Pl_PNGFilter::finish()
{
    if (this->pos)
    {
	// write partial row
	processRow();
    }
    this->prev_row = 0;
    this->cur_row = buf1;
    this->pos = 0;
    memset(this->cur_row, 0, this->bytes_per_row + 1);

    getNext()->finish();
}
Pl_PNGFilter::finish()
{
    if (this->pos)
    {
	 
	processRow();
    }
    this->prev_row = 0;
    this->cur_row = buf1;
    this->pos = 0;
    memset(this->cur_row, 0, this->bytes_per_row + 1);

    getNext()->finish();
}