def chunkImageIndices(img):
    """return list of tuples with indices for image chunk"""
    chunksize = (img.shape[0]//2, img.shape[1]//2)

    #list of tuples (begx, endx, begy, endy)
    indices = [(0, chunksize[0], 0, chunksize[1]),
               (chunksize[0], img.shape[0], 0, chunksize[1]),
               (0, chunksize[0], chunksize[1], img.shape[1]),
               (chunksize[0], img.shape[0], chunksize[1], img.shape[1])
               ]
    return indices