/**
* Render the chart image
*
* @access public
* @param string name of the file to render the image to (optional)
*/
function render($imgType, $fileName = null)
{
$this->computeBound();
$this->computeLabelMargin();
$this->createImage();
$this->printLogo();
$this->printTitle();
$this->printAxis();
$this->printLine();
parent::render($imgType, $filename);
}