rollover imagenes

El siguiente código actuaría en todas las imágenes contenidas dentro de un elemento cuya clase sea "item".

<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js" type="text/javascript"></script>
<script type="text/javascript">
    $(window).load(function(){
        $(".item img").fadeIn(500);

        $('.item img').each(function(){
            var el = $(this);
            el.css({"position":"absolute"}).wrap("<div class='img_wrapper' style='display: inline-block'>").clone().addClass('img_grayscale').css({"position":"absolute","z-index":"998","opacity":"1"}).insertBefore(el)

.queue(function(){
                var el = $(this);
                el.parent().css({"width":this.width,"height":this.height});
                el.dequeue();
            });
            this.src = grayscale(this.src);
        });

        $('.item img').mouseover(function(){
            $(this).stop().animate({opacity:0}, 500);
        })
        $('.img_grayscale').mouseout(function(){
            $(this).parent().find('img:first').stop().animate({opacity:1}, 500);

        });
    });

    function grayscale(src){
        var canvas = document.createElement('canvas');
        var ctx = canvas.getContext('2d');
        var imgObj = new Image();
        imgObj.src = src;
        canvas.width = imgObj.width;
        canvas.height = imgObj.height;
        ctx.drawImage(imgObj, 0, 0);
        var imgPixels = ctx.getImageData(0, 0, canvas.width, canvas.height);
        for(var y = 0; y < imgPixels.height; y++){
            for(var x = 0; x < imgPixels.width; x++){
                var i = (y * 4) * imgPixels.width + x * 4;
                var avg = (imgPixels.data[i] + imgPixels.data[i + 1] + imgPixels.data[i + 2]) / 3;
                imgPixels.data[i] = avg;
                imgPixels.data[i + 1] = avg;
                imgPixels.data[i + 2] = avg;
            }
        }
        ctx.putImageData(imgPixels, 0, 0, 0, 0, imgPixels.width, imgPixels.height);
        return canvas.toDataURL();
    }
</script>