Remove IDAT chunk of length 0 for png

pngfix.pl

#!/usr/bin/perl -s
# photohop 等で作成するpng には
# 長さ０のIDAT チャンクが作成される事がある
# ImageMagick等でエラーとなり読み込めない事があるので取り除く
#
$src = shift || usage();
$dst = shift || usage();

sub usage {
  print "Remove IDAT chunk of size 0\n";
  print "$0 src-pngfile dst-pngfile\n";
  exit 0;
}

open(FP, '<', $src) || die "Can't open [$src] to read";
if(read(FP, $id, 8) != 8){
  die "Can't read identifier...";
};

if(! $id =~ /PNG/){
  die "not png???\n";
}

open(OUT,  '>', $dst) || die;
print OUT $id;

while(1){
  (read(FP, $_, 8) == 8) || last;
  ($len, $name) = unpack("N a4", $_);
  print "[$len] [$name]\n" if($debug);

  read(FP, $data, $len);
  read(FP, $crc, 4);

  next if(($len == 0)&& $name =~ /IDAT/);

  print OUT $_;
  print OUT $data;
  print OUT $crc;
}
print OUT $_;

close(FP);
close(OUT);

print "Done\n";