Craft\ImagerService::runOptipng PHP Method

    public function runOptipng($file)
    {
        $cmd = $this->getSetting('optipngPath');
        $cmd .= ' ';
        $cmd .= $this->getSetting('optipngOptionString');
        $cmd .= ' ';
        $cmd .= $file;
        $this->executeOptimize($cmd, $file);
    }