public function init()
{
parent::init();
$element = new Zend_Form_Element_Checkbox('useExisting');
$element->setRequired(true);
$element->setValue(1);
$element->setLabel('Use existing image:');
$this->useExisting = $element;
$this->addElement('hidden', 'existingFilename', array('required' => true, 'ignore' => false, 'decorators' => array('ViewHelper')));
}