""" CAM16 Colour Appearance Model ============================= Define the *CAM16* colour appearance model for predicting perceptual colour attributes under varying viewing conditions. - :class:`colour.appearance.InductionFactors_CAM16` - :attr:`colour.VIEWING_CONDITIONS_CAM16` - :class:`colour.CAM_Specification_CAM16` - :func:`colour.XYZ_to_CAM16` - :func:`colour.CAM16_to_XYZ` References ---------- - :cite:`Li2017` : Li, C., Li, Z., Wang, Z., Xu, Y., Luo, M. R., Cui, G., Melgosa, M., Brill, M. H., & Pointer, M. (2017). Comprehensive color solutions: CAM16, CAT16, and CAM16-UCS. Color Research & Application, 42(6), 703-718. doi:10.1002/col.22131 """ from __future__ import annotations from dataclasses import astuple, dataclass, field import numpy as np from colour.adaptation import CAT_CAT16 from colour.algebra import spow, vecmul from colour.appearance.ciecam02 import ( VIEWING_CONDITIONS_CIECAM02, InductionFactors_CIECAM02, P, achromatic_response_forward, achromatic_response_inverse, brightness_correlate, chroma_correlate, colourfulness_correlate, degree_of_adaptation, eccentricity_factor, hue_angle, hue_quadrature, lightness_correlate, matrix_post_adaptation_non_linear_response_compression, opponent_colour_dimensions_forward, opponent_colour_dimensions_inverse, post_adaptation_non_linear_response_compression_forward, post_adaptation_non_linear_response_compression_inverse, saturation_correlate, temporary_magnitude_quantity_inverse, viewing_conditions_dependent_parameters, ) from colour.hints import ( # noqa: TC001 Annotated, ArrayLike, Domain100, NDArrayFloat, Range100, ) from colour.utilities import ( CanonicalMapping, MixinDataclassArithmetic, MixinDataclassIterable, as_float, as_float_array, from_range_100, from_range_degrees, has_only_nan, ones, to_domain_100, to_domain_degrees, tsplit, ) __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__ = [ "MATRIX_16", "MATRIX_INVERSE_16", "InductionFactors_CAM16", "VIEWING_CONDITIONS_CAM16", "CAM_Specification_CAM16", "XYZ_to_CAM16", "CAM16_to_XYZ", ] MATRIX_16: NDArrayFloat = CAT_CAT16 """Adaptation matrix :math:`M_{16}`.""" MATRIX_INVERSE_16: NDArrayFloat = np.linalg.inv(MATRIX_16) """Inverse adaptation matrix :math:`M^{-1}_{16}`.""" @dataclass(frozen=True) class InductionFactors_CAM16(MixinDataclassIterable): """ Define the *CAM16* colour appearance model induction factors. Parameters ---------- F Maximum degree of adaptation :math:`F`. c Exponential non-linearity :math:`c`. N_c Chromatic induction factor :math:`N_c`. Notes ----- - The *CAM16* colour appearance model induction factors are identical to the *CIECAM02* colour appearance model induction factors. References ---------- :cite:`Li2017` """ F: float c: float N_c: float VIEWING_CONDITIONS_CAM16: CanonicalMapping = CanonicalMapping( VIEWING_CONDITIONS_CIECAM02 ) VIEWING_CONDITIONS_CAM16.__doc__ = """ Define the reference *CAM16* colour appearance model viewing conditions. References ---------- :cite:`Li2017` """ @dataclass class CAM_Specification_CAM16(MixinDataclassArithmetic): """ Define the *CAM16* colour appearance model specification. Parameters ---------- J Correlate of *lightness* :math:`J`. C Correlate