Drupal 8 *.theme file snippets for Twig template

Drupal8-theme-snippets.php

<?php
    
use Drupal\image\Entity\ImageStyle;
use \Drupal\file\Entity\File;

function theme_preprocess_page(&$vars) {

  if (($node = \Drupal::routeMatch()->getParameter('node')) && $node instanceof \Drupal\node\NodeInterface) {
    
    // Get imagestyle url for use in Twig template
    if(isset($node->field_header_image->target_id)) {
      $path = File::load($node->field_header_image->target_id)->getFileUri();
      $url = ImageStyle::load('header-style')->buildUrl($path);
    } else {
      $url = '';
    }
    $vars['header_background_image_url'] = $url;

    // Get rendered field without label for use in Twig template
    if (isset($node->field_header_cta_button)) {
      $field_header_cta_button = $node->get('field_header_cta_button');
      $vars['header_cta_button'] = $field_header_cta_button->view(array('label' => 'hidden'));
    }

  }
}