65 lines
2.4 KiB
JavaScript
65 lines
2.4 KiB
JavaScript
var Parallax = {
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initialise: function(createEvents) {
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$(this.ident).each(function(){
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// Calculate Offset
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inset = $(this).attr('parallax-inset');
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image_height = $(this).height();
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range = image_height / inset;
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$(this).attr('parallax-offset', range / 2);
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});
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console.log("Parallax Initialised.");
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if (createEvents) {this.createEvents();}
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this.calculate();
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},
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calculate: function() {
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window_top = $(window).scrollTop();
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window_bottom = window_top + $(window).height();
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$(this.ident).each(function(){
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if (!is_on_screen(this) || !$(this).attr('parallax-offset') != false) { return; }
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element = $(this);
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center_pos = (element.offset().top - $(window).scrollTop()) + (element.height() / 2);
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perc = -(0.5 - ((window_top - center_pos) / window_bottom));
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pos = Math.round((perc * element.attr('parallax-offset')) * 100) / 100;
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element.css('background-position',"0px " + pos + "px");
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});
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},
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createEvents: function() {
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$(window).scroll(function() { Parallax.calculate(); });
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$(window).resize(function() { Parallax.initialise(); })
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},
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ident: '.parallax'
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}
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function is_on_screen(elm) {
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var vpH = $(window).height(),
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st = $(window).scrollTop(),
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y = $(elm).offset().top,
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elementHeight = $(elm).height();
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return ((y < (vpH + st)) && (y > (st - elementHeight)));
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}
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function init_parallax() {
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$('.parallax').each(function(){
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// Calculate Offset
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inset = $(this).attr('parallax-inset');
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image_height = $(this).height();
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range = image_height / inset;
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$(this).attr('parallax-offset', range / 2);
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});
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console.log("Parallax Initialised.");
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parallax();
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}
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function parallax() {
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window_top = $(window).scrollTop();
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window_bottom = window_top + $(window).height();
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$('.parallax').each(function(){
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if (!is_on_screen(this) || !$(this).attr('parallax-offset') != false) { return; }
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element = $(this);
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center_pos = (element.offset().top - $(window).scrollTop()) + (element.height() / 2);
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perc = -(0.5 - ((window_top - center_pos) / window_bottom));
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pos = Math.round((perc * element.attr('parallax-offset')) * 100) / 100;
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element.css('background-position',"0px " + pos + "px");
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});
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}
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