Acme-Steganography-Image-Png

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Png.pm  view on Meta::CPAN

use vars qw($VERSION @ISA);

use Imager;
require Class::Accessor;
use Carp;

@ISA = qw(Class::Accessor);

$VERSION = '0.06';

my @keys = qw(offset data section x y datum_length done filename_generator
	      suffix);

# What arguments can we accept to the constructor.
# Am I reinventing the wheel here?
my %keys;
@keys{@keys} = ();

sub _keys {
  return \%keys;
}

Acme::Steganography::Image::Png->mk_accessors(@keys);

# This will get refactored out at some point to support other formats.
sub generate_header {
    my ($self) = shift;
    my $section = $self->section;

    my $header = pack 'w', $section;
    if (!$section) {
	$header .= pack 'w', length ${$self->data};
    }
    $header;
}

sub default_filename_generator {
  my $state = shift;
  $state ||= 0;
  my $new_state = $state+1;
  # really unimaginative filenames by default
  ($state, $new_state);

Png.pm  view on Meta::CPAN

# Raw data as a greyscale PNG

sub make_image {
  my $self = shift;
  my $img = new Imager;
  $img->read(data=>$_[0], type => 'raw', xsize => $self->x,
	     ysize => $self->y, datachannels=>1, storechannels=>1, bits=>8);
  $img;
}

sub calculate_datum_length {
  my $self = shift;
  $self->x * $self->y;
}

sub extract_payload {
  my ($class, $img) = @_;
  my $datum;
  $img->write(data=> \$datum, type => 'raw');
  $datum;
}

Png.pm  view on Meta::CPAN

@ISA = 'Acme::Steganography::Image::Png::RGB';

# Raw data in the low bits of a colour image

Acme::Steganography::Image::Png->mk_accessors('raw');

sub extract_payload {
  my ($class, $img) = @_;
  my ($raw, $data);
  $img->write(data=> \$raw, type => 'raw');
  my $end = length ($raw)/3;

  for (my $offset = 0; $offset < $end; ++$offset) {
    my ($red, $green, $blue) = unpack 'x' . ($offset * 3) . 'C3', $raw;
    my $datum = (($red & 0x1F) << 11) | (($green & 0x1F) << 6) | ($blue & 0x3F);
    $data .= pack 'n', $datum;
  }
  $data;
}

sub make_image {
  my $self = shift;
  # We get a copy to play with
  my $raw = $self->raw;
  my $offset = length ($raw)/3;
  my $img = new Imager;

  while ($offset--) {
    my $datum = unpack 'x' . ($offset * 2) . 'n', $_[0];
    my $rgb = substr ($raw, $offset * 3, 3);
    # Pack 16 bits into the low bits of R G and B
    $rgb &= "\xE0\xE0\xC0";
    $rgb |= pack 'C3', $datum >> 11, ($datum >> 6) & 0x1F, $datum & 0x3F;
    substr($raw, $offset * 3, 3, $rgb);
  }
  $img->read(data=>$raw, type => 'raw', xsize => $self->x,
	     ysize => $self->y, datachannels => 3,interleave => 0);
  $img;
}

sub calculate_datum_length {
  my $self = shift;
  $self->x * $self->y * 2;
}

package Acme::Steganography::Image::Png::RGB::556FS;

use vars '@ISA';
@ISA = 'Acme::Steganography::Image::Png::RGB::556';

# Raw data in the low bits of a colour image, with Floyd-Steinberg dithering

Png.pm  view on Meta::CPAN

@ISA = 'Acme::Steganography::Image::Png::RGB';

# Raw data in the low bits of a colour image

Acme::Steganography::Image::Png->mk_accessors('raw');

sub extract_payload {
  my ($class, $img) = @_;
  my ($raw, $data);
  $img->write(data=> \$raw, type => 'raw');
  my $end = length ($raw)/3;

  for (my $offset = 0; $offset < $end; ++$offset) {
    my ($red, $green, $blue) = unpack 'x' . ($offset * 3) . 'C3', $raw;
    my $datum = (($red & 0x7) << 5) | (($green & 0x3) << 3) | ($blue & 0x7);
    $data .= chr $datum;
  }
  $data;
}

sub make_image {
  my $self = shift;
  # We get a copy to play with
  my $raw = $self->raw;
  my $offset = length ($raw)/3;
  my $img = new Imager;

