File: findimagedupes

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findimagedupes 2.18-7
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#!/usr/bin/perl -w
# $Id: findimagedupes,v 2.18 2008/12/19 01:04:36 jhnc Exp jhnc $
#
# findimagedupes - Finds visually similar or duplicate images
#
# Copyright 2006-2008 by Jonathan H N Chin <code@jhnc.org>.
#
# This program is free software; you may redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
#

use strict;

require 5.006_001;

use Cwd qw(realpath);
use DB_File;
use Digest::MD5 qw(md5_hex);
use Getopt::Long qw(:config no_ignore_case require_order);
use File::MimeInfo::Magic;
use File::Temp qw(tempdir tempfile);
use Graphics::Magick;
use MIME::Base64;
use Pod::Usage;

use lib "/usr/lib/findimagedupes/lib";
use findimagedupes::C;

# ----------------------------------------------------------------------
#
# option parsing
#

use vars qw(
	$null
	$add
	$collection
	@debug %debug
	@fpdb
	$merge
	$nocompare
	$program
	$quiet
	$rescan
	$recurse
	$script
	@scriptCode
	$scriptFile
	$threshold
	@verbosity
	$prune
);

$add = 0;
$quiet = 0;
$threshold = '90%';

my %opt;
GetOptions(
	'0|null'                 => \$null,
	'a|add'                  => \$add,
	'c|collection=s'         => sub { ($collection = $_[1]) =~ s/([.]gqv)?$/.gqv/ },
	'd|debug=s'              => \@debug,
	'f|fingerprints|fp|db=s' => \@fpdb,
	'h|?|help'               => sub { pod2usage(-verbose => 1) },
	'man'                    => sub { pod2usage(-verbose => 2) },
	'M|merge=s'              => \$merge,
	'n|no-compare'           => \$nocompare,
	'P|prune'                => \$prune,
	'p|program=s'            => \$program,
	'q|quiet'                => sub { $quiet++ },
	'R|recurse'              => \$recurse,
	'r|rescan'               => \$rescan,
	's|script=s'             => \$script,
	't|threshold=s'          => \$threshold,
	'v|verbosity=s'          => \@verbosity,

	'i|include=s'            => \@scriptCode,
	'I|include-file=s'       => \$scriptFile,
) or pod2usage(-verbose => 0);

# ----------------------------------------------------------------------

my @errors = ();
my @warnings = ();

sub exitvalue {
	return(2) if @errors;
	return(1) if @warnings;
	return(0);
}

sub mkerr { push @errors, join("", @_); }
sub mkwarn { push @warnings, join("", @_); }

sub nqprint { print(@_) unless $quiet; }
sub nqwarn { warn("Warning: ", @_) unless $quiet; }
sub nqdie { nqwarn(@_); die; }
sub nqdie2 { warn("Error: ", @_) if $quiet<2; die; }
sub nqexit { warn("Error: ", @_) if $quiet<2; exit(3); }

my $inFP = 0;
$SIG{SEGV} = sub { die $inFP ? "caught segfault" : ()};

sub printScriptFile {
	print("# BEGIN USER FILE INCLUDE\n");
	open(USERSCRIPT, "< $scriptFile") or die("$!\n");
	while (<USERSCRIPT>) {
		chomp;
		print "$_\n";
	}
	close(USERSCRIPT);
	print("# END USER FILE INCLUDE\n\n");
}

# ----------------------------------------------------------------------
#
# setup
#

my ($verb_fp, $verb_md5);

my $read_input = grep(/^-$/, @ARGV);

# XXX: can we tie these to save memory without breaking hv_iterinit() ?
my (%fpcache, %filelist);

my $image = Graphics::Magick->new;

for (@debug) { $debug{$_} = 1 }

map { chomp; $_ .= "\n" } @scriptCode;

if (@scriptCode) {
	unshift(@scriptCode, "# BEGIN USER CODE INCLUDE\n" );
	   push(@scriptCode, "# END USER CODE INCLUDE\n\n" );
}

my $scriptHeader = <<'EOD';
#!/bin/sh

VIEW(){
	echo "$@"
}
END(){
	:;
}

EOD

my $collectionHeader = <<'EOD';
#GQview collection
#created with findimagedupes
# sort: manual
EOD

my $collectionFooter = <<'EOD';
#end
EOD

# ----------------------------------------------------------------------
#
# sanity checks
#

# +----------+
# | warnings |
# +----------+

if ($read_input>1) {
	mkwarn("extra occurrences of \"-\" will be ignored");
}

if ($null and !grep(/^-$/, @ARGV)) {
	mkwarn("--null has no effect in this context");
}

if ($prune and !@fpdb) {
	mkwarn("--prune has no effect in this context");
}

if ($nocompare) {
	mkwarn("--program ignored because --no-compare given") if $program;
	mkwarn("--script ignored because --no-compare given") if $script;
}

if (@warnings and !$quiet) {
	warn( join("\n", map {"Warning: $_"} @warnings), "\n" );
}

