Validator::extend('base64image', function ($attribute, $value, $parameters, $validator) {
            $explode = explode(',', $value);
            $allow = ['png', 'jpg', 'svg'];
            $format = str_replace(
                [
                    'data:image/',
                    ';',
                    'base64',
                ],
                [
                    '', '', '',
                ],
                $explode[0]
            );
            // check file format
            if (!in_array($format, $allow)) {
                return false;
            }
            // check base64 format
            if (!preg_match('%^[a-zA-Z0-9/+]*={0,2}$%', $explode[1])) {
                return false;
            }
            return true;
        });