点击图片放大至原始图片大小

var _w = parseInt($(window).width());//获取浏览器的宽度
    $("#abc img").each(function(i){
        var img = this;
        var realWidth;//真实的宽度
        var realHeight;//真实的高度
        $("<img/>").attr("src", $(img).attr("src")).load(function() {
            realWidth = this.width;
            realHeight = this.height;

        })
        var flag = 1;
        $(img).on("click",function () {
            if (flag == 1) {
                if(realWidth>=_w){
                    $(img).css({
                        "width": "100%",
                        "height": "auto",
                        "position": "fixed",
                        "top": "50%",
                        "left": "50%",
                        "margin-top": "-30%",
                        "margin-left": "-50%"
                    });
                }else{
                    $(img).css({
                        "width": realWidth,
                        "height": realHeight,
                        "position": "fixed",
                        "top": "50%",
                        "left": "50%",
                        "margin-top": -realHeight / 2,
                        "margin-left": -realWidth / 2
                    });
                }
                flag = 0;
            } else {
                $(img).css({
                    "width": 500,
                    "height": 400,
                });
                flag = 1;
            }
        });
    });