Team:Tongji Shanghai/js/jquery.parallax.js

/* 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

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(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);