_sass/vendor/bourbon/css3/_image-rendering.scss

@mixin image-rendering ($mode:auto) {

  @if ($mode == crisp-edges) {
      -ms-interpolation-mode: nearest-neighbor; // IE8+
      image-rendering: -moz-crisp-edges;
      image-rendering: -o-crisp-edges;
      image-rendering: -webkit-optimize-contrast;
      image-rendering: crisp-edges;
  }

  @else {
      image-rendering: $mode;
  }
}