def test_n_dimensional_gamma_function(self):
"""
Tests :func:`colour.models.rgb.transfer_functions.gamma.\
gamma_function` definition n-dimensional arrays support.
"""
a = 0.18
a_p = 0.022993204992707
np.testing.assert_almost_equal(
gamma_function(a, 2.2),
a_p,
decimal=7)
a = np.tile(a, 6)
a_p = np.tile(a_p, 6)
np.testing.assert_almost_equal(
gamma_function(a, 2.2),
a_p,
decimal=7)
a = np.reshape(a, (2, 3))
a_p = np.reshape(a_p, (2, 3))
np.testing.assert_almost_equal(
gamma_function(a, 2.2),
a_p,
decimal=7)
a = np.reshape(a, (2, 3, 1))
a_p = np.reshape(a_p, (2, 3, 1))
np.testing.assert_almost_equal(
gamma_function(a, 2.2),
a_p,
decimal=7)
def test_n_dimensional_gamma_function(self):
"""
Tests :func:`colour.models.rgb.transfer_functions.gamma.\
gamma_function` definition n-dimensional arrays support.
"""
a = 0.18
a_p = 0.022993204992707
np.testing.assert_almost_equal(
gamma_function(a, 2.2),
a_p,
decimal=7)
a = np.tile(a, 6)
a_p = np.tile(a_p, 6)
np.testing.assert_almost_equal(
gamma_function(a, 2.2),
a_p,
decimal=7)
a = np.reshape(a, (2, 3))
a_p = np.reshape(a_p, (2, 3))
np.testing.assert_almost_equal(
gamma_function(a, 2.2),
a_p,
decimal=7)
a = np.reshape(a, (2, 3, 1))
a_p = np.reshape(a_p, (2, 3, 1))
np.testing.assert_almost_equal(
gamma_function(a, 2.2),
a_p,
decimal=7)
def test_nan_gamma_function(self):
"""
Tests :func:`colour.models.rgb.transfer_functions.gamma.\
gamma_function` definition nan support.
"""
cases = [-1.0, 0.0, 1.0, -np.inf, np.inf, np.nan]
for case in cases:
gamma_function(case, case)
def test_gamma_function(self):
"""
Tests :func:`colour.models.rgb.transfer_functions.gamma.\
gamma_function` definition.
"""
self.assertAlmostEqual(gamma_function(0.0, 2.2), 0.0, places=7)
self.assertAlmostEqual(gamma_function(0.18, 2.2),
0.022993204992707,
places=7)
self.assertAlmostEqual(gamma_function(0.022993204992707, 1.0 / 2.2),
0.18,
places=7)
def oetf_ARIBSTDB67(E, r=0.5, constants=ARIBSTDB67_CONSTANTS):
"""
Defines *ARIB STD-B67 (Hybrid Log-Gamma)* opto-electrical transfer
function (OETF / OECF).
Parameters
----------
E : numeric or array_like
Voltage normalised by the reference white level and proportional to
the implicit light intensity that would be detected with a reference
camera color channel R, G, B.
r : numeric, optional
Video level corresponding to reference white level.
constants : Structure, optional
*ARIB STD-B67 (Hybrid Log-Gamma)* constants.
Returns
-------
numeric or ndarray
Resulting non-linear signal :math:`E'`.
Notes
-----
+------------+-----------------------+---------------+
| **Domain** | **Scale - Reference** | **Scale - 1** |
+============+=======================+===============+
| ``E`` | [0, 1] | [0, 1] |
+------------+-----------------------+---------------+
+------------+-----------------------+---------------+
| **Range** | **Scale - Reference** | **Scale - 1** |
+============+=======================+===============+
| ``E_p`` | [0, 1] | [0, 1] |
+------------+-----------------------+---------------+
- This definition uses the *mirror* negative number handling mode of
:func:`colour.models.gamma_function` definition to the sign of negative
numbers.
References
----------
:cite:`AssociationofRadioIndustriesandBusinesses2015a`
Examples
--------
>>> oetf_ARIBSTDB67(0.18) # doctest: +ELLIPSIS
0.2121320...
"""
E = to_domain_1(E)
a = constants.a
b = constants.b
c = constants.c
E_p = np.where(E <= 1, r * gamma_function(E, 0.5, 'mirror'),
a * np.log(E - b) + c)
return as_float(from_range_1(E_p))
def test_gamma_function(self):
"""
Tests :func:`colour.models.rgb.transfer_functions.gamma.\
gamma_function` definition.
