im2col.py

#from https://gist.githubusercontent.com/anirudhshenoy/d4e4228ebb884066efd65299f1d169cb/raw/bbe787ecbcf014e6e64e0ee8b9217923167c626d/naive_im2col.py
def im2col(x, kernel):
    kernel_shape = kernel.shape[0]
    rows = []
    
    # Assuming Padding = 0, stride = 1
    for row in range(x.shape[0] - 1):
        for col in range(x.shape[1] - 1):
            window = x[row: row + kernel_shape, col: col + kernel_shape]
            rows.append(window.flatten())
            
    return np.transpose(np.array(rows))