$(document).ready(function(){

/* background resizable */   
function redimensionnement(){

    var image_width = $('img').width();
    var image_height = $('img').height();
    
    var over = image_width / image_height;
    var under = image_height / image_width;
    
	var body_width = $(window).width();
    var body_height = $(window).height();
	
	
    if (body_width / body_height >= over) {
      $('img').css({
        'width': body_width + 'px',
        'height': Math.ceil(under * body_width) + 'px',
        'left': '0px',
        'top': Math.abs((under * body_width) - body_height) / -2 + 'px'
      });
    } 
	
	else {
      $('img').css({
        'width': Math.ceil(over * body_height) + 'px',
        'height': body_height + 'px',
        'top': '0px',
        'left': Math.abs((over * body_height) - body_width) / -2 + 'px'
      });
    }
}
		
	redimensionnement(); //onload
	
	$(window).resize(function(){
		redimensionnement();
	});

});