获取图片宽、高

var image = new Image();
            var that = this;
            image.onload = function(){
                if ("naturalWidth" in image) { // 现代浏览器
                    that.width = image.naturalWidth;
                    that.height = image.naturalHeight;
                } else { // IE6/7/8
                    that.width = image.width;
                    that.height = image.height;
                }
                image = undefined;
                delete image;
            }