以鼠标位置为中心的图片滚动放大缩小

 //以鼠标位置为中心的图片滚动放大缩小
$(document).on("mousewheel","#mask img",function(ev){
    var oImg = this;
    var ev = event || window.event;//返回WheelEvent
    ev.preventDefault();
    var delta = ev.detail ? ev.detail > 0 : ev.wheelDelta < 0;
    var ratioL = (ev.clientX - oImg.offsetLeft) / oImg.offsetWidth,
        ratioT = (ev.clientY - oImg.offsetTop) / oImg.offsetHeight,
        ratioDelta = !delta ? 1 + 0.1 : 1 - 0.1,
        w = parseInt(oImg.offsetWidth * ratioDelta),
        h = parseInt(oImg.offsetHeight * ratioDelta),
        l = Math.round(ev.clientX - (w * ratioL)),
        t = Math.round(ev.clientY - (h * ratioT));
        with(oImg.style) {
            width = w +'px';
            height = h +'px';
            left = l +'px';
            top = t +'px';
        }
});

废话不多说，相信程序员看了都知道怎么用。