# +--------+
# | errors |
# +--------+

if ($collection and -e($collection)) {
	mkerr("Output file for --collection exists: $collection");
}

for (@fpdb) {
	mkerr("File for --fingerprints does not exist: $_")
		unless (-f($_) or (@fpdb==1 and !$merge));
}

if (@fpdb>1 and !$merge) {
	mkerr("Require --merge if using multiple fingerprint databases");
}

# XXX: not sure this is true any more
#if (@fpdb<1 and $merge) {
#	mkerr("Cannot use --merge unless --fingerprints also specified");
#}

if ($merge and -e($merge)) {
	mkerr("Output file for --merge exists: $merge");
}

if ($program) {
	if (! -e($program)) {
		mkerr("File for --program does not exist: $program");
	}
	elsif (! -x($program)) {
		mkerr("File for --program not executable: $program");
	}
}

if ($script and -e($script)) {
	mkerr("Output file for --script exists: $script");
}

if ($scriptFile and !( -f($scriptFile) and -r($scriptFile) )) {
	mkerr("File for --include-file does not exist: $scriptFile");
}

my ($thres_val, $thres_unit) = $threshold =~ m/^\s*(\d+(?:[.]\d+)?)(.*?)\s*$/o;
if ($thres_unit eq '' or $thres_unit eq '%') {
	# percentage to bits
	$threshold = int(2.56 * (100 - $thres_val));
}
elsif ($thres_unit =~ m/^b/oi) {
	# already in bits
	$threshold = int($thres_val);
}
else {
	# error
	$threshold = -1;
}
if ($threshold>256 or $threshold<0) {
	mkerr("--threshold takes values between 0.0% .. 100.0% or 0b .. 256b");
}

for (split(",", join(",", @verbosity))) {
	/^(fingerprint|fp)$/ && do { $verb_fp = 1;  next; };
	/^md5$/              && do { $verb_md5 = 1; next; };
	mkerr("unknown option to --verbosity: $_");
}

if (@errors) {
	exit(exitvalue()) unless $quiet<2;
	pod2usage(
		-verbose => 0,
		-exitval => exitvalue(),
		-msg => join("\n", map {"Error: $_"} @errors),
	);
}

# +-------------------------------------------------+
# | last chance to abort without altering any files |
# +-------------------------------------------------+

unless (@ARGV>0 or @fpdb or $merge) {
	exit(exitvalue()) unless $quiet<2;
	warn("Nothing to do!\n") unless @warnings or $quiet;
	pod2usage(
		-verbose => 0,
		-exitval => exitvalue(),
	);
}

# ----------------------------------------------------------------------
#
# load fingerprint cache
#

for my $db (@fpdb) {
	my %data;
	tie(%data, 'DB_File', $db) or nqexit("tie($db): $!\n");
	while (my ($file, $fp) = each %data) {
		next if ($prune && !-f($file));

		if (exists $fpcache{$file}) {
			# duplicate fingerprint, force regeneration
			delete $fpcache{$file};
		}
		else {
			$fpcache{$file} = $fp;
		}
	}
	untie(%data);
}

# ----------------------------------------------------------------------
#
# build file list
#

my %mergelist;
my $rw = 0;

if ($merge) {
	tie(%mergelist, 'DB_File', $merge) or nqexit("tie($merge): $!\n");
	%mergelist = %fpcache;
	$rw = 1;
}
elsif (@fpdb==1) {
	tie(%mergelist, 'DB_File', $fpdb[0]) or nqexit("tie($fpdb[0]): $!\n");
	%mergelist = %fpcache if $prune;
	$rw = 1;
}

$| = 1;
$/ = "\0" if $null;

for (@ARGV) {
	classify($_);
}

untie(%mergelist);

finddupes() unless $nocompare;

exit 0;

