$.fn.resizenow = function() {
  //Define image ratio
  var ratio = 480 / 640;//this.height()/this.width();
  
  //Gather browser and current image size
  var imagewidth = $(this).width();
  var imageheight = $(this).height();
  var browserwidth = $(window).width();
  var browserheight = $(window).height();
  var offset;

  //Resize image to proper ratio
  if ((browserheight/browserwidth) > ratio){
    $(this).height(browserheight);
    $(this).width(browserheight / ratio);
    $(this).children().height(browserheight);
    $(this).children().width(browserheight / ratio);
  } else {
    $(this).width(browserwidth);
    $(this).height(browserwidth * ratio);
    $(this).children().width(browserwidth);
    $(this).children().height(browserwidth * ratio);
  }
  $(this).css('left', (browserwidth - $(this).width())/2);
	$(this).css('top', (browserheight - $(this).height())/2);
}