Pop\Image\Gd::setQuality PHP Метод

    public function setQuality($q = null)
    {
        switch ($this->mime) {
            case 'image/png':
                $this->quality = $q < 10 ? 9 : 10 - round($q / 10, PHP_ROUND_HALF_DOWN);
                break;
            case 'image/jpeg':
                $this->quality = round($q);
                break;
            default:
                $this->quality = null;
        }
        return $this;
    }

 public function testPng()
 {
     $i = new Gd(__DIR__ . '/../tmp/test.png');
     $i->setQuality(75)->setOpacity(50)->resizeToWidth(240);
     $this->assertEquals(240, $i->getWidth());
 }