public function setScale($scale)
    {
        $valid = ['b', 'c', 'f', 'r'];
        $scale = substr((string) $scale, 0, 1);
        $scale = in_array($scale, $valid)
            ? $scale
            : (!empty($this->thumbConf['cropping']) ? substr($this->thumbConf['cropping'], 0, 1) : 'c');

        $this->scale = $scale;

        return $this;
    }