damonsk

.background-image-retina(@file, @type, @width, @height) {
    background-image: url("@{file}.@{type}");

    @media (-webkit-min-device-pixel-ratio: 2), (-moz-min-device-pixel-ratio: 2) {
        & {
            background-image: url("@{file}@2x.@{type}");
            -webkit-background-size: @width @height;
        }
    }
}