1. none <div style="background: url(2.jpg) 50% 50%/ auto auto no-repeat ; 1000px; height: 800px; border:1px solid blue;"/> 2. tile 填充 <div style="background: url(3.jpg) ; 1000px; height: 800px; border:1px solid blue;" /> 3. fill <div style="background: url(3.jpg) 0% 0%/ 100% 100% no-repeat ; 1000px; height: 800px; border:1px solid blue;" /> 4.uniform 判断宽高比例，图片宽高比>div宽高比，width 100% 否则 height100% 图片居中（auto 100%换位置） <div style="background: url(3.jpg) 50% 50%/ auto 100% no-repeat ; 1000px; height: 300px; border:1px solid blue;" /> <div style="background: url(3.jpg) 50% 50%/ 100% auto no-repeat ; 1000px; height: 300px; border:1px solid blue;" /> 5.uniformToFill 跟uniform一样，不过（auto 100%换位置） 6.LeftTop <div style="background: url(3.jpg) 0% 0%/ auto auto no-repeat ; 1000px; height: 300px; border:1px solid blue;" />