Pl_PNGFilter::processRow()
{
    if (this->action == a_encode)
    {
	encodeRow();
    }
    else
    {
	decodeRow();
    }
}
Pl_PNGFilter::processRow()
{
    if (this->action == a_encode)
    {
	encodeRow();
    }
    else
    {
	decodeRow();
    }
}