def place_pattern(img, pattern_img, pos):
    """
    Place drawn pattern image onto an existing image
    :param img: numpy.ndarray
        The image to draw on.
    :param pattern_img: numpy.ndarray
        Image of the pattern.
    :param pos: tuple
        Contain position on horizontal and vertical axes.
    :return result_img: numpy.ndarray
        The result image.
    """

    x, y = pos
    h, w, _ = pattern_img.shape
    img[y : y+h, x : x+w] = pattern_img

    return img