compass-retina-sprites.scss

@mixin sprite-background($name, $folder) {
  $sprites: sprite-map("#{$folder}/*.png");
  $sprites-retina: sprite-map("#{$folder}@2x/*.png");

  background-image: sprite-url($sprites);
  background-position: sprite-position($sprites, $name);
  background-repeat: no-repeat;
  @include inline-block;
  height: image-height(sprite-file($sprites, $name));
  width: image-width(sprite-file($sprites, $name));
  @media (-webkit-min-device-pixel-ratio: 2), (-o-min-device-pixel-ratio: 3/2), (min-device-pixel-ratio: 2) {
    $ypos: round(nth(sprite-position($sprites-retina, $name), 2) / 2);
    background-position: 0 $ypos;
    background-size: image-width(sprite-file($sprites, $name)) auto;
    background-image: sprite-url($sprites-retina);
  }
}

// Usage.
@import "folder_to_mixin/compass-retina-sprites.scss";
$folder: folder_for_sprites;

.mail-icon {
  @include sprite-background(mail, $folder);
}