If you want to access the parameters of a specific template inside the Helper, you could write a small database query, like so:
use Joomla\CMS\Factory;
use Joomla\Registry\Registry;
class TplCassiopeiaHelper
{
private $params = null;
public function __construct()
{
$this->params = $this->getParams();
// You can now access specific parameters, inside the class, for example:
// $this->params->get('colorName')
}
protected function getParams()
{
$db = Factory::getDbo();
$db->setQuery(
$db->getQuery(true)
->select('params')
->from('#__template_styles')
->where('template = ' . $db->q('cassiopeia'))
->where('client_id = 0')
);
$registry = new Registry;
$registry->loadString($db->loadResult());
return $registry;
}
}
Or, when you instantiate the helper class, you could pass $this->params
as a constructor argument.