  while ($offset--) {
    my $datum = unpack "x$offset C", $_[0];
    my $rgb = substr ($raw, $offset * 3, 3);
    # Pack 8 bits into the low bits of R G and B
    $rgb &= "\xF8\xFC\xF8";
    $rgb |= ("\x07\x03\x07" & pack 'C3', $datum >> 5, $datum >> 3, $datum);
    substr($raw, $offset * 3, 3, $rgb);
  }
  $img->read(data=>$raw, type => 'raw', xsize => $self->x,
	     ysize => $self->y, datachannels => 3,interleave => 0);
  $img;
}

sub calculate_datum_length {
  my $self = shift;
  $self->x * $self->y;
}

package Acme::Steganography::Image::Png::RGB;

use vars '@ISA';
@ISA = 'Acme::Steganography::Image::Png';

# Raw data in the low bits of a colour image

Png.pm  view on Meta::CPAN

  $self->raw($raw);

  $self->SUPER::write_images;
}
package Acme::Steganography::Image::Png;

sub generate_next_image {
    my ($self) = shift;
    my $datum = $self->generate_header;
    my $offset = $self->offset;
    my $datum_length = $self->datum_length;
    # Fill our blob of data to the correct length
    my $grab = $datum_length - length $datum;
    $datum .= substr ${$self->data()}, $offset, $grab;
    $self->offset($offset + $grab);

    if (length $datum < $datum_length) {
      # Need to pad it. NUL is so uninspiring.
      $datum .= "N" x ($datum_length - length $datum);
      $self->done(1);
    } elsif (length ${$self->data()} == $self->offset) {
      warn length $datum;
    }
    $self->section($self->section + 1);

    $self->make_image($datum);
}

sub new {
  my $class = shift;
  croak "Use a classname, not a reference for " . __PACKAGE__ . "::new"
    if ref $class;

Png.pm  view on Meta::CPAN

}

sub type {
  'png';
}

sub write_images {
  my $self = shift;
  $self->section(0);
  $self->offset(0);
  $self->datum_length($self->calculate_datum_length());
  my $type = $self->type;
  my $filename_generator
    = $self->filename_generator || \&default_filename_generator;

  my @filenames;

  my ($filename, $state);
  while (!$self->done()) {
    my $image = $self->generate_next_image;
    ($filename, $state) = &$filename_generator($state);

Png.pm  view on Meta::CPAN

    push @filenames, $filename;
  }
  @filenames;
}

# package method
sub read_files {
  my $class = shift;
  # This is intentionally a "sparse" array to avoid some "interesting" DOS
  # possibilities.
  my $length;
  my %got;
  foreach my $file (@_) {
    my $img = new Imager;
    $img->open(file => $file) or carp "Can't read '$file': " . $img->errstr;
    my $payload = $class->extract_payload($img);
    my $datum;
    my $section;
    ($section, $datum) = unpack "wa*", $payload;
    if ($section == 0) {
      # Oops. Strip off the length.
      ($length, $datum) = unpack "wa*", $datum;
    }
    $got{$section} = $datum;
  }
  carp "Did not find first section in files @_" unless defined $length;

  my $data = join '', map {$got{$_}} sort {$a <=> $b} keys %got;
  substr ($data, $length) = '';

  $data;
}

1;
__END__

=head1 NAME

Acme::Steganography::Image::Png - hide data (badly) in Png images

t/Tester.pm  view on Meta::CPAN

my $data;

{
  local $/;
  open FH, $^X or die "Can't open $^X: $!";
  binmode FH;
  $data = <FH>;
}

is (length $data, -s $^X, "Read in $^X for testing");

sub test_package {
    my $package = shift;

    my $writer = $package->new();

    ok($writer, "Testing $package");

    $writer->data(\$data);

    my @filenames = $writer->write_images(@_);

    cmp_ok (@filenames, '>', 0, "Generated some images");

    foreach (@filenames) {
	ok (-e $_, "$_ exists");
    }

    my $reread = $package->read_files(reverse @filenames);

    is (length $reread, length $data, "Same length");
    # No. I don't want not equal diagnsotics sent to stderr
    ok ( $reread eq $data, "Same contents");

    unlink @filenames unless $::DEBUG;
}

1;