/ 
Image-Hash-0.06
River stage zero No dependents
/ Image::Hash

NAME

Image::Hash - Perceptual image hashing [aHash, dHash, pHash].

SYNOPSIS

use Image::Hash;
use File::Slurp;

# Read a image from the command line
my $image = read_file( shift @ARGV, binmode => ':raw' ) ;

my $ihash = Image::Hash->new($image);

# Calculate the average hash
my $a = $ihash->ahash();

# Calculate the difference hash
my $b = $ihash->dhash();

# Calculate the perception hash
my $p = $ihash->phash();

print "$a\n$b\n$p\n";

DESCRIPTION

Image::Hash allows you to calculate the average hash, difference hash and perception hash an image.

Depending on what is available on your system Image::Hash will use GD, Image::Magick or Imager to interact with your image.

CONSTRUCTOR METHODS

my $ihash = Image::Hash->new($image [, $module ]);

The first argument is a scalar with a binary representation of an image.

You may also optionally specify a second argument of "GD", "ImageMagick" or "Imager" to force Image::Hash to use the specific image module when it interacts with the image. The different image modules may give direct hashes for the same image. Using GD normally hives the best results, and are is highly recommended.

HASHES

ahash

$ihash->ahash();
$ihash->ahash('geometry' => '8x8');

Calculate the Average Hash

Return an array of binary values in array context and a hex representative in scalar context.

dhash

$ihash->dhash();
$ihash->dhash('geometry' => '8x8');

Calculate the Dynamic Hash

Return an array of binary values in array context and a hex representative in scalar context.

phash

$ihash->phash();
$ihash->phash('geometry' => '8x8');

Calculate the Perceptual Hash

Return an array of binary values in array context and a hex representative in scalar context.

HELPER

greytones

$ihash->greytones();
$ihash->greytones('geometry' => '8x8');

Return the number of different shades of grey after the image are converted to grey tones. The number of shades can be used to indicate the complexity of an image, and exclude images that has a very low complexity.

For example, all images with only a single color will be reduced to an image with a single grey color and thus give the same hash.

DEBUGGING

Functions useful for debug purposes.

dump

my $ihash = Image::Hash->new($image, $module);

my @hash = $ihash->ahash();
$ihash->dump('hash' => \@hash );


array(  [ 183 (1), 189 (1), 117 (0),  80 (0), 183 (1), 189 (1), 189 (1), 189 (1) ],
        [ 183 (1), 158 (0),  89 (0), 211 (1),  89 (0), 189 (1), 168 (1), 162 (1) ],
        [ 176 (1), 151 (0),  93 (0), 160 (1), 160 (1), 191 (1), 154 (0), 154 (0) ],
        [ 195 (1), 139 (0),  53 (0), 168 (1),  83 (0), 205 (1), 146 (0), 146 (0) ],
        [ 195 (1), 195 (1), 183 (1), 160 (1), 160 (1), 199 (1), 124 (0), 129 (0) ],
        [ 187 (1), 183 (1), 183 (1), 195 (1), 180 (1), 193 (1), 129 (0), 135 (0) ],
        [ 176 (1), 180 (1), 174 (1), 183 (1), 176 (1), 176 (1), 135 (0), 146 (0) ],
        [ 162 (1), 171 (1),  99 (0), 149 (0), 129 (0), 162 (1), 140 (0), 146 (0) ])

Dump the array used when generating hashes. Option 'hash' may be specified to show with pixel has witch value in the hash.

reducedimage

 use Image::Hash;
 use File::Slurp;

 my $file = shift @ARGV or die("Pleas spesyfi a file to read!");

 my $image = read_file( $file, binmode => ':raw' ) ;

 my $ihash = Image::Hash->new($image);

 binmode STDOUT;
 print STDOUT $ihash->reducedimage();

Returns the reduced image that will be used by the hash functions.

EXAMPLES

Please see the eg/ directory for further examples.

BUGS

Image::Hash support different back ends (GD, Image::Magick or Imager), but because the different back ends work slightly different they will not produce the same hash for the same image. More info is available at https://github.com/runarbu/PerlImageHash/blob/master/Hash_differences.md .

AUTHOR

Runar Buvik
CPAN ID: RUNARB
runarb@gmail.com
http://www.runarb.com

Git

https://github.com/runarbu/PerlImageHash

COPYRIGHT

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

The full text of the license can be found in the LICENSE file included with this module.

SEE ALSO

Articles Looks like it and Kind of like that by Neal Krawetz that describes the theory behind aHash, dHash, pHash.

ImageHash image hashing library written in Python that dos the same thing.

Class ImageHash a PHP class that do the same thing.