Retina Image Mixin

retinaImages.sass

@mixin image-2x($image, $width, $height) {
  @media (min--moz-device-pixel-ratio: 1.3),
         (-o-min-device-pixel-ratio: 2.6/2),
         (-webkit-min-device-pixel-ratio: 1.3),
         (min-device-pixel-ratio: 1.3),
         (min-resolution: 1.3dppx) {
    background-image: url($image);
    background-size: $width + px $height + px;
    background-size: $width / 10 + rem $height / 10 + rem;
  }
}
// Usage
.logo{
    background:url(logo.png) no-repeat;
    @include image-2x(logo-hd.png", 120, 30);
}