[Masked window from numpy array] #numpy #algorithms

extract_masked_window.py

import numpy.ma as ma


def extract_masked_window(arr, mask, offset=(0, 0)):
    """
    Extract the (possibly) masked window from a numpy array

    Parameters
    ----------
    arr : array-like
        The array from which to extract 
    mask : array-like, boolean
        The mask to extract.  Note that values to extract are marked as True
        and values to ignore are marked as False.
    offset : tuple
        Row and column offsets into the array

    Returns
    -------
    ret : masked array
        The masked subset window
    """
    #TODO: Needs a lot more error checking and tests
    r, c = offset
    h, w = mask.shape
    return ma.masked_array(arr[r:r+h, c:c+w], mask=~mask)