How to add classes to views rows programmatically in drupal 7

add_classes_to_views_rows.php

/**
 * Implements hook_views_view_unformatted().
 */
function YOUR_THEME_preprocess_views_view_unformatted(&$vars) {
  $results = $vars['view']->result;

  $iteration = 0;
  foreach ($results as $key => $result) {
    if (empty($result->field_image)) {
      $vars['classes_array'][$key] .= ' empty__' . ($iteration % 5 + 1);
      $iteration++;
    }
  }
}