qzone.qq.com 背景图的渐入是如何实现的

[bilok]

搜过几次给出的也只是 logo 的渐入渐出效果

[jessynt]

.lay_background .lay_background_img {
opacity: 0;
-webkit-transition: opacity .8s ease;
-moz-transition: opacity .8s ease;
transition: opacity .8s ease
}

.lay_background .lay_background_img_fade_out {
opacity: 1
}