def test_centroid(self):
"""Test :func:`colour.utilities.array.centroid` definition."""
a = np.arange(5)
np.testing.assert_array_equal(centroid(a), np.array([3]))
a = np.tile(a, (5, 1))
np.testing.assert_array_equal(centroid(a), np.array([2, 3]))
a = np.tile(np.linspace(0, 1, 10), (10, 1))
np.testing.assert_array_equal(centroid(a), np.array([4, 6]))
a = tstack([a, a, a])
np.testing.assert_array_equal(centroid(a), np.array([4, 6, 1]))
def luminance_variance(a):
"""
Computes the Luminance variance of given :math:`a` 2-D array.
Parameters
----------
a : array_like
:math:`a` 2-D array to compute the Luminance variation.
Returns
-------
numeric
:math:`a` 2-D array Luminance variance.
Examples
--------
>>> a = np.tile(np.arange(5), (5, 1))
>>> luminance_variance(a) # doctest: +ELLIPSIS
12.2474487...
"""
x, y = np.mgrid[0:np.shape(a)[0], 0:np.shape(a)[1]]
x_centroid, y_centroid = centroid(a)
variance = np.sqrt(np.sum(a * ((y - y_centroid)**2 + (x - x_centroid)**2)))
return variance
def test_centroid(self):
"""
Tests :func:`colour.utilities.array.centroid` definition.
"""
a = np.arange(5)
np.testing.assert_array_equal(centroid(a), np.array([3]))
a = np.tile(a, (5, 1))
np.testing.assert_array_equal(centroid(a), np.array([2, 3]))
a = np.tile(np.linspace(0, 1, 10), (10, 1))
np.testing.assert_array_equal(centroid(a), np.array([4, 6]))
a = tstack([a, a, a])
np.testing.assert_array_equal(centroid(a), np.array([4, 6, 1]))
def light_probe_sampling_variance_minimization_Viriyothai2009(
light_probe, lights_count=16, colourspace=RGB_COLOURSPACES['sRGB']):
"""
Sample given light probe to find lights using *Viriyothai (2009)* variance
minimization light probe sampling algorithm.
Parameters
----------
light_probe : array_like
Array to sample for lights.
lights_count : int
Amount of lights to generate.
colourspace : `colour.RGB_Colourspace`, optional
*RGB* colourspace used for internal *Luminance* computation.
Returns
-------
list
list of
:class:`colour_hdri.sampling.variance_minimization.Light_Specification`
lights.
References
----------
:cite:`Viriyothai2009`
"""
light_probe = as_float_array(light_probe)
iterations = np.sqrt(lights_count).astype(np.int_)
if iterations**2 != lights_count:
warning(
'{0} lights requested, {1} will be effectively computed!'.format(
lights_count, iterations**2))
Y = RGB_luminance(light_probe, colourspace.primaries,
colourspace.whitepoint)
regions = find_regions_variance_minimization_Viriyothai2009(Y, iterations)
lights = []
for region in regions:
y_min, y_max, x_min, x_max = region
c = centroid(Y[y_min:y_max, x_min:x_max])
c = (c + np.array([y_min, x_min]))
light_probe_c = light_probe[y_min:y_max, x_min:x_max]
lights.append(
Light_Specification((c / np.array(Y.shape))[::-1],
np.sum(np.sum(light_probe_c, 0), 0), c))
return lights