/**
 * Implements hook_image_effect_info_alter().
 */
function {{ machine_name }}_image_effect_info_alter(&$effects) {
  // Override the Image module's crop effect with more options.
  $effects['image_crop']['effect callback'] = 'mymodule_crop_effect';
  $effects['image_crop']['dimensions callback'] = 'mymodule_crop_dimensions';
  $effects['image_crop']['form callback'] = 'mymodule_crop_form';
}