def deltaE_ciede94(lab1, lab2, kH=1, kC=1, kL=1, k1=0.045, k2=0.015):
"""Color difference according to CIEDE 94 standard
Accommodates perceptual non-uniformities through the use of application
specific scale factors (`kH`, `kC`, `kL`, `k1`, and `k2`).
Parameters
----------
lab1 : array_like
reference color (Lab colorspace)
lab2 : array_like
comparison color (Lab colorspace)
kH : float, optional
Hue scale
kC : float, optional
Chroma scale
kL : float, optional
Lightness scale
k1 : float, optional
first scale parameter
k2 : float, optional
second scale parameter
Returns
-------
dE : array_like
color difference between `lab1` and `lab2`
Notes
-----
deltaE_ciede94 is not symmetric with respect to lab1 and lab2. CIEDE94
defines the scales for the lightness, hue, and chroma in terms of the first
color. Consequently, the first color should be regarded as the "reference"
color.
`kL`, `k1`, `k2` depend on the application and default to the values
suggested for graphic arts
========== ============== ==========
Parameter Graphic Arts Textiles
========== ============== ==========
`kL` 1.000 2.000
`k1` 0.045 0.048
`k2` 0.015 0.014
========== ============== ==========
References
----------
.. [1] http://en.wikipedia.org/wiki/Color_difference
.. [2] http://www.brucelindbloom.com/index.html?Eqn_DeltaE_CIE94.html
"""
L1, C1 = np.rollaxis(lab2lch(lab1), -1)[:2]
L2, C2 = np.rollaxis(lab2lch(lab2), -1)[:2]
dL = L1 - L2
dC = C1 - C2
dH2 = get_dH2(lab1, lab2)
SL = 1
SC = 1 + k1 * C1
SH = 1 + k2 * C1
dE2 = (dL / (kL * SL))**2
dE2 += (dC / (kC * SC))**2
dE2 += dH2 / (kH * SH)**2
return np.sqrt(dE2)
def deltaE_ciede94(lab1, lab2, kH=1, kC=1, kL=1, k1=0.045, k2=0.015):
"""Color difference according to CIEDE 94 standard
Accommodates perceptual non-uniformities through the use of application
specific scale factors (`kH`, `kC`, `kL`, `k1`, and `k2`).
Parameters
----------
lab1 : array_like
reference color (Lab colorspace)
lab2 : array_like
comparison color (Lab colorspace)
kH : float, optional
Hue scale
kC : float, optional
Chroma scale
kL : float, optional
Lightness scale
k1 : float, optional
first scale parameter
k2 : float, optional
second scale parameter
Returns
-------
dE : array_like
color difference between `lab1` and `lab2`
Notes
-----
deltaE_ciede94 is not symmetric with respect to lab1 and lab2. CIEDE94
defines the scales for the lightness, hue, and chroma in terms of the first
color. Consequently, the first color should be regarded as the "reference"
color.
`kL`, `k1`, `k2` depend on the application and default to the values
suggested for graphic arts
========== ============== ==========
Parameter Graphic Arts Textiles
========== ============== ==========
`kL` 1.000 2.000
`k1` 0.045 0.048
`k2` 0.015 0.014
========== ============== ==========
References
----------
.. [1] http://en.wikipedia.org/wiki/Color_difference
.. [2] http://www.brucelindbloom.com/index.html?Eqn_DeltaE_CIE94.html
"""
L1, C1 = np.rollaxis(lab2lch(lab1), -1)[:2]
L2, C2 = np.rollaxis(lab2lch(lab2), -1)[:2]
dL = L1 - L2
dC = C1 - C2
dH2 = get_dH2(lab1, lab2)
SL = 1
SC = 1 + k1 * C1
SH = 1 + k2 * C1
dE2 = (dL / (kL * SL)) ** 2
dE2 += (dC / (kC * SC)) ** 2
dE2 += dH2 / (kH * SH) ** 2
return np.sqrt(dE2)
def deltaE_cmc(lab1, lab2, kL=1, kC=1):
"""Color difference from the CMC l:c standard.
This color difference was developed by the Colour Measurement Committee
(CMC) of the Society of Dyers and Colourists (United Kingdom). It is
intended for use in the textile industry.
The scale factors `kL`, `kC` set the weight given to differences in
lightness and chroma relative to differences in hue. The usual values are
``kL=2``, ``kC=1`` for "acceptability" and ``kL=1``, ``kC=1`` for
"imperceptibility". Colors with ``dE > 1`` are "different" for the given
scale factors.
