Sass drop shadow mixin for PNG images with transparent backgrounds

gistfile1.sass

@mixin dropShadow($offX: 2, $offY: 2, $blur: 2, $rgba: rgba(0, 0, 0, 0.3), $hex: #B2B2B2) {
  -webkit-filter: drop-shadow(#{$offX}px #{$offY}px #{$blur}px $rgba);
  filter        : url("data:image/svg+xml;utf8,<svg height='0' xmlns='http://www.w3.org/2000/svg'><filter id='drop-shadow'><feGaussianBlur in='SourceAlpha' stdDeviation='" + $blur +"'/><feOffset dx='" + $offX + "' dy='" + $offY + "' result='offsetblur'/><feFlood flood-color='#{$rgba}'/><feComposite in2='offsetblur' operator='in'/><feMerge><feMergeNode/><feMergeNode in='SourceGraphic'/></feMerge></filter></svg>#drop-shadow");
  -ms-filter    : "progid:DXImageTransform.Microsoft.Dropshadow(OffX=" + $offX + ", OffY=" + $offY + ", Color='" + $hex + "')";
  filter        : "progid:DXImageTransform.Microsoft.Dropshadow(OffX=" + $offX + ", OffY=" + $offY + ", Color='" + $hex + "')";
}