protected function getRequestedUrls()
    {
        $oInput = Factory::service('Input');
        $sUrls  = $oInput->get('urls') ?: $oInput->header('X-Cdn-Urls');
        $aUrls  = !is_array($sUrls) ? explode(',', $sUrls) : $sUrls;
        $aUrls  = array_map('strtolower', $aUrls);

        //  Filter out any which don't follow the format {digit}x{digit}-{scale|crop} || raw
        foreach ($aUrls as &$sDimension) {

            if (!is_string($sDimension)) {
                $sDimension = null;
                continue;
            }

            preg_match_all('/^(\d+?)x(\d+?)-(scale|crop)$/i', $sDimension, $aMatches);

            if (empty($aMatches[0])) {
                $sDimension = null;
            } else {
                $sDimension = [
                    'width'  => !empty($aMatches[1][0]) ? $aMatches[1][0] : null,
                    'height' => !empty($aMatches[2][0]) ? $aMatches[2][0] : null,
                    'type'   => !empty($aMatches[3][0]) ? $aMatches[3][0] : 'crop',
                ];
            }
        }

        return array_filter($aUrls);
    }