# -*- coding: utf-8 -*-
"""
Academy Color Encoding System - Input Transform
===============================================
Defines the *Academy Color Encoding System* (ACES) *Input Transform* utilities:
- :func:`colour.spectral_to_aces_relative_exposure_values`
See Also
--------
`RGB Colourspaces Jupyter Notebook
<http://nbviewer.jupyter.org/github/colour-science/colour-notebooks/\
blob/master/notebooks/models/rgb.ipynb>`_
References
----------
- :cite:`TheAcademyofMotionPictureArtsandSciences2014q` : The Academy of
Motion Picture Arts and Sciences, Science and Technology Council, & Academy
Color Encoding System (ACES) Project Subcommittee. (2014). Technical
Bulletin TB-2014-004 - Informative Notes on SMPTE ST 2065-1 - Academy Color
Encoding Specification (ACES). Retrieved from
https://github.com/ampas/aces-dev/tree/master/documents
- :cite:`TheAcademyofMotionPictureArtsandSciences2014r` : The Academy of
Motion Picture Arts and Sciences, Science and Technology Council, & Academy
Color Encoding System (ACES) Project Subcommittee. (2014). Technical
Bulletin TB-2014-012 - Academy Color Encoding System Version 1.0 Component
Names. Retrieved from
https://github.com/ampas/aces-dev/tree/master/documents
- :cite:`TheAcademyofMotionPictureArtsandSciencese` : The Academy of Motion
Picture Arts and Sciences, Science and Technology Council, & Academy Color
Encoding System (ACES) Project Subcommittee. (n.d.). Academy Color Encoding
System. Retrieved February 24, 2014, from
http://www.oscars.org/science-technology/council/projects/aces.html
"""
from __future__ import division, unicode_literals
import numpy as np
from colour.colorimetry import ILLUMINANTS_RELATIVE_SPDS
from colour.models.rgb import ACES_RICD
from colour.utilities import tsplit
__author__ = 'Colour Developers'
__copyright__ = 'Copyright (C) 2013-2018 - Colour Developers'
__license__ = 'New BSD License - http://opensource.org/licenses/BSD-3-Clause'
__maintainer__ = 'Colour Developers'
__email__ = 'colour-science@googlegroups.com'
__status__ = 'Production'
__all__ = [
'FLARE_PERCENTAGE', 'S_FLARE_FACTOR',
'spectral_to_aces_relative_exposure_values'
]
FLARE_PERCENTAGE = 0.00500
S_FLARE_FACTOR = 0.18000 / (0.18000 + FLARE_PERCENTAGE)
[docs]def spectral_to_aces_relative_exposure_values(
spd, illuminant=ILLUMINANTS_RELATIVE_SPDS['D60']):
"""
Converts given spectral power distribution to *ACES2065-1* colourspace
relative exposure values.
Parameters
----------
spd : SpectralPowerDistribution
Spectral power distribution.
illuminant : SpectralPowerDistribution, optional
*Illuminant* spectral power distribution.
Returns
-------
ndarray, (3,)
*ACES2065-1* colourspace relative exposure values array.
Notes
-----
- Output *ACES2065-1* colourspace relative exposure values array is in
range [0, 1].
References
----------
- :cite:`TheAcademyofMotionPictureArtsandSciences2014q`
- :cite:`TheAcademyofMotionPictureArtsandSciences2014r`
- :cite:`TheAcademyofMotionPictureArtsandSciencese`
Examples
--------
>>> from colour import COLOURCHECKERS_SPDS
>>> spd = COLOURCHECKERS_SPDS['ColorChecker N Ohta']['dark skin']
>>> spectral_to_aces_relative_exposure_values(spd) # doctest: +ELLIPSIS
array([ 0.1187697..., 0.0870866..., 0.0589442...])
"""
shape = ACES_RICD.shape
if spd.shape != ACES_RICD.shape:
spd = spd.copy().align(shape)
if illuminant.shape != ACES_RICD.shape:
illuminant = illuminant.copy().align(shape)
spd = spd.values
illuminant = illuminant.values
r_bar, g_bar, b_bar = tsplit(ACES_RICD.values)
def k(x, y):
"""
Computes the :math:`K_r`, :math:`K_g` or :math:`K_b` scale factors.
"""
return 1 / np.sum(x * y)
k_r = k(illuminant, r_bar)
k_g = k(illuminant, g_bar)
k_b = k(illuminant, b_bar)
E_r = k_r * np.sum(illuminant * spd * r_bar)
E_g = k_g * np.sum(illuminant * spd * g_bar)
E_b = k_b * np.sum(illuminant * spd * b_bar)
E_rgb = np.array([E_r, E_g, E_b])
# Accounting for flare.
E_rgb += FLARE_PERCENTAGE
E_rgb *= S_FLARE_FACTOR
return E_rgb