鼠标滑过 图片上出现蒙版

.ulWrap p{
    width: 1200px;
    height: 0px;
    background: rgba(0,0,0,0.7);
    position: absolute;
    top: 0px;
    z-index: 2;
    color: #fff;
    text-align: center;
    font-size: 18px;
    line-height: 32px;
    transition:height 1.5s ease;
    display: none;
}
.ulWrap>div:hover .w_hide{
    height: 32px;
    display: block;
}