Parameters
----------
lab1 : array_like
reference color (Lab colorspace)
lab2 : array_like
comparison color (Lab colorspace)
Returns
-------
dE : array_like
distance between colors `lab1` and `lab2`
Notes
-----
deltaE_cmc the defines the scales for the lightness, hue, and chroma
in terms of the first color. Consequently
``deltaE_cmc(lab1, lab2) != deltaE_cmc(lab2, lab1)``
References
----------
.. [1] http://en.wikipedia.org/wiki/Color_difference
.. [2] http://www.brucelindbloom.com/index.html?Eqn_DeltaE_CIE94.html
.. [3] F. J. J. Clarke, R. McDonald, and B. Rigg, "Modification to the
JPC79 colour-difference formula," J. Soc. Dyers Colour. 100, 128-132
(1984).
"""
L1, C1, h1 = np.rollaxis(lab2lch(lab1), -1)[:3]
L2, C2, h2 = np.rollaxis(lab2lch(lab2), -1)[:3]
dC = C1 - C2
dL = L1 - L2
dH2 = get_dH2(lab1, lab2)
T = np.where(np.logical_and(np.rad2deg(h1) >= 164,
np.rad2deg(h1) <= 345),
0.56 + 0.2 * np.abs(np.cos(h1 + np.deg2rad(168))),
0.36 + 0.4 * np.abs(np.cos(h1 + np.deg2rad(35))))
c1_4 = C1**4
F = np.sqrt(c1_4 / (c1_4 + 1900))
SL = np.where(L1 < 16, 0.511, 0.040975 * L1 / (1. + 0.01765 * L1))
SC = 0.638 + 0.0638 * C1 / (1. + 0.0131 * C1)
SH = SC * (F * T + 1 - F)
dE2 = (dL / (kL * SL))**2
dE2 += (dC / (kC * SC))**2
dE2 += dH2 / (SH**2)
return np.sqrt(dE2)
def deltaE_cmc(lab1, lab2, kL=1, kC=1):
"""Color difference from the CMC l:c standard.
This color difference was developed by the Colour Measurement Committee
(CMC) of the Society of Dyers and Colourists (United Kingdom). It is
intended for use in the textile industry.
The scale factors `kL`, `kC` set the weight given to differences in
lightness and chroma relative to differences in hue. The usual values are
``kL=2``, ``kC=1`` for "acceptability" and ``kL=1``, ``kC=1`` for
"imperceptibility". Colors with ``dE > 1`` are "different" for the given
scale factors.
Parameters
----------
lab1 : array_like
reference color (Lab colorspace)
lab2 : array_like
comparison color (Lab colorspace)
Returns
-------
dE : array_like
distance between colors `lab1` and `lab2`
Notes
-----
deltaE_cmc the defines the scales for the lightness, hue, and chroma
in terms of the first color. Consequently
``deltaE_cmc(lab1, lab2) != deltaE_cmc(lab2, lab1)``
References
----------
.. [1] http://en.wikipedia.org/wiki/Color_difference
.. [2] http://www.brucelindbloom.com/index.html?Eqn_DeltaE_CIE94.html
.. [3] F. J. J. Clarke, R. McDonald, and B. Rigg, "Modification to the
JPC79 colour-difference formula," J. Soc. Dyers Colour. 100, 128-132
(1984).
"""
L1, C1, h1 = np.rollaxis(lab2lch(lab1), -1)[:3]
L2, C2, h2 = np.rollaxis(lab2lch(lab2), -1)[:3]
dC = C1 - C2
dL = L1 - L2
dH2 = get_dH2(lab1, lab2)
T = np.where(np.logical_and(np.rad2deg(h1) >= 164, np.rad2deg(h1) <= 345),
0.56 + 0.2 * np.abs(np.cos(h1 + np.deg2rad(168))),
0.36 + 0.4 * np.abs(np.cos(h1 + np.deg2rad(35)))
)
c1_4 = C1 ** 4
F = np.sqrt(c1_4 / (c1_4 + 1900))
SL = np.where(L1 < 16, 0.511, 0.040975 * L1 / (1. + 0.01765 * L1))
SC = 0.638 + 0.0638 * C1 / (1. + 0.0131 * C1)
SH = SC * (F * T + 1 - F)
dE2 = (dL / (kL * SL)) ** 2
dE2 += (dC / (kC * SC)) ** 2
dE2 += dH2 / (SH ** 2)
return np.sqrt(dE2)