WooCommerce - Add gallery image to products in a category

<?php
  // add a gallery image to all products in a specific category
  // code goes in functions.php for your child theme
  // in this example, 12 is the category id and 2931 is the media library image id.
  add_filter('woocommerce_product_gallery_attachment_ids', 'add_gallery_image', 10, 2);
  function add_gallery_image($ids, $product) {
    $terms = get_the_terms( $product->post->ID, 'product_cat' );
    foreach ($terms as $term) {
      if ($term->term_id == 12) {
        $ids[] = '2931';
        break;
      }
    }
    return $ids;
  }