Source code for colour.models.cie_uvw

# -*- coding: utf-8 -*-
"""
CIE 1964 U*V*W* Colourspace
===========================

Defines the *CIE 1964 U\\*V\\*W\\** colourspace transformations:

-   :func:`colour.XYZ_to_UVW`
-   :func:`colour.UVW_to_XYZ`

References
----------
-   :cite:`Wikipedia2008a` : Wikipedia. (2008). CIE 1964 color space.
    Retrieved June 10, 2014, from
    http://en.wikipedia.org/wiki/CIE_1964_color_space
"""

from __future__ import division, unicode_literals

from colour.algebra import spow
from colour.colorimetry import ILLUMINANTS
from colour.models import (UCS_to_uv, UCS_uv_to_xy, XYZ_to_UCS, XYZ_to_xyY,
                           xy_to_UCS_uv, xyY_to_XYZ, xyY_to_xy)
from colour.utilities import from_range_100, to_domain_100, tsplit, tstack

__author__ = 'Colour Developers'
__copyright__ = 'Copyright (C) 2013-2020 - Colour Developers'
__license__ = 'New BSD License - https://opensource.org/licenses/BSD-3-Clause'
__maintainer__ = 'Colour Developers'
__email__ = 'colour-developers@colour-science.org'
__status__ = 'Production'

__all__ = ['XYZ_to_UVW', 'UVW_to_XYZ']


[docs]def XYZ_to_UVW( XYZ, illuminant=ILLUMINANTS['CIE 1931 2 Degree Standard Observer']['D65']): """ Converts from *CIE XYZ* tristimulus values to *CIE 1964 U\\*V\\*W\\** colourspace. Parameters ---------- XYZ : array_like *CIE XYZ* tristimulus values. illuminant : array_like, optional Reference *illuminant* *CIE xy* chromaticity coordinates or *CIE xyY* colourspace array. Returns ------- ndarray *CIE 1964 U\\*V\\*W\\** colourspace array. Warning ------- The input domain and output range of that definition are non standard! Notes ----- +----------------+-----------------------+-----------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +================+=======================+=================+ | ``XYZ`` | [0, 1] | [0, 1] | +----------------+-----------------------+-----------------+ | ``illuminant`` | [0, 1] | [0, 1] | +----------------+-----------------------+-----------------+ +----------------+-----------------------+-----------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +================+=======================+=================+ | ``UVW`` | ``U`` : [-100, 100] | ``U`` : [-1, 1] | | | | | | | ``V`` : [-100, 100] | ``V`` : [-1, 1] | | | | | | | ``W`` : [0, 100] | ``W`` : [0, 1] | +----------------+-----------------------+-----------------+ References ---------- :cite:`Wikipedia2008a` Examples -------- >>> import numpy as np >>> XYZ = np.array([0.20654008, 0.12197225, 0.05136952]) * 100 >>> XYZ_to_UVW(XYZ) # doctest: +ELLIPSIS array([ 94.5503572..., 11.5553652..., 40.5475740...]) """ XYZ = to_domain_100(XYZ) xy = xyY_to_xy(illuminant) xyY = XYZ_to_xyY(XYZ, xy) _x, _y, Y = tsplit(xyY) u, v = tsplit(UCS_to_uv(XYZ_to_UCS(XYZ))) u_0, v_0 = tsplit(xy_to_UCS_uv(xy)) W = 25 * spow(Y, 1 / 3) - 17 U = 13 * W * (u - u_0) V = 13 * W * (v - v_0) UVW = tstack([U, V, W]) return from_range_100(UVW)
[docs]def UVW_to_XYZ( UVW, illuminant=ILLUMINANTS['CIE 1931 2 Degree Standard Observer']['D65']): """ Converts *CIE 1964 U\\*V\\*W\\** colourspace to *CIE XYZ* tristimulus values. Parameters ---------- UVW : array_like *CIE 1964 U\\*V\\*W\\** colourspace array. illuminant : array_like, optional Reference *illuminant* *CIE xy* chromaticity coordinates or *CIE xyY* colourspace array. Returns ------- ndarray *CIE XYZ* tristimulus values. Warning ------- The input domain and output range of that definition are non standard! Notes ----- +----------------+-----------------------+-----------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +================+=======================+=================+ | ``UVW`` | ``U`` : [-100, 100] | ``U`` : [-1, 1] | | | | | | | ``V`` : [-100, 100] | ``V`` : [-1, 1] | | | | | | | ``W`` : [0, 100] | ``W`` : [0, 1] | +----------------+-----------------------+-----------------+ | ``illuminant`` | [0, 1] | [0, 1] | +----------------+-----------------------+-----------------+ +----------------+-----------------------+-----------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +================+=======================+=================+ | ``XYZ`` | [0, 1] | [0, 1] | +----------------+-----------------------+-----------------+ References ---------- :cite:`Wikipedia2008a` Examples -------- >>> import numpy as np >>> UVW = np.array([94.55035725, 11.55536523, 40.54757405]) >>> UVW_to_XYZ(UVW) array([ 20.654008, 12.197225, 5.136952]) """ U, V, W = tsplit(to_domain_100(UVW)) u_0, v_0 = tsplit(xy_to_UCS_uv(xyY_to_xy(illuminant))) Y = ((W + 17) / 25) ** 3 u = U / (13 * W) + u_0 v = V / (13 * W) + v_0 x, y = tsplit(UCS_uv_to_xy(tstack([u, v]))) XYZ = xyY_to_XYZ(tstack([x, y, Y])) return from_range_100(XYZ)