phashbench.py

import numpy, math

N = 32 # image size
M = 8 # number of DCT coefficients

def dcthash(data):
    k = math.sqrt(2.0 / N)
    dct_k = numpy.matrix([
        [k * math.cos((math.pi / 2 / N) * y * (2 * x + 1)) for x in range(N)]
        for y in range(M)
    ])
    dct_k_t = numpy.transpose(dct_k)

    coefs = numpy.array(dct_k * data * dct_k_t).flatten()
    h = sum((1<<i) for i,j in enumerate(coefs) if j > 0)

    return h

if __name__ == "__main__":
    import sys
    from PIL import Image
    im = Image.open(sys.argv[1])

    rim = im.convert("L").resize((N, N), resample=Image.BILINEAR)
    data = numpy.array(rim)
    print("%016x" % dcthash(data))

    import timeit
    t=timeit.timeit(lambda: im.convert("L").resize((N, N), resample=Image.BILINEAR), number=1000)
    print(f"Resize: {1000/t}/sec")


    t2=timeit.timeit(lambda: dcthash(data), number=1000)
    print(f"Hash: {1000/t2}/sec")