trait ImageStyleGenerationTrait in Flysystem 2.0.x

trait ImageStyleGenerationTrait {

  /**
   * Generates an image style for a file target.
   *
   * @param string $target
   *   The file target.
   *
   * @return bool
   *   True on success, false on failure.
   */
  protected function generateImageStyle($target) {
    if (strpos($target, 'styles/') !== 0 || substr_count($target, '/') < 3) {
      return FALSE;
    }
    list(, $style, $scheme, $file) = explode('/', $target, 4);
    if (!($image_style = ImageStyle::load($style))) {
      return FALSE;
    }
    $image_uri = $scheme . '://' . $file;
    $derivative_uri = $image_style
      ->buildUri($image_uri);
    if (!file_exists($image_uri)) {
      $path_info = pathinfo($image_uri);
      $converted_image_uri = $path_info['dirname'] . '/' . $path_info['filename'];
      if (!file_exists($converted_image_uri)) {
        return FALSE;
      }
      else {

        // The converted file does exist, use it as the source.
        $image_uri = $converted_image_uri;
      }
    }
    $lock_name = 'image_style_deliver:' . $image_style
      ->id() . ':' . Crypt::hashBase64($image_uri);
    if (!file_exists($derivative_uri)) {
      $lock_acquired = \Drupal::lock()
        ->acquire($lock_name);
      if (!$lock_acquired) {
        return FALSE;
      }
    }
    $success = file_exists($derivative_uri) || $image_style
      ->createDerivative($image_uri, $derivative_uri);
    if (!empty($lock_acquired)) {
      \Drupal::lock()
        ->release($lock_name);
    }
    return $success;
  }

}