Source code for colour.models.aces_rgb_idt

#!/usr/bin/env python
# -*- coding: utf-8 -*-

"""
ACES RGB Colourspace - Input Device Transform
=============================================

Defines the *ACES RGB* colourspace *Input Device Transform* utilities:

-   :func:`spectral_to_aces_relative_exposure_values`

See Also
--------
`RGB Colourspaces IPython Notebook
<http://nbviewer.ipython.org/github/colour-science/colour-ipython/blob/master/notebooks/models/rgb.ipynb>`_  # noqa

References
----------
.. [1]  http://www.oscars.org/science-technology/council/projects/aces.html
        (Last accessed 24 February 2014)
.. [2]  http://www.dropbox.com/sh/iwd09buudm3lfod/gyjDF-k7oC/ACES_v1.0.1.pdf
        (Last accessed 24 February 2014)
"""

from __future__ import division, unicode_literals

import numpy as np

from colour.colorimetry import ILLUMINANTS_RELATIVE_SPDS
from colour.models import ACES_RICD

__author__ = 'Colour Developers'
__copyright__ = 'Copyright (C) 2013 - 2014 - 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.get('D60')): """ Converts given spectral power distribution to *ACES RGB* colourspace relative exposure values. Parameters ---------- spd : SpectralPowerDistribution Spectral power distribution. illuminant : SpectralPowerDistribution, optional *Illuminant* spectral power distribution. Returns ------- ndarray, (3,) *ACES RGB* colourspace relative exposure values matrix. Notes ----- - Output *ACES RGB* colourspace relative exposure values matrix is in domain [0, 1]. See Also -------- :func:`colour.colorimetry.tristimulus.spectral_to_XYZ` References ---------- 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.clone().align(shape) if illuminant.shape != ACES_RICD.shape: illuminant = illuminant.clone().align(shape) spd = spd.values illuminant = illuminant.values r_bar, g_bar, b_bar = (ACES_RICD.r_bar.values, ACES_RICD.g_bar.values, ACES_RICD.b_bar.values) k = lambda x, y: 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