"""
self.assertAlmostEqual(
gamma_function(0.0, 2.2),
0.0,
places=7)
self.assertAlmostEqual(
gamma_function(0.18, 2.2),
0.022993204992707,
places=7)
self.assertAlmostEqual(
gamma_function(0.022993204992707, 1.0 / 2.2),
0.18,
places=7)
def test_gamma_function(self):
"""
Tests :func:`colour.models.rgb.transfer_functions.gamma.\
gamma_function` definition.
"""
self.assertAlmostEqual(
gamma_function(0.0, 2.2),
0.0,
places=7)
self.assertAlmostEqual(
gamma_function(0.18, 2.2),
0.022993204992707,
places=7)
self.assertAlmostEqual(
gamma_function(0.022993204992707, 1.0 / 2.2),
0.18,
places=7)
self.assertAlmostEqual(
gamma_function(-0.18, 2.0),
0.0323999999999998,
places=7)
np.testing.assert_array_equal(
gamma_function(-0.18, 2.2),
np.nan)
self.assertAlmostEqual(
gamma_function(-0.18, 2.2, 'Mirror'),
-0.022993204992707,
places=7)
self.assertAlmostEqual(
gamma_function(-0.18, 2.2, 'Preserve'),
-0.18,
places=7)
self.assertAlmostEqual(
gamma_function(-0.18, 2.2, 'Clamp'),
0,
places=7)
def oetf_inverse_ARIBSTDB67(E_p, r=0.5, constants=ARIBSTDB67_CONSTANTS):
"""
Defines *ARIB STD-B67 (Hybrid Log-Gamma)* inverse opto-electrical transfer
function (OETF / OECF).
Parameters
----------
E_p : numeric or array_like
Non-linear signal :math:`E'`.
r : numeric, optional
Video level corresponding to reference white level.
constants : Structure, optional
*ARIB STD-B67 (Hybrid Log-Gamma)* constants.
Returns
-------
numeric or ndarray
Voltage :math:`E` normalised by the reference white level and
proportional to the implicit light intensity that would be detected
with a reference camera color channel R, G, B.
Notes
-----
+------------+-----------------------+---------------+
| **Domain** | **Scale - Reference** | **Scale - 1** |
+============+=======================+===============+
| ``E_p`` | [0, 1] | [0, 1] |
+------------+-----------------------+---------------+
+------------+-----------------------+---------------+
| **Range** | **Scale - Reference** | **Scale - 1** |
+============+=======================+===============+
| ``E`` | [0, 1] | [0, 1] |
+------------+-----------------------+---------------+
- This definition uses the *mirror* negative number handling mode of
:func:`colour.models.gamma_function` definition to the sign of negative
numbers.
References
----------
:cite:`AssociationofRadioIndustriesandBusinesses2015a`
Examples
--------
>>> oetf_inverse_ARIBSTDB67(0.212132034355964) # doctest: +ELLIPSIS
0.1799999...
"""
E_p = to_domain_1(E_p)
a = constants.a
b = constants.b
c = constants.c
with domain_range_scale('ignore'):
E = np.where(
E_p <= oetf_ARIBSTDB67(1),
gamma_function((E_p / r), 2, 'mirror'),
np.exp((E_p - c) / a) + b,
)
return as_float(from_range_1(E))
def test_gamma_function(self):
"""
Tests :func:`colour.models.rgb.transfer_functions.gamma.\
gamma_function` definition.
"""
self.assertAlmostEqual(gamma_function(0.0, 2.2), 0.0, places=7)
self.assertAlmostEqual(
gamma_function(0.18, 2.2), 0.022993204992707, places=7)
self.assertAlmostEqual(
gamma_function(0.022993204992707, 1.0 / 2.2), 0.18, places=7)
self.assertAlmostEqual(
gamma_function(-0.18, 2.0), 0.0323999999999998, places=7)
np.testing.assert_array_equal(gamma_function(-0.18, 2.2), np.nan)
self.assertAlmostEqual(
gamma_function(-0.18, 2.2, 'Mirror'), -0.022993204992707, places=7)
self.assertAlmostEqual(
gamma_function(-0.18, 2.2, 'Preserve'), -0.18, places=7)
self.assertAlmostEqual(
gamma_function(-0.18, 2.2, 'Clamp'), 0, places=7)
np.testing.assert_array_equal(gamma_function(-0.18, -2.2), np.nan)
self.assertAlmostEqual(
gamma_function(0.0, -2.2, 'Mirror'), 0.0, places=7)
self.assertAlmostEqual(
gamma_function(0.0, 2.2, 'Preserve'), 0.0, places=7)
self.assertAlmostEqual(gamma_function(0.0, 2.2, 'Clamp'), 0, places=7)