# ----------------------------------------------------------------------

sub process_file {
	my ($path) = @_;
	my $file = realpath($path); # normalize to absolute canonical path
	if (!$file) {
		nqwarn("skipping bogus file: $path\n");
	}
	else {
		my $fp;
		if ($rescan or !exists $fpcache{$file}) {
			$fp = fingerprint($file);
		}
		elsif ($add and exists $fpcache{$file}) {
			$fp = $fpcache{$file};
		}
		if ($fp) {
			$filelist{$file} = $fp;
			delete $fpcache{$file};
			$mergelist{$file} = $filelist{$file} if $rw;
		}

		if ($verb_fp) {
			my $fp = ( $filelist{$file} || $fpcache{$file} );
			if ($fp) {
				print(encode_base64($fp, ""), "  $file\n");
			}
			else {
				nqwarn("can't get fingerprint: $file\n");
			}
		}
		if ($verb_md5) {
			open(FILE, $file) or nqdie2("open($file): $!\n");
			binmode(FILE);
			my $digest = Digest::MD5->new->addfile(*FILE)->hexdigest;
			if ($digest) {
				print("$digest  $file\n");
			}
			else {
				nqwarn("can't get md5sum: $file\n");
			}
			close(FILE);
		}
	}
}

# XXX: This function is complicated by two things:
#	- Historically we didn't recurse and it would be nice to
#		retain nonrecursion as an option.
#	- We need to process "." and ".." when they are given
#		explicitly on the command line.
#	Perhaps we could cleanup the code by rewriting using
#		something like the "-" code?
sub classify {
	my ($file) = @_;

	if ($file eq "-") {
		if ($read_input) {
			$read_input = 0;
			while (<>) {
				chomp;
				classify($_);
			}
		}
		else {
			# silently ignore any extra occurrences of "-"
			# (we already reported them at startup)
		}
	}
	elsif (-d($file) and !-l($file)) {
		# don't follow directory symlinks, to prevent looping
		if (opendir(DIR, $file)) {
			for (readdir(DIR)) {
				my $path = "$file/$_";
				if (-d($path) and !-l($path)) {
					next if m/^\.\.?$/o;	# skip . and ..
					classify($path) if $recurse;
				}
				elsif (-f($path)) {
					process_file($path);
				}
			}
		}
		else {
			nqwarn("can't process directory $file: $@\n");
		}
	}
	elsif (-f($file)) {
		# symlinks are okay for normal files
		process_file($file);
	}
	else {
		# skip anything else (devices, etc)
		nqwarn("skipping file: $file\n");
	}
}

# ----------------------------------------------------------------------

sub try {
	my ($err) = @_;
	if ($err and $err !~ /Warning (315|330):/) {
		die("imagemagick problem: $err\n");
	}
}

sub fingerprint {
	my ($file) = @_;
	my $blob;

	# imagemagick doesn't always catch output from the programs
	# it spawns, so we have to clean up for it...
	open(SAVED_OUT, ">&", \*STDOUT) or nqdie2("open(/dev/null): $!");
	open(SAVED_ERR, ">&", \*STDERR) or nqdie2("open(/dev/null): $!");
	open(STDOUT, ">/dev/null");
	open(STDERR, ">/dev/null");

	$inFP = 1;
	my $result = eval {
		if ((mimetype($file)||'') =~ /^(audio|video)/) {
			die("not fingerprinting A/V file: $file\n");
		}

		if (!$image->Ping($file)) {
			die("not fingerprinting unknown-type file: $file\n");
		}

		try $image->Read($file);

		if ($#$image<0) {
			die("fingerprint: not enough image data for $file");
		}
		else {
			$#$image = 0;
		}
		try $image->Sample("160x160!");
		try $image->Modulate(saturation=>-100);
		try $image->Blur(radius=>3,sigma=>99);
		try $image->Normalize();
		try $image->Equalize();
		try $image->Sample("16x16");
		try $image->Threshold();
		try $image->Set(magick=>'mono');

		($blob) = $image->ImageToBlob();
		if (!defined($blob)) {
			die("This can't happen! undefined blob for: $file\n");
		}
	};

