@media print and (min-resolution: 300dpi) {}
@media print and (min-resolution: 300dpcm) {}
@media print and (min-resolution: 300dppx) {}
@media print and (min-resolution: 300x) {}

.box {
    background-image: -webkit-image-set(
            url("small-balloons.jpg") 1x,
            url("large-balloons.jpg") 2x);
    background-image: image-set(
            url("small-balloons.jpg") 1x,
            url("large-balloons.jpg") 2x);
}