#home{
 
background-image:url("https://pic3.zhimg.com/100/v2-71222f24db33136f7daaed04b2a28cec_r.jpeg?source=1940ef5c");}
 
#matrix{position: fixed; top:0; left: 0; z-index: -1; opacity:0.8;}
<!-- 背景动画 -->
<canvas id="c_n9" width="1920" height="990" style="position: fixed; top: 0px; left: 0px; z-index: -1; opacity: 0.5;"></canvas>
<script src="https://files.cnblogs.com/files/jingmoxukong/canvas-nest.min.js"></script>