html:
     
      
       css:(1)这种情况下图片可以填充整个div，但背景色和原背景图片不一致background: url(../images/mall-bg.png) no-repeat center center fixed;height: 11.5rem;width: 100%;-webkit-background-size: cover;-moz-background-size: cover;-o-background-size: cover;background-size: cover;display: flex;justify-content: space-around;align-items: center;（2）和背景图片基本一致，但背景图片在宽度上没有填充整个div，左右两边有间距background: url(../images/mall-bg.png);background-size: 100%;height: 9rem;（3）背景图片在宽度上填充整个div，且基本与原背景图片效果一致width: 100%;display: flex;justify-content: space-around;align-items: center;background: url(../images/mall-bg.png);height: 9rem;background-position: center;background-size: 110% 100%;