Generated by SassMeister.com.

SassMeister-input.scss

// ----
// Sass (v3.3.0.rc.1)
// Compass (v0.13.alpha.10)
// ----

// http://37signals.com/svn/posts/3271-easy-retina-ready-images-using-scss
// Pruebo pasarle background-position

@mixin image-2x($image, $width, $height, $pos-right: 0, $pos-left: 0) {
  @media (min--moz-device-pixel-ratio: 1.3),
         (-o-min-device-pixel-ratio: 2.6/2),
         (-webkit-min-device-pixel-ratio: 1.3),
         (min-device-pixel-ratio: 1.3),
         (min-resolution: 1.3dppx) {
    /* on retina, use image that's scaled by 2 */
    background-image: url($image);
    background-size: $width $height;
    background-position: $pos-right $pos-left;
  }
}

div {
  background: red;
  @include image-2x('test@2x.png', 290px, 290px, 10px, 12px);
}

SassMeister-output.css

div {
  background: red;
}
@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) {
  div {
    /* on retina, use image that's scaled by 2 */
    background-image: url("test@2x.png");
    background-size: 290px 290px;
    background-position: 10px 12px;
  }
}