You can also get full image path of product using this code :
protected $_product;
protected $_storeManager;
public function __construct(
...
\Magento\Catalog\Model\Product $product,
\Magento\Store\Model\StoreManagerInterface $storeManager,
...
)
{
...
$this->_product = $product;
$this->$_storeManager = $storeManager;
...
}
public function execute(){
$product = $this->_product->load('product_id');
$mediaPath = $this->_storeManager->getStore()->getBaseUrl(\Magento\Framework\UrlInterface::URL_TYPE_MEDIA);
$product_image_full_path = $mediaPath . 'catalog/product' . $product->getImage();
}
Hope, it will useful for you !!