Imager determines pnm subtype only by number of channels,
so reduce the palette to obtain a P4 format as requested.
my $img = Games::Wormy::Render->composite(
map { $data->{levels}->[$_] } @request
) or die "empty result for levels\n";
+ if ($opt{format} ~~ 'pbm') {
+ $img = $img->to_paletted({make_colors => 'mono'});
+ $opt{format} = 'pnm';
+ }
$img->write(
$opt{output} ? (file => $opt{output}) : (fh => \*STDOUT),
type => $opt{format} // 'pnm',