$(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(); 
    }); 
 
}); // JavaScript Document