Background Resize

ready.js

$(function(){
    var image = $('.background');
    function resize(){
        resizeBackground(image, 640, 480);
    }
    $(window).resize(resize);
});

resize.css

.background{ position:absolute; left:0; top:0; }
.full-width{ min-width:100%; }
.full-height{ min-height:100%; }

resize.js

/**
* Redimensiona a imagem de acordo com o tamanho da janela
* @param {jQueryObject} image
* @param {Integer} imgWidth
* @param {Integer} imgHeight
*/
function resizeBackground(image, imgWidth, imgHeight){
    var win = $(window),
        winWidth = win.width(),
        winHeight = win.height(),
        aspectRatio = winWidth/winHeight;
        imgAspectRatio = imgWidth/imgHeight;
    
    if ( aspectRatio < imgAspectRatio ) {
        image.removeClass('full-width').addClass('full-height');
    } else if ( aspectRatio > imgAspectRatio ) {
        image.removeClass('full-height').addClass('full-width');
    }
}