Saas retina background image mixin

gistfile1.sass

@mixin retina-background($image, $type, $width, $height, $position:0 0, $repeat:no-repeat) {
    background-image: url("#{$image}.#{$type}");
    background-position: $position;
    background-repeat: $repeat;

    @media (min--moz-device-pixel-ratio: 1.3),
            (-o-min-device-pixel-ratio: 2.6/2),
            (-webkit-min-device-pixel-ratio: 1.3),
            (min-device-pixel-ratio: 1.3),
            (min-resolution: 1.3dppx) {
        background-image: url("#{$image}@2x.#{$type}");
        background-size: $width $height;
    }
}