大小图片
.brand {
display: inline-block;
width: 30px;
height: 18px;
background-image: url('../../../resource/img/brand@2x.png');
@media (-webkit-min-device-pixel-ratio: 3), (min-device-pixel-ratio: 3) {
background-image: url('../../../resource/img/brand@3x.png');
}
background-size: 30px 18px;
background-repeat: no-repeat;
}
//选择是2x图片还是3x图片
bg-image($url)
background-image: url($url + "@2x.png")
@media (-webkit-min-device-pixel-ratio: 3),(-min-device-pixel-ratio: 3)
background-image: url($url + "@3x.png")
