@2x@3x图片使用

@media  (-webkit-min-device-pixel-ratio: 2),(min-device-pixel-ratio: 2){
  .imgTest{
    background: url(../images/2x.png) no-repeat; 
  } 
} 
 @media  (-webkit-min-device-pixel-ratio: 3),(min-device-pixel-ratio: 3){
  .imgTest{
    background: url(../images/3x.png) no-repeat; 
  } 
}