css最简单的在背景图片上显示模糊背景色的方法

<div class="footu"></div>
<style>
.footu{
background: url() rgba(0,0,0,.4);
background-repeat: no-repeat;
background-position: center center;
background-size: cover;
height:200px;
background-blend-mode: multiply;
}
</style>