前段时间在开发中，遇到需要给背景层加颜色遮罩的项目，现在特定总结一下给背景图层加颜色遮罩的方法。
方法一：通过定位叠加(注意层级)
<div class="wrap1"> <div class="inner"> </div></div>.wrap1 { position: relative; width: 1200px; height: 400px; background: rgba(0, 0, 0, .5);}.wrap1 .inner { position: absolute; left: 0; right: 0; top: 0; bottom: 0; background: url(ban8.jpg) no-repeat center center; background-size: cover; z-index: -1;}方法二：通过伪类元素叠加
<div class="wrap2"></div>.wrap2 { position: relative; width: 1200px; height: 400px; background: url(ban8.jpg) no-repeat center center; background-size: cover;}.wrap2::before { content: ""; position: absolute; left: 0; right: 0; bottom: 0; top: 0; background-color: rgba(0, 0, 0, .5); z-index: 2;}方法三：CSS3颜色叠加background-blend-mode:multiply;(正片叠底)
<div class="wrap3"></div>.wrap3 { position: relative; width: 1200px; height: 400px; background: url(ban8.jpg) rgba(0, 0, 0, .5) no-repeat center center; background-blend-mode: multiply;}拓展：背景模糊加颜色叠加
.wrap4 { position: relative; width: 1200px; height: 400px; background: url(ban8.jpg) rgba(0, 0, 0, .5) no-repeat center center; background-blend-mode: multiply; filter: blur(2px); overflow: hidden;}如有问题欢迎大家讨论指出，如有更好的方法，请不吝赐教，谢谢~~