public function merge($percentage)
    {
        $this->setProperties($percentage);

        imagecopyresampled(
            $this->sourceImage->getImageResource(),
            $this->mergeImage->getImageResource(),
            $this->centerX,
            $this->centerY,
            0,
            0,
            $this->postMergeImageWidth,
            $this->postMergeImageHeight,
            $this->mergeImageWidth,
            $this->mergeImageHeight
        );

        return $this->createImage();
    }