materio-d8/web/modules/custom/images_styles_gen/src/CreateImagesStyles.php

<?php

namespace Drupal\images_styles_gen;


// use Drupal\node\Entity\Node;

class CreateImagesStyles {

  public static function createStyles($item, &$context){
    $context['sandbox']['progress']++;
    $context['sandbox']['current_file'] = $item->uri;
    // $message = 'Creating Styles ...';
    $results = array();

    // foreach ($items as $item) {
      $results[] = $item->style->createDerivative($item->uri, $item->destination);
    // }
    // $styles_storage = \Drupal::entityTypeManager()->getStorage('image_style');
    // $styles = $styles_storage->loadMultiple();
    //
    // foreach ($fids as $fid) {
    //   /** @var \Drupal\file\FileInterface|null $file*/
    //   $file_entity = \Drupal::entityTypeManager()->getStorage('file')->load($fid);
    //   $file_uri = $file_entity->getFileUri();
    //   $image = \Drupal::service('image.factory')->get($file_uri);
    //   // \Drupal::logger('images_styles_gen')->notice("file_uri is $file_uri");
    //
    //   if ($image->isValid()) {
    //     /** @var \Drupal\image\Entity\ImageStyle $style */
    //     foreach ($styles as $style) {
    //       $destination = $style->buildUri($file_uri);
    //       // if destination exists skip
    //       if (file_exists($destination)) continue; // skip existing files
    //
    //       $results[] = $style->createDerivative($file_uri, $destination);
    //       // \Drupal::logger('images_styles_gen')->notice("Generated style $file_uri to $destination");
    //     }
    //
    //   }
    //
    //
    // }
    // $context['message'] = $message;
    // $context['results'] = $results;
    $context['message'] = $item->uri . ' processed.';
    $context['results'][] = $item->destination;
  }

  public static function createStylesFinishedCallback($success, $results, $operations) {
    // The 'success' parameter means no fatal PHP errors were detected. All
    // other error management should be handled using 'results'.
    if ($success) {
      $message = \Drupal::translation()->formatPlural(
        count($results),
        'One image processed.', '@count image processed.'
      );
    }
    else {
      $message = t('Finished with an error.');
    }
    drupal_set_message($message);
  }
}