jQuery : centrer une image en X et Y dans une div

// CENTER ZOOM IMAGE X+Y
        zoom_width = $('#container #main .wrap #zoom img').width();
        zoom_height = $('#container #main .wrap #zoom img').height();
        var zoom_divheight =  $('#container #main .wrap #zoom').height();
        $('#container #main .wrap #zoom img').css('left', '50%');
        $('#container #main .wrap #zoom img').css('right', '50%');
        $('#container #main .wrap #zoom img').css('marginTop', ''+((zoom_divheight-zoom_height)/2)+'px');
        $('#container #main .wrap #zoom img').css('marginLeft', '-'+(zoom_width/2)+'px');

<div id="zoom">
                                <div class="bg-wrap">
                                    <a href="#" rel="temp/produit-zoom-xxl.jpg"><img src="temp/produit-zoom.jpg" alt="zoom" /></a>
                                </div>
                            </div>

/* PRODUCTS * ZOOM */
#container #main .wrap #zoom {
    width:570px;
    height: 600px;
    float:left;
    position: relative;
}
#container #main .wrap #zoom .bg-wrap {
    width: 100%;
    height: 100%;
    background:#FFF;
}
#container #main .wrap #zoom img {
    position: absolute;
    cursor: crosshair;
    border:1px solid red;
}