Source code for colour.models.hdr_ipt

"""
Hdr-IPT Colourspace
===================

Defines the *hdr-IPT* colourspace transformations:

-   :attr:`colour.HDR_IPT_METHODS`: Supported *hdr-IPT* colourspace computation
    methods.
-   :func:`colour.XYZ_to_hdr_IPT`
-   :func:`colour.hdr_IPT_to_XYZ`

References
----------
-   :cite:`Fairchild2010` : Fairchild, M. D., & Wyble, D. R. (2010). hdr-CIELAB
    and hdr-IPT: Simple Models for Describing the Color of High-Dynamic-Range
    and Wide-Color-Gamut Images. Proc. of Color and Imaging Conference,
    322-326. ISBN:978-1-62993-215-6
-   :cite:`Fairchild2011` : Fairchild, M. D., & Chen, P. (2011). Brightness,
    lightness, and specifying color in high-dynamic-range scenes and images. In
    S. P. Farnand & F. Gaykema (Eds.), Proc. SPIE 7867, Image Quality and
    System Performance VIII (p. 78670O). doi:10.1117/12.872075
"""

from __future__ import annotations

import numpy as np

from colour.algebra import vector_dot
from colour.colorimetry import (
    lightness_Fairchild2010,
    lightness_Fairchild2011,
    luminance_Fairchild2010,
    luminance_Fairchild2011,
)
from colour.hints import ArrayLike, Literal, NDArrayFloat
from colour.models.ipt import (
    MATRIX_IPT_IPT_TO_LMS_P,
    MATRIX_IPT_LMS_P_TO_IPT,
    MATRIX_IPT_LMS_TO_XYZ,
    MATRIX_IPT_XYZ_TO_LMS,
)
from colour.utilities import (
    as_float_array,
    domain_range_scale,
    from_range_1,
    from_range_100,
    to_domain_1,
    to_domain_100,
    validate_method,
)
from colour.utilities.documentation import (
    DocstringTuple,
    is_documentation_building,
)

__author__ = "Colour Developers"
__copyright__ = "Copyright 2013 Colour Developers"
__license__ = "BSD-3-Clause - https://opensource.org/licenses/BSD-3-Clause"
__maintainer__ = "Colour Developers"
__email__ = "colour-developers@colour-science.org"
__status__ = "Production"

__all__ = [
    "HDR_IPT_METHODS",
    "exponent_hdr_IPT",
    "XYZ_to_hdr_IPT",
    "hdr_IPT_to_XYZ",
]

HDR_IPT_METHODS: tuple = ("Fairchild 2010", "Fairchild 2011")
if is_documentation_building():  # pragma: no cover
    HDR_IPT_METHODS = DocstringTuple(HDR_IPT_METHODS)
    HDR_IPT_METHODS.__doc__ = """
Supported *hdr-IPT* colourspace computation methods.

References
----------
:cite:`Fairchild2010`, :cite:`Fairchild2011`
"""


def exponent_hdr_IPT(
    Y_s: ArrayLike,
    Y_abs: ArrayLike,
    method: (Literal["Fairchild 2011", "Fairchild 2010"] | str) = "Fairchild 2011",
) -> NDArrayFloat:
    """
    Compute *hdr-IPT* colourspace *Lightness* :math:`\\epsilon` exponent using
    *Fairchild and Wyble (2010)* or *Fairchild and Chen (2011)* method.

    Parameters
    ----------
    Y_s
        Relative luminance :math:`Y_s` of the surround.
    Y_abs
        Absolute luminance :math:`Y_{abs}` of the scene diffuse white in
        :math:`cd/m^2`.
    method
        Computation method.

    Returns
    -------
    :class:`numpy.ndarray`
        *hdr-IPT* colourspace *Lightness* :math:`\\epsilon` exponent.

    Notes
    -----
    +------------+-----------------------+---------------+
    | **Domain** | **Scale - Reference** | **Scale - 1** |
    +============+=======================+===============+
    | ``Y_s``    | [0, 1]                | [0, 1]        |
    +------------+-----------------------+---------------+

    Examples
    --------
    >>> exponent_hdr_IPT(0.2, 100)  # doctest: +ELLIPSIS
    0.4820209...
    >>> exponent_hdr_IPT(0.2, 100, method="Fairchild 2010")
    ... # doctest: +ELLIPSIS
    1.6891383...
    """

    Y_s = to_domain_1(Y_s)
    Y_abs = as_float_array(Y_abs)
    method = validate_method(method, HDR_IPT_METHODS)

    epsilon = 1.38 if method == "fairchild 2010" else 0.59

    lf = np.log(318) / np.log(Y_abs)
    sf = 1.25 - 0.25 * (Y_s / 0.184)
    if method == "fairchild 2010":
        epsilon *= sf * lf
    else:
        epsilon /= sf * lf

