function grayscale($mixedImage, $sDstImage = '')
{
if (is_array($mixedImage)) {
$aRet = array();
foreach ($mixedImage as $s) {
$aRet[] = $this->_grayscale($s, $s);
}
return $aRet;
} else {
return $this->_grayscale($mixedImage, $sDstImage);
}
}