function MY_MODULE_form_process_user_picture(&$form, FormStateInterface &$form_state) {
  $file_name = "";
  $username = "";
  $fid_0 = NULL;
  $user_picture = $form['user_picture'];
  $uid = $form_state->getValue('uid');
  if ($form_state->hasFileElement() && $form_state->hasValue('user_picture')) {
    $username = $form_state->getValue('field_name')[0]['value'];
    $fid_0 = isset($form_state->getValue('user_picture')[0]['fids'][0]) ? $form_state->getValue('user_picture')[0]['fids'][0] : $fid_0;
    /*
      $changed = $form_state->get('user_picture')->getValue() == $form_state->getValue('user_picture');
      //This is not working as $form_state->get() returns null.
    */
    /*
      $changed = $form_state->get('user_picture')->getValue() == $form['user_picture']['#default_value'];
      //This is not working as $form['user_picture']['#default_value'] is null.
    */
      if($changed) {
        // Proceed to rename the file.
      }
    }