Using OpenCV's Image Hashing Module from Python

Question

I want to use OpenCV's perceptual hashing functions from Python.

This isn't working.

import cv2
a_1 = cv2.imread('a.jpg')
cv2.img_hash_BlockMeanHash.compute(a_1)

I get:

TypeError: descriptor 'compute' requires a 'cv2.img_hash_ImgHashBase' object but received a 'numpy.ndarray'

And this is failing too

a_1_base = cv2.img_hash_ImgHashBase(a_1) 
cv2.img_hash_BlockMeanHash.compute(a_1_base)

I get:

TypeError: Incorrect type of self (must be 'img_hash_ImgHashBase' or its derivative)

Colab notebook showing this:

https://colab.research.google.com/drive/1x5ZxMBD3wFts2WKS4ip3rp4afDx0lGhi

Take a look at this: pyimagesearch.com/2017/11/27/image-hashing-opencv-python — xilpex
– xilpex, Commented Apr 21, 2019 at 14:57

stav · Accepted Answer · 2019-04-21 20:29:03Z

14

+50

It's a common compatibility gap that the OpenCV python interface has with the C++ interface (i.e. the classes don't inherit from each other the same way). There are the *_create() static functions for that.

So you should use:

hsh = cv2.img_hash.BlockMeanHash_create()
hsh.compute(a_1)

In a copy of your collab notebook: https://colab.research.google.com/drive/1CLJNPPbeO3CiQ2d8JgPxEINpr2oNMWPh#scrollTo=OdTtUegmPnf2

answered Apr 21, 2019 at 20:29

stav

1,8352 gold badges21 silver badges43 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

user2809176 Over a year ago

it returns an array, how to get one number?

user2809176 Over a year ago

hash_xor = reduce(lambda x, y: x ^ y, hash[0]) ?

Dandelion Over a year ago

It gives me following error: AttributeError: module 'cv2.cv2' has no attribute 'img_hash'. My opencv-python and opencv-contrib-python version is 4.3.0

Dandelion Over a year ago

Removing opencv-python and reinstalling it, solved the isuue!

whomm · Accepted Answer · 2019-07-16 09:55:02Z

11

pip install opencv-python
pip install opencv-contrib-python    #img_hash in this one

(https://pypi.org/project/opencv-python/)

answered Jul 16, 2019 at 9:55

whomm

1231 silver badge5 bronze badges

1 Comment

cards Jul 17 at 13:35

pip uninstall opencv-python, never both together!

A. Genchev · Accepted Answer · 2021-04-15 20:46:05Z

7

Here I show you how to compute 64-bit pHash with OpenCV. I defined a function which returns unsigned, 64-bit integer pHash from a color BGR cv2 image passed-in:

import cv2
    
def pHash(cv_image):
        imgg = cv2.cvtColor(cv_image, cv2.COLOR_BGR2GRAY);
        h=cv2.img_hash.pHash(imgg) # 8-byte hash
        pH=int.from_bytes(h.tobytes(), byteorder='big', signed=False)
        return pH

You need to have installed and import cv2 for this to work.

edited Apr 15, 2021 at 20:46

answered Jan 24, 2021 at 1:28

A. Genchev

4394 silver badges7 bronze badges

1 Comment

Dominik Sajovic Over a year ago

Is there a way to generate larger than 8-byte hash? for example 16-byte.

Collectives™ on Stack Overflow

Using OpenCV's Image Hashing Module from Python

3 Answers 3

4 Comments

1 Comment

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

4 Comments

1 Comment

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related