    return epsilon


[docs] def XYZ_to_hdr_IPT( XYZ: ArrayLike, Y_s: ArrayLike = 0.2, Y_abs: ArrayLike = 100, method: (Literal["Fairchild 2011", "Fairchild 2010"] | str) = "Fairchild 2011", ) -> NDArrayFloat: """ Convert from *CIE XYZ* tristimulus values to *hdr-IPT* colourspace. Parameters ---------- XYZ *CIE XYZ* tristimulus values. Y_s Relative luminance :math:`Y_s` of the surround. Y_abs Absolute luminance :math:`Y_{abs}` of the scene diffuse white in :math:`cd/m^2`. method Computation method. Returns ------- :class:`numpy.ndarray` *hdr-IPT* colourspace array. Notes ----- +-------------+-------------------------+---------------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +=============+=========================+=====================+ | ``XYZ`` | [0, 1] | [0, 1] | +-------------+-------------------------+---------------------+ | ``Y_s`` | [0, 1] | [0, 1] | +-------------+-------------------------+---------------------+ +-------------+-------------------------+---------------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +=============+=========================+=====================+ | ``IPT_hdr`` | ``I_hdr`` : [0, 100] | ``I_hdr`` : [0, 1] | | | | | | | ``P_hdr`` : [-100, 100] | ``P_hdr`` : [-1, 1] | | | | | | | ``T_hdr`` : [-100, 100] | ``T_hdr`` : [-1, 1] | +-------------+-------------------------+---------------------+ - Input *CIE XYZ* tristimulus values must be adapted to *CIE Standard Illuminant D Series* *D65*. References ---------- :cite:`Fairchild2010`, :cite:`Fairchild2011` Examples -------- >>> XYZ = np.array([0.20654008, 0.12197225, 0.05136952]) >>> XYZ_to_hdr_IPT(XYZ) # doctest: +ELLIPSIS array([ 48.3937634..., 42.4499020..., 22.0195403...]) >>> XYZ_to_hdr_IPT(XYZ, method="Fairchild 2010") # doctest: +ELLIPSIS array([ 30.0287314..., 83.9384506..., 34.9028738...]) """ XYZ = to_domain_1(XYZ) method = validate_method(method, HDR_IPT_METHODS) if method == "fairchild 2010": lightness_callable = lightness_Fairchild2010 else: lightness_callable = lightness_Fairchild2011 e = exponent_hdr_IPT(Y_s, Y_abs, method)[..., None] LMS = vector_dot(MATRIX_IPT_XYZ_TO_LMS, XYZ) # Domain and range scaling has already been handled. with domain_range_scale("ignore"): LMS_prime = np.sign(LMS) * np.abs(lightness_callable(LMS, e)) IPT_hdr = vector_dot(MATRIX_IPT_LMS_P_TO_IPT, LMS_prime) return from_range_100(IPT_hdr)
[docs] def hdr_IPT_to_XYZ( IPT_hdr: ArrayLike, Y_s: ArrayLike = 0.2, Y_abs: ArrayLike = 100, method: (Literal["Fairchild 2011", "Fairchild 2010"] | str) = "Fairchild 2011", ) -> NDArrayFloat: """ Convert from *hdr-IPT* colourspace to *CIE XYZ* tristimulus values. Parameters ---------- IPT_hdr *hdr-IPT* colourspace array. Y_s Relative luminance :math:`Y_s` of the surround. Y_abs Absolute luminance :math:`Y_{abs}` of the scene diffuse white in :math:`cd/m^2`. method Computation method. Returns ------- :class:`numpy.ndarray` *CIE XYZ* tristimulus values. Notes ----- +-------------+-------------------------+---------------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +=============+=========================+=====================+ | ``IPT_hdr`` | ``I_hdr`` : [0, 100] | ``I_hdr`` : [0, 1] | | | | | | | ``P_hdr`` : [-100, 100] | ``P_hdr`` : [-1, 1] | | | | | | | ``T_hdr`` : [-100, 100] | ``T_hdr`` : [-1, 1] | +-------------+-------------------------+---------------------+ | ``Y_s`` | [0, 1] | [0, 1] | +-------------+-------------------------+---------------------+ +-------------+-------------------------+---------------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +=============+=========================+=====================+ | ``XYZ`` | [0, 1] | [0, 1] | +-------------+-------------------------+---------------------+ References ---------- :cite:`Fairchild2010`, :cite:`Fairchild2011` Examples -------- >>> IPT_hdr = np.array([48.39376346, 42.44990202, 22.01954033]) >>> hdr_IPT_to_XYZ(IPT_hdr) # doctest: +ELLIPSIS array([ 0.2065400..., 0.1219722..., 0.0513695...]) >>> IPT_hdr = np.array([30.02873147, 83.93845061, 34.90287382]) >>> hdr_IPT_to_XYZ(IPT_hdr, method="Fairchild 2010") ... # doctest: +ELLIPSIS array([ 0.2065400..., 0.1219722..., 0.0513695...]) """ IPT_hdr = to_domain_100(IPT_hdr) method = validate_method(method, HDR_IPT_METHODS) if method == "fairchild 2010": luminance_callable = luminance_Fairchild2010 else: luminance_callable = luminance_Fairchild2011 e = exponent_hdr_IPT(Y_s, Y_abs, method)[..., None] LMS = vector_dot(MATRIX_IPT_IPT_TO_LMS_P, IPT_hdr) # Domain and range scaling has already be handled. with domain_range_scale("ignore"): LMS_prime = np.sign(LMS) * np.abs(luminance_callable(LMS, e)) XYZ = vector_dot(MATRIX_IPT_LMS_TO_XYZ, LMS_prime) return from_range_1(XYZ)