Rolling block Numpy using strided tricks and padding.

rolling_block.py

import numpy as np
from numpy.lib.stride_tricks import as_strided


def rolling_block(A, block=(3, 3)):
    shape = (A.shape[0] - block[0] + 1, A.shape[1] - block[1] + 1) + block
    strides = (A.strides[0], A.strides[1]) + A.strides
    return as_strided(A, shape=shape, strides=strides)

X = np.random.randint(0, 200, (10, 10))
X = np.pad(X, pad_width=1, mode='constant')
for block in rolling_block(X, (3,3)):
    print(block.sum())



def rolling_block2(A, block=(3, 3)):
    shape = (A.shape[0] - block[0] + 1, A.shape[1] - block[1] + 1) + block
    strides = (A.strides[0], A.strides[1]) + A.strides
    me = 0
    for blocks in as_strided(A, shape=shape, strides=strides):
        for b in blocks:
            mask = np.array([
                [0,1,0],
                [1,0,1],
                [0,1,0]
            ])
            me += (b * mask).sum() * b[1, 1]
    return me