Model/Product/Image.php
private function fastlyResize()
    {
        if ($this->getWidth() === null && $this->getHeight() === null) {
            return $this;
        }

        $this->adjustSize();

        return $this;
    }
private function fastlyResize()
    {
        if ($this->getWidth() === null && $this->getHeight() === null) {
            return $this;
        }

        $this->adjustSize();

        return $this;
    }
Fastly implementation of resize

@see \Magento\Framework\Image\Adapter\AbstractAdapter
@return \Magento\Catalog\Model\Product\Image