outerHeight === null) outerHeight = true;
46		
47		// function to be called whenever the window is scrolled or resized
48		function update(){
49			var pos = $window.scrollTop();				
50
51			$this.each(function(){
52				var $element = $(this);
53				var top = $element.offset().top;
54				var height = getHeight($element);
55
56				// Check if totally above or totally below viewport
57				if (top + height < pos || top > pos + windowHeight) {
58					return;
59				}
60
61				$this.css('backgroundPosition', xpos + " " + Math.round((firstTop - pos) * speedFactor) + "px");
62			});
63		}		
64
65		$window.bind('scroll', update).resize(update);
66		update();
67	};
68})(jQuery);