	$inFP = 0;
	@$image = ();

	open(STDOUT, ">&", \*SAVED_OUT) or nqdie2("open(/dev/null): $!");
	open(STDERR, ">&", \*SAVED_ERR) or nqdie2("open(/dev/null): $!");
	close(SAVED_OUT);
	close(SAVED_ERR);

	if (defined $result) {
		return $blob;
	}
	else {
		nqwarn($@);
		return undef;
	}
}

sub finddupes {
	my @matches = findimagedupes::C::diffbits(\%fpcache, \%filelist, $threshold, $add);

	my (%set, %ptr, %val);

	while (@matches) {
		my $a = shift(@matches);
		my $b = shift(@matches);
		my $c = shift(@matches);
		$set{$a} = 1;
		$set{$b} = 1;

		# cf. debian bug #87013

		if (!defined($ptr{$a}) and !defined($ptr{$b})) {
			$ptr{$a} = $a;
			push @{$val{$a}}, $a, $b;
			$ptr{$b} = $a;
			$#{$val{$b}} = 0;
		}
		elsif (defined($ptr{$a}) and !defined($ptr{$b})) {
			push @{$val{$ptr{$a}}}, $b;
			$ptr{$b} = $ptr{$a};
			$#{$val{$b}} = 0;
		}
		elsif (!defined($ptr{$a}) and defined($ptr{$b})) {
			push @{$val{$ptr{$b}}}, $a;
			$ptr{$a} = $ptr{$b};
			$#{$val{$a}} = 0;
		}
		elsif ($ptr{$a} ne $ptr{$b}) {
			my $valptrb = $val{$ptr{$b}};
			push @{$val{$ptr{$a}}}, @{$valptrb};
			for my $bkey (@{$valptrb}) {
				$ptr{$bkey} = $ptr{$a};
			}
			$#$valptrb = 0;
			# else $val{$a} is $val{$b} already
		}
	}

	my $cnt = 0;
	for my $k (keys %filelist, keys %fpcache) {
		$set{$cnt} = $k if defined $set{$cnt};
		$cnt++;
	}

	# FIXME: What is the proper format of collection files?
	#	It seems to be poorly defined, and gthumb parses them
	#	differently from gqview itself. In particular, gthumb
	#	seems to misparse comment lines, and the sort pragma
	#	it defines seems to be fragile wrt whitespace.
	if ($collection) {
		open(COLLECTION, "> $collection") or nqdie2("open(> $collection): $!\n");
		select(COLLECTION);

		print $collectionHeader;
		for my $k (keys %ptr) {
			next unless $ptr{$k} eq $k;
			for ( @{$val{$ptr{$k}}} ) {
				my $name = $set{$_};

				if ( $name =~ /[\n"]/s ) {
					nqwarn("excluded from $collection: $name\n");
				}
				else {
					print qq{"$name"\n};
				}
			}
		}
		print $collectionFooter;
		close(COLLECTION);
	}

	if ($script) {
		open(COMMANDS, "> $script") or nqdie2("open(> $script): $!\n");
	}
	else {
		open(COMMANDS, "| /bin/sh") or nqdie2("open(| /bin/sh): $!\n");
	}
	select(COMMANDS);

	if ($script or $program or !$collection) {
		$program = 'VIEW' unless $program;
		print $scriptHeader;
		printScriptFile if $scriptFile;
		print @scriptCode if @scriptCode;
		for my $k (keys %ptr) {
			next unless $ptr{$k} eq $k;
			print join(" \\\n\t",
				$program,
				( map { quotemeta $set{$_} } @{$val{$ptr{$k}}} ),
				";\n"
			);
		}
		print "\nEND;\n\n";
	}
	close(COMMANDS);
}

# ======================================================================

__DATA__

=head1 NAME

findimagedupes - Finds visually similar or duplicate images

=head1 SYNOPSIS

findimagedupes [option ...] [--] [ - | [file ...] ]

   Options:
      -f, --fingerprints=FILE    -c, --collection=FILE
      -M, --merge=FILE           -p, --program=PROGRAM
      -P, --prune                -s, --script=FILE
      -a, --add                  -i, --include=TEXT
      -r, --rescan               -I, --include-file=FILE
      -n, --no-compare
                                 -q, --quiet
      -t, --threshold=AMOUNT     -v, --verbosity=LIST

      -0, --null                 -h, --help
      -R, --recurse                  --man

With no options, compares the specified files and does not use nor
update any fingerprint database.

Directories of images may be specified instead of individual files;
Sub-directories of these are not searched unless --recurse is used.

=head1 INSTALLATION

If you use linux, your distribution may include a prepackaged version.
For example, Debian and Ubuntu do.

Otherwise, at a minimum you'll need Perl with the modules listed at the
top of the findimagedupes script. Also the GraphicksMagick package.

You may need to change Inline's C<DIRECTORY> to point somewhere else.
Read the Inline module documentation for details.

=head1 OPTIONS

=over 8

=item B<-0>, B<--null>

If a file C<-> is given, a list of files is read from stdin.

Without B<-0>, the list is specified one file per line, such as
produced by find(1) with its C<-print> option.

With B<-0>, the list is expected to be null-delimited, such as
produced by find(1) with its C<-print0> option.

=item B<-a>, B<--add>

Only look for duplicates of files specified on the commandline.

Matches are also sought in any fingerprint databases specified.

=item B<-c>, B<--collection>=I<FILE>

Create GQView collection I<FILE>.gqv of duplicates.

The program attempts to produce well-formed collections.
In particular, it will print a warning and exclude any file
whose name contains newline or doublequote. (In this situation,
gqview(1) seems to create a .gqv collection file that it
silently fails to read back in properly.)

=item B<-d>, B<--debug>=I<OPTS>

Enable debugging output. Options I<OPTS> are subject to change.
See the program source for details.

=item B<-f>, B<--fingerprints>=I<FILE>

Use I<FILE> as fingerprint database.

May be abbreviated as B<--fp> or B<--db>.

This option may be given multiple times when B<--merge> is used.
(Note: I<FILE> could contain commas, so multiple databases may
not be specified as a single comma-delimited list.)

=item B<-h>, B<--help>

Print usage and option sections of this manual.

=item B<-i>, B<--include>=I<TEXT>

I<TEXT> is Bourne-shell code to customise B<--script>.

It is executed after any code included using B<--include-file>.

May be given multiple times. Code will be concatenated.

=item B<-I>, B<--include-file>=I<FILE>

I<FILE> is a file containing Bourne-shell code to customise 
B<--script>. 

It is executed before any code included using B<--include>.

=item B<--man>

Display the full documentation, using default pager.

=item B<--merge>=I<FILE>

Takes any databases specified with B<--fingerprints>
and merges them into a new database called I<FILE>.
Conflicting fingerprints for an image will cause one of two actions to occur:

=over 4

=item 1.

If the image does not exist, then the entry is elided.

=item 2.

If the image does exist, then the old information is ignored
and a new fingerprint is generated from scratch.

=back

By default, image existence is not checked unless there is a conflict.
To force removal of defunct data, use B<--prune> as well.

A list of image files is not required if this option is used.
However, if a list is provided, fingerprint data for the files
will be copied or (re)generated as appropriate.

When B<--merge> is used, the original fingerprint databases are not modified,
even if B<--prune> is used.

See also: B<--rescan>

=item B<-n>, B<--no-compare>

Don't look for duplicates.

=item B<-p>, B<--program>=I<PROGRAM>

Launch I<PROGRAM> (in foreground) to view each set of dupes.

I<PROGRAM> must be the full path to an existing executable file.
For more flexibility, see the B<--include> and B<--include-file>
options.

See also: B<--script>

=item B<--prune>

Remove fingerprint data for images that do not exist any more.
Has no effect unless B<--fingerprints> or B<--merge> is also used.

Databases specified by B<--fingerprints> are only modified if
B<--merge> is not used.

=item B<-q>, B<--quiet>

This option may be given multiple times.

Usually, progress, warning and error messages are printed on stderr.
If this option is given, warnings are not displayed.
If it is given twice or more, errors are not displayed either.

Information requested with B<--verbosity> is still displayed.

=item B<-R>, B<--recurse>

Use B<--recurse> to search recursively for images inside
subdirectories. For historical reasons, the default is to not do so.
To avoid looping, symbolic links to directories are never followed.

=item B<-r>, B<--rescan>

(Re)generate all fingerprints, not just any that are unknown.

If used with B<--add>, only the fingerprints of files specified
on the commandline are (re)generated.

Implies B<--prune>.

=item B<-s>, B<--script>=I<FILE>

When used with B<--program>, I<PROGRAM> is not launched immediately.
Instead sh(1)-style commands are saved to I<FILE>.
This script may be edited (if desired) and then executed manually.

When used without B<--program>, two skeletal shell functions
are generated: C<VIEW> simply echo(1)s its arguments; 
the empty function C<END> runs after files-processing is finished.

To display to terminal (or feed into a pipe), use C<-> as I<FILE>.

If B<--script> is not given, the script is still created in memory and
is executed immediately. So, with the default VIEW and END functions,
lines containing sets of duplicates are displayed. See: B<EXAMPLES>

See also: B<--include>, B<--include-file>

=item B<-t>, B<--threshold>=I<AMOUNT>

Use I<AMOUNT> as threshold of similarity.
Append C<%> to give a percentage or C<b> for bits.
For backwards compatibility, a number with no unit is treated as
a percentage. Percentage is the minimum required for a match;
bits is the maximum that may differ: bits=floor(2.56(100-percent))

A fractional part may be given but it is only accurate to 100/256
(0.390625) for percentage and it is meaningless for C<bits>.
Default is C<90%> (C<25b>) if not specified.

=item B<-v>, B<--verbosity>=I<LIST>

Enable display of informational messages to stdout,
where I<LIST> is a comma-delimited list of:

=over 8

=item B<md5>

Display the checksum for each file, as per md5sum(1).

=item B<fingerprint> | B<fp>

Display the base64-encoded fingerprint of each file.

=back

Alternatively, B<--verbosity> may be given multiple times, and accumulates.
Note that this may not be sensible. For example, to be useful,
B<md5> output probably should not be merged with B<fingerprint> data.

=back

=head1 DESCRIPTION

B<findimagedupes> compares a list of files for visual similarity.

=over 1

=item To calculate an image fingerprint:

 1) Read image.
 2) Resample to 160x160 to standardize size.
 3) Grayscale by reducing saturation.
 4) Blur a lot to get rid of noise.
 5) Normalize to spread out intensity as much as possible.
 6) Equalize to make image as contrasty as possible.
 7) Resample again down to 16x16.
 8) Reduce to 1bpp.
 9) The fingerprint is this raw image data.

=item To compare two images for similarity:

 1) Take fingerprint pairs and xor them.
 2) Compute the percentage of 1 bits in the result.
 3) If percentage exceeds threshold, declare files to be similar.

=back


=head1 RETURN VALUE

=over 4

=item 0

Success.

=item 1

Usage information was requested (B<--help> or B<--man>), or there
were warnings.

=item 2

Invalid options or arguments were provided.

=item 3

Runtime error.

=back

Any other return values indicate an internal error of some sort.

=head1 DIAGNOSTICS

To be written.

=head1 EXAMPLES

=over 4

=item findimagedupes -R -- .

Look for and compare images in all subdirectories of the current directory.

=item find -type f . -print0 | findimagedupes -0 -- -

Same as above.

=item findimagedupes -i 'echo "# sort: manual"' -i 'VIEW(){ for f in "$@";do echo \"file://$f\";done }' -- *.jpg > dupes.gqv

Use script hooks to produce collection-style output
suitable for use with gthumb(1).

=back

=head1 FILES

To be written.

=head1 BUGS

There is a memory leak somewhere.

Killing the programme may corrupt the fingerprint database(s).

Changing version of GraphicsMagick invalidates fingerprint databases.

=head1 NOTES

Directory recursion is deliberately not implemented:
Composing a file-list and using it with C<-> is a more flexible approach.

Repetitions are culled before comparisons take place, so a commandline
like C<findimagedupes a.jpg a.jpg> will not produce a match.

The program needs a lot of memory. Probably not an issue, unless your
machine has less than 128MB of free RAM and you try to compare more than
a hundred-thousand files at once (and the program will run quite slowly
with that many files anyway---about eight hours initially to generate
fingerprints and another ten minutes to do the actual comparing).

=head1 SEE ALSO

find(1), md5sum(1)

B<gqview> - GTK based multiformat image viewer

B<gthumb> - an image viewer and browser for GNOME

=head1 AUTHOR

Jonathan H N Chin <code@jhnc.org>

=head1 COPYRIGHT AND LICENSE

 Copyright 2006-2008 by Jonathan H N Chin <code@jhnc.org>.

 This program is free software; you may redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation; either version 3 of the License, or
 (at your option) any later version.

 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.

 You should have received a copy of the GNU General Public License
 along with this program; if not, write to the Free Software
 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

=head1 HISTORY

This code has been written from scratch. However it owes its existence
to B<findimagedupes> by Rob Kudla and uses the same duplicate-detection
algorithm.

=cut