Way to compare image hashes

[benkasminbullock]

At the moment the module returns image hashes but it doesn't seem to offer a way to compare the hashes of two different images. I request adding the feature of a simple way of comparing images.

[runarbu]

There are currently two ways to compare the hashes. If they are totally equal you can just do a 'eq', but the hashes rarely are totally equal.

If the hash is slightly different you need to compare the Hamming distance like this:

    # Hamming distance. Take two hashes in. 
    # Returns the distance. If distance is below 5 the image is normally equal
    sub hammingdistance {
            my ($a, $b) = @_;

            my $distance = 0;
            for (my $i = 0; $i < 64; $i++) {
                    if ($a->{'hash'}->[$i] != $b->{'hash'}->[$i]) {
                            $distance++;
                    }
    
            }

            return $distance;
    }

The hammingdistance function sold definitely be added and this better documented.

Does this clarifies it, or did you mean on some other way of comparing images?

[benkasminbullock]

I think casual users of the module would find the module much more useful if there was a simple way to compare the hashes, or even an example in the documentation of how to compare the hashes.

[runarbu]

I agree, you are right. The hammingdistance function sold definitely be added and better documented.

Casual users may also be interested in using the hammingdistance function together with Tree::BK to easily do fuzzy matching on a large set of images, so that should be documented too.

[benkasminbullock]

If there is anything I can do to assist in getting this done, let me know.