An example of how perceptual hashes change at various settings when one pixel changes

change_demo.py

from PIL import Image
import imagehash
from pathlib import Path
from hashlib import sha256

PWD = (Path(__file__).resolve()).parent


demo1 = PWD / "demo1.bmp"
demo2 = PWD / "demo2.bmp"

hash_size = 8

for algo in (
    imagehash.phash,
    imagehash.dhash,
    imagehash.average_hash,
    imagehash.whash,
):
    print("\nHash:", str(algo), "/ Hash size:", hash_size)

    hash1 = algo(Image.open(demo1), hash_size=hash_size)
    hash2 = algo(Image.open(demo2), hash_size=hash_size)

    with demo1.open("rb") as f:
        sha256hash1 = sha256(f.read()).hexdigest()
    with demo2.open("rb") as f:
        sha256hash2 = sha256(f.read()).hexdigest()

    print(demo1.name, sha256hash1[:10], hash1)
    print(demo2.name, sha256hash2[:10], hash2)

    print(demo1.name, "-", demo2.name, "=", (hash1 - hash2))

hash_comparison_size32.txt

❯ poetry run python change_demo.py
Using python3.7 (3.7.10)

Hash: <function phash at 0x11662ca70> / Hash size: 32
demo1.bmp c8b02cc822 8000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
demo2.bmp 8b345271bb ccccccc68cccc6663333333933333999ccccccc6ccccc6663333333933333999ccccccc6ccccc6663333333933333999ccccccc6ccccc6663333333933333999ccccccc6ccccc6663333333933333999ccccccc6cccce6663333333933331999ccccccc6cccce6663333333933331999ccccccc6cccce6663333333933339999
demo1.bmp - demo2.bmp = 511

Hash: <function dhash at 0x1166545f0> / Hash size: 32
demo1.bmp c8b02cc822 0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
demo2.bmp 8b345271bb 0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
demo1.bmp - demo2.bmp = 0

Hash: <function average_hash at 0x116628f80> / Hash size: 32
demo1.bmp c8b02cc822 0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
demo2.bmp 8b345271bb 0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
demo1.bmp - demo2.bmp = 0

Hash: <function whash at 0x1166d7a70> / Hash size: 32
demo1.bmp c8b02cc822 0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
demo2.bmp 8b345271bb ffff0000ffff0000ffff0000ffff0000ffff0000ffff0000ffff0000ffff0000ffff0000ffff0000ffff0000ffff0000ffff0000ffff0000ffff0000ffff0000ffff0000ffff0000ffff0000ffff0000ffff0000ffff0000ffff0000ffff0000ffff0000ffff0000ffff0000ffff0000ffff0000ffff0000ffff0000ffff0000
demo1.bmp - demo2.bmp = 512

hash_comparison_size64.txt

❯ poetry run python change_demo.py
Using python3.7 (3.7.10)

Hash: <function phash at 0x11164ea70> / Hash size: 64
demo1.bmp c8b02cc822 8000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
demo2.bmp 8b345271bb ccccccc66666663333333339999999cc33333339999999ccccccccc666666633ccccccc66666663333333339999999cc33333339999999ccccccccc666666633ccccccc66666663333333339999999cc33333339999999ccccccccc666666633ccccccc66666663333333339999999cc33333339999999ccccccccc666666633ccccccc66666663333333339999999cc33333339999999ccccccccc666666633ccccccc66666663333333339999999cc33333339999999ccccccccc666666633ccccccc66666663333333339999999cc33333339999999ccccccccc666666633ccccccc66666663333333339999999cc33333339999999ccccccccc666666633ccccccc66666663333333339999999cc33333339999999ccccccccc666666633ccccccc66666663333333339999999cc33333339999999ccccccccc666666633ccccccc66666663333333339999999cc33333339999999ccccccccc666666633ccccccc66666663333333339999999cc33333339999999ccccccccc666666633ccccccc66666663333333339999999cc33333339999999ccccccccc666666633ccccccc66666663333333339999999cc33333339999999ccccccccc666666633ccccccc66666663333333339999999cc33333339999999ccccccccc666666633ccccccc66666663333333339999999cc33333339999999ccccccccc666666633
demo1.bmp - demo2.bmp = 2047

Hash: <function dhash at 0x1116765f0> / Hash size: 64
demo1.bmp c8b02cc822 0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
demo2.bmp 8b345271bb 0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000020000000000000002000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
demo1.bmp - demo2.bmp = 2

Hash: <function average_hash at 0x11164af80> / Hash size: 64
demo1.bmp c8b02cc822 0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
demo2.bmp 8b345271bb 0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000002000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
demo1.bmp - demo2.bmp = 1

Hash: <function whash at 0x1116faa70> / Hash size: 64
demo1.bmp c8b02cc822 0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
demo2.bmp 8b345271bb ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000fffffffe00000000fffffffe00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff00000000
demo1.bmp - demo2.bmp = 2046

hash_comparison_size8.txt

❯ poetry run python change_demo.py
Using python3.7 (3.7.10)

Hash: <function phash at 0x10dbbfa70> / Hash size: 8
demo1.bmp c8b02cc822 8000000000000000
demo2.bmp 8b345271bb 8000000000000000
demo1.bmp - demo2.bmp = 0

Hash: <function dhash at 0x10dbe75f0> / Hash size: 8
demo1.bmp c8b02cc822 0000000000000000
demo2.bmp 8b345271bb 0000000000000000
demo1.bmp - demo2.bmp = 0

Hash: <function average_hash at 0x10dbbaf80> / Hash size: 8
demo1.bmp c8b02cc822 0000000000000000
demo2.bmp 8b345271bb 0000000000000000
demo1.bmp - demo2.bmp = 0

Hash: <function whash at 0x10dc6aa70> / Hash size: 8
demo1.bmp c8b02cc822 0000000000000000
demo2.bmp 8b345271bb f0f0f0f0f0f0f0f0
demo1.bmp - demo2.bmp = 32

Images used: