This Julia library aims to implement a range of perceptual hashing techniques.
Perceptual hashing is the process of generating a hash value for an image (or more abstractly, a video or audio file) which represents the essential qualities of the file regarding properties which are important to a human observer. For example, comparing an image X with a compressed version of the image x should result in the same or highly similar hash values. This is in contrast to non-perceptual hashing techniques such as MD5 or SHA-1, which are sensitive to imperceptible changes in the file.
Perceptual hashing is a useful tool for detecting duplicates of images which are intentionally or accidentally transformed in imperceptible ways.
This library currently implements:
- The Block Mean Value hash described by Zauner (2010)
- The Discrete Cosine Transform hash described by the same.
Usage is simple.
using PerceptualHashes
# Hash an image identified by its filename.
a_hash = perceptual_hash("images/architecture1.bmp")
b_hash = perceptual_hash("images/architecture1-compressed.jpg")
c_hash = perceptual_hash("images/doodle.bmp")
# Compare images with their hash Hamming distance
hdist(a_hash, b_hash)
# 4 low value, some compression impact.
hdist(a_hash, c_hash)
# 122 high value, totally different image.
There is also a library function to resolve all images in a given directory.
# Call with a directory name and a 'tolerance' value for image similarity (default=0)
resolve_images("images", 5)
#Dict{Any,Any} with 16 entries:
# "images//diamondskull-compressed.jpg" => Any["images//diamondskull.bmp"]
# "images//england.bmp" => Any["images//england-compressed.jpg"]
# "images//bamarket115.bmp" => Any["images//bamarket115-compressed.jpg"]
# "images//doodle-compressed.jpg" => Any["images//doodle.bmp"]
# "images//doodle.bmp" => Any["images//doodle-compressed.jpg"]
# "images//england-compressed.jpg" => Any["images//england.bmp"]
# "images//architecture_2-compressed.jpg" => Any["images//architecture_2.bmp"]
# "images//bamarket115-compressed.jpg" => Any["images//bamarket115.bmp"]
# "images//architecture1.bmp" => Any["images//architecture1-compressed.jpg"]
# "images//architecture_2.bmp" => Any["images//architecture_2-compressed.jpg"]
# "images//wallacestevens-compressed.jpg" => Any["images//wallacestevens.bmp"]
# "images//englandpath-compressed.jpg" => Any["images//englandpath.bmp"]
# "images//wallacestevens.bmp" => Any["images//wallacestevens-compressed.jpg"]
# "images//architecture1-compressed.jpg" => Any["images//architecture1.bmp"]
# "images//diamondskull.bmp" => Any["images//diamondskull-compressed.jpg"]
# "images//englandpath.bmp" => Any["images//englandpath-compressed.jpg"]