Question

I need a simple jquery solution to add a background image to my page filling it entirely, but keeping the aspect ratio and vertical and horizontal centered position.

there are several plugins out here but I don’t want to use any plugin.

thanks in advance.

Answer 1

This code will do what you want..

$(function(){

    var stretcher = $('#background-container > img'),
        element = stretcher[0],
        currentSize = { width: 0, height: 0 },
        $document = $(document);

    $(window).resize(function () {
        var w = $document.width();
        var h = $document.height();

        if (currentSize.width != w || currentSize.height != h) {
            stretcher.width(w).height('auto');
            if (h > element.height) {
                stretcher.width('auto').height(h);
            }
            currentSize.width = w;
            currentSize.height = element.width;
        }
    })

    $(window).load(function () {
        $(this).trigger('resize');
    });

});

Set your HTML like this

<div id="page">
    Your page contents here..
</div>
<div id="background-container">
      <img src="path/to/image" />
</div>

and your CSS like

#background-container{
    position:absolute;
    z-index:1;
    top:0;
    left:0;
    width:100%;
    height:100%;
    overflow:hidden;
}

#page{
    position:relative;
    z-index:5;
}

Demo at http://jsfiddle.net/gaby/3YLQf/