public function cmdClearImageStyle()
    {
        $id = $this->getParam(0);
        $all = $this->getParam('all');

        if (!isset($id) && empty($all)) {
            $this->errorAndExit($this->text('Invalid command'));
        }

        $result = false;

        if (isset($id)) {

            if (!is_numeric($id)) {
                $this->errorAndExit($this->text('Invalid argument'));
            }

            $result = $this->image_style->clearCache($id);
        } else if (!empty($all)) {
            $result = $this->image_style->clearCache();
        }

        if (empty($result)) {
            $this->errorAndExit($this->text('Unexpected result'));
        }

        $this->output();
    }