typename T1::accumulator_type tot(*iter*(length+1));
for (x=0;x<length && iter!=end;x++,++iter) tot+=*iter;
iter=pen.x();
for (x=0;x<w && iter!=end;x++,++iter,outpen.inc_x())
typename T1::accumulator_type tot(*iter*(length+1));
for (x=0;x<length && iter!=end;x++,++iter) tot+=*iter;
iter=pen.x();
for (x=0;x<w && iter!=end;x++,++iter,outpen.inc_x())