def test_png_gen_greyscale_works():
alpha_ch = np.array([[1, 1, 1]])
gen = PngGenerator(alpha_ch, greyscale=True)
img_data = np.array([[0.0, 5.0, 10.0]])
norm_img_data = (img_data - img_data.min()) / (img_data.max() -
img_data.min())
img_bytes = gen.generate_png(img_data)
reader = Reader(bytes=img_bytes)
width, height, pixels, _ = reader.asFloat()
assert_equal(width, 3)
assert_equal(height, 1)
grey_shape = img_data.shape + (2, )
assert_almost_equal(np.array(list(pixels)).reshape(grey_shape)[:, :, 0],
norm_img_data,
decimal=4)
