Magento 2 template processor programmatically

The post will guide how to use a template processor to filter variables, widgets in tag {{…}} to HTML.

Use filter display content of a block

<?php

require dirname(__FILE__) . '/app/bootstrap.php';
$bootstrap = \Magento\Framework\App\Bootstrap::create(BP, $_SERVER);

class Outslide extends \Magento\Framework\App\Http
    implements \Magento\Framework\AppInterface {
    public function launch()
    {

        $this->_state->setAreaCode('frontend'); 
        // $this->_state->setAreaCode('adminhtml'); 
        // $this->_state->setAreaCode(\Magento\Framework\App\Area::AREA_FRONTEND);
        // $this->_state->setAreaCode(\Magento\Framework\App\Area::AREA_ADMINHTML);

        $block = $this->_objectManager->create('\Magento\Cms\Model\Block');   
        $filterProvider = $this->_objectManager->create('Magento\Cms\Model\Template\FilterProvider');
        $storeManager = $this->_objectManager->create('Magento\Store\Model\StoreManagerInterface');

        $blockId = 1; // Id of block you want get content
        $storeId = $storeManager->getStore()->getId();
        $block->setStoreId($storeId)->load($blockId);    
        $content = $block->getContent();
        $html = $filterProvider->getBlockFilter()->setStoreId($storeId)->filter($content);
        echo $html;
        //the method must end with this line
        return $this->_response;
    }
}

/** @var \Magento\Framework\App\Http $app */
$app = $bootstrap->createApplication('Outslide');
$bootstrap->run($app);

Use filter display content of a page

<?php

require dirname(__FILE__) . '/app/bootstrap.php';
$bootstrap = \Magento\Framework\App\Bootstrap::create(BP, $_SERVER);

class Outslide extends \Magento\Framework\App\Http
    implements \Magento\Framework\AppInterface {
    public function launch()
    {

        $this->_state->setAreaCode('frontend'); 
        // $this->_state->setAreaCode('adminhtml'); 
        // $this->_state->setAreaCode(\Magento\Framework\App\Area::AREA_FRONTEND);
        // $this->_state->setAreaCode(\Magento\Framework\App\Area::AREA_ADMINHTML);

        $page = $this->_objectManager->create('\Magento\Cms\Model\Page');   
        $filterProvider = $this->_objectManager->create('Magento\Cms\Model\Template\FilterProvider');
        $storeManager = $this->_objectManager->create('Magento\Store\Model\StoreManagerInterface');

        $pageId = 1; // Id of Page you want get content
        $storeId = $storeManager->getStore()->getId();
        $page->setStoreId($storeId)->load($pageId);    
        $content = $page->getContent();
        $html = $filterProvider->getBlockFilter()->setStoreId($storeId)->filter($content);
        echo $html;
        //the method must end with this line
        return $this->_response;
    }
}

/** @var \Magento\Framework\App\Http $app */
$app = $bootstrap->createApplication('Outslide');
$bootstrap->run($app);

Use filter display description product with a programmatically

<?php

require dirname(__FILE__) . '/app/bootstrap.php';
$bootstrap = \Magento\Framework\App\Bootstrap::create(BP, $_SERVER);

class Outslide extends \Magento\Framework\App\Http
    implements \Magento\Framework\AppInterface {
    public function launch()
    {

        $this->_state->setAreaCode('frontend'); 
        // $this->_state->setAreaCode('adminhtml'); 
        // $this->_state->setAreaCode(\Magento\Framework\App\Area::AREA_FRONTEND);
        // $this->_state->setAreaCode(\Magento\Framework\App\Area::AREA_ADMINHTML);

        $productRepository = $this->_objectManager->create('Magento\Catalog\Model\ProductRepository');
        $filterProvider = $this->_objectManager->create('Magento\Cms\Model\Template\FilterProvider');
        $storeManager = $this->_objectManager->create('Magento\Store\Model\StoreManagerInterface');
        // YOU WANT TO LOAD BY ID?
        $id = 1;
        // YOU WANT TO LOAD BY SKU?
        $sku = "YOUR SKU HERE";

        if($id) {
            $product = $productRepository->getById($id);
        }
        if($sku) {
            $product = $productRepository->get($sku);
        }

        $descriptionAttributeCode      = "description";
        $storeId = $storeManager->getStore()->getId();
        $description = $product->setStoreId($storeId)->getData($descriptionAttributeCode);
        // echo $description;
        $html = $filterProvider->getBlockFilter()->setStoreId($storeId)->filter($description);
        echo $html;
        echo 'Done!';
        //the method must end with this line
        return $this->_response;
    }
}

/** @var \Magento\Framework\App\Http $app */
$app = $bootstrap->createApplication('Outslide');
$bootstrap->run($app);