nstdio / SVGMagick

        return $val;

    }

    public static function linear(ContainerInterface $container, $slope, $intercept, $filterId = null)

    {

        $config = ['id' => $filterId, 'type' => __FUNCTION__];

        self::buildConfig($config, [

            'slope'     => $slope,

            'intercept' => $intercept,

        ]);

        return self::createAndAppend($container, $config);

    }

    private static function buildConfig(array &$config, array $attributes)

    {

        return self::createAndAppend($container, $config);

    }

    public static function brightness(ContainerInterface $container, $amount, $filterId = null)

    {

        $config = ['id' => $filterId, 'type' => 'linear'];

        self::buildConfig($config, [

            'slope' => $amount,

        ]);

        return self::createAndAppend($container, $config);

    }

    public static function contrast(ContainerInterface $container, $amount, $filterId = null)

    {