只需要为添加效果的图片定义一个伪类

img.zoom-img:hover {
          -webkit-transform: scale(1.15);    -webkit-transition-timing-function: ease-out;    -webkit-transition-duration: 20000ms;    -moz-transform: scale(1.15);    -moz-transition-timing-function: ease-out;    -moz-transition-duration: 750ms;    overflow: hidden;}