/**
* returns an IE hex string for a color with an alpha channel
* suitable for passing to IE filters.
*/
public static function ie_hex_str($color)
{
if (!$color instanceof SassColour) {
$color = new SassColour($color);
}
$alpha = str_replace(',', '.', round($color->alpha * 255));
$alpha_str = str_pad(dechex($alpha), 2, '0', STR_PAD_LEFT);
$col = $color->asHex(FALSE);
return new SassString(strtoupper('#' . $alpha_str . $col));
}