This Ruby gem is made for image simularity comparison, using the C libary libpuzzle.
Install
gem install libpuzzle
Make sure you have installed libpuzzle (>= 0.11) first.
Install Libpuzzle
Homebrew:
brew install libpuzzle
APT:
apt-get install libpuzzle1 libpuzzle-dev
Compile:
sudo apt-get install -qq libgd2-xpm-dev
wget http://download.pureftpd.org/pub/pure-ftpd/misc/libpuzzle/releases/libpuzzle-0.11.tar.bz2
tar -xvj -f libpuzzle-0.11.tar.bz2
cd libpuzzle-0.11 && ./configure && make && sudo make install
Since the object file is located in /usr/local/lib, you might want to export LD_LIBRARY_PATH before gem installation, for example:
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/local/lib
gem install libpuzzle
Usage
# load image
p1 = Puzzle.new('foo.png')
p2 = Puzzle.new('bar.png')
p1.similar? p2 # default threshold is 0.6
p1.similar? p2, threshold: 0.7
# get exact distance
p1.distance p2
# compress
p1.compress # => compressed string
# uncompress
Puzzle.uncompress 'COMPRESSED_STRING' # => #<Puzzle>Integrate with ActiveRecord
Follow the naming convention of ActiveRecord, the database schema will look like:
+---------------------------------+
| signatures |
+---------------------------------+
| id | signature | picture_id |
+--------+-----------+------------+
+-------------------------------------+
| words |
+-------------------------------------+
| id | position | word | signature_id |
+----+----------+------+--------------+
class Word < ActiveRecord::Base
belongs_to :signature
end
class Signature < ActiveRecord::Base
K, N = 10, 100
has_many :words
def cut_vectors_into_words!
puzzle = Puzzle.uncompress signature
i = 0
while i < N && word = puzzle.vector.byteslice(i, K)
words.find_or_create_by! word: word, position: i
i += 1
end
end
def similar_signatures
Signature.distinct.joins(:words)
.where('EXISTS (SELECT * FROM words AS _words WHERE _words.sig_id = ? AND _words.position = words.position and _words.word = words.word)', id)
.where.not(id: id)
.select{ |sig| Puzzle.uncompress(sig.signature) == Puzzle.uncompress(signature) }
end
end