def prepare_grid(window_size: float, nb_pixels: int) -> numpy.ndarray:
    x = numpy.linspace(-window_size, window_size, nb_pixels)
    x = x.reshape((nb_pixels, 1))
    y = numpy.linspace(-window_size, window_size, nb_pixels)
    y = y.reshape((1, nb_pixels))
    return x + 1.0j * y