Craft\ImagerService::_getSaveOptions PHP Method

    private function _getSaveOptions($extension, $transform)
    {
        switch (strtolower($extension)) {
            case 'jpg':
            case 'jpeg':
                return array('jpeg_quality' => $this->getSetting('jpegQuality', $transform));
                break;
            case 'gif':
                return array('flatten' => false);
                break;
            case 'png':
                return array('png_compression_level' => $this->getSetting('pngCompressionLevel', $transform));
                break;
            case 'webp':
                return array('webp_quality' => $this->getSetting('webpQuality', $transform), 'webp_imagick_options' => $this->getSetting('webpImagickOptions', $transform));
                break;
        }
        return array();
    }