def test_images_different_shape(self):
cover_work = Mock(shape=(2, 2))
# watermaked work (stego_work)
ws_work = Mock(shape=(2, 3))
with self.assertRaises(ValueError):
metrics.psnr(cover_work, ws_work)
def pnsr_ber_index(
hider_factory, cover_work, data,
index, step, *args, attacks=None, reference_psnr=44, **kwargs):
def get_extractor(extractor, index):
def wrapper(ws_work):
return extractor(ws_work, index=index)
return wrapper
index = int(round(index))
step = int(round(step))
data = utils.char2bin(data)
hider = hider_factory.build(step, *args, **kwargs)
ws_work = hider.insert(cover_work, data, index=index)
psnr = imperceptibility.psnr(cover_work, ws_work)
watermark = hider.extract(ws_work, index=index)
if attacks:
extract = get_extractor(hider.extract, index)
ber = ber_mean(extract, ws_work, watermark, attacks)
else:
ber = robustness.ber(watermark, data)
return psnr, ber
def test_with_zero_mse(self, mock_mse):
cover_work = np.array([[2.2, 3.3], [5.5, 6.6]])
# watermaked work (stego_work)
ws_work = np.array([[4.4, 7.7], [9.9, 10.0]])
psnr = metrics.psnr(cover_work, ws_work)
np.testing.assert_almost_equal(psnr, 54.151403522, 3)
def test_with_custom_max_value(self, mock_mse):
'''
Testing Peak Signal-to-Noise Ratio (PSNR)
'''
cover_work = Mock()
ws_work = Mock()
psnr = metrics.psnr(cover_work, ws_work, max=200)
np.testing.assert_almost_equal(psnr, 26.020599913, 3)
def test_with_non_zero_mse(self, mock_mse):
'''
Testing Peak Signal-to-Noise Ratio (PSNR)
'''
cover_work = Mock()
ws_work = Mock()
psnr = metrics.psnr(cover_work, ws_work)
np.testing.assert_almost_equal(psnr, 28.130, 3)
def psnr(swarm, cover_work, data, get_ws_work):
'''
psnr(swarm, block, msg) => np.array: return swarm fitness
fitness is related to PSNR metric between cover work an watermarked
(stego) work wich is obtained with (get_ws_work) callback.
This function recive a swarm particle, cover work and data
'''
fitness = np.empty(swarm.shape[0])
for i, particle in enumerate(swarm):
ws_work = (particle, cover_work, data)
try:
psnr = imperceptibility.psnr(cover_work, ws_work)
except:
psnr = 0
finally:
fitness[i] = -psnr
return fitness