def shift_box_down(box, width_step, height_step):
    """Shift box for image cropping to the start of the next row."""
    box_list = list(box)
    box_list[0] = 0
    box_list[1] += height_step
    box_list[2] = width_step
    box_list[3] += height_step
    return tuple(box_list)