#!/usr/bin/perl
mkdir "snap", 0777 unless -d "snap"; 
chdir "snap-orig" 
  or die "where is snap-orig dir?";
@files = <*.png>;
for my $file (@files) {
  print "trimming $file\n";
  system "pngtopnm $file | pnmcrop "
       . "| pnmtopng > ../snap/$file";
}