laravel Gregwar/Captcha图片resource(395) of type (gd)

/**
     * 图片验证码
     */
    public function captcha()
    {
        $phrase = new PhraseBuilder;
        // 设置验证码位数
        $code = $phrase->build(4);
        // 生成验证码图片的Builder对象,配置相应属性
        $builder = new CaptchaBuilder($code, $phrase);
        // 设置背景颜色
        $builder->setBackgroundColor(220, 210, 230);
        $builder->setMaxAngle(25);
        $builder->setMaxBehindLines(10);
        $builder->setMaxFrontLines(10);
        // 可以设置图片宽高及字体
        $builder->build($width = 100, $height = 40, $font = null);
        // 获取验证码的内容
        $phrase = $builder->getPhrase();
        // 生成图片
        header('Cache-Control: no-cache, must-revalidate');
        header('Content-Type:image/jpeg');
        $builder->output();exit;
    }

返回乱码