Store the values passed to a toolkit call.
$op: One of the image toolkit operations: 'get_info', 'load', 'save', 'settings', 'resize', 'rotate', 'crop', 'desaturate'.
$args: Values passed to hook.
function _image_test_log_call($op, $args) {
$results = state()
->get('image_test.results') ?: array();
$results[$op][] = $args;
state()
->set('image_test.results', $results);
}