webp图像显示黑色背景而不是透明度

Question

When upload png image and convert into webp image using rossell-dk plugin. means it display black background instead of transparent background.

$success = WebPConvert\WebPConvert::convert($pathToImages, $pathToWebpImages, [
            // It is not required that you set any options - all have sensible defaults.
            // We set some, for the sake of the example.
            'quality' => 'auto',
            'max-quality' => 90,
            'converters' =>  [ 'gd', 'imagick', 'wpc', 'ewww']/*,
            'skip-pngs'=>"0"*/
            //'converters' => ['cwebp','webp', 'gd', 'imagick', 'wpc', 'ewww'],  
            // Specify conversion methods to use, and their order
        ]);