-convert -compress none -resize 66x23 - pgm:- |
-perl -nE '
-$_ eq "P2\n" or die "ascii pgm input required\n" if $. == 1;
-next if $. <= 3;
+convert -compress none +distort SRT '0,0 1,.56 0' -thumbnail ${1:-66x23} - pgm:- |
+perl -e '
+<> eq "P2\n" or die "ascii pgm input required\n";
+<>; <>; # ignore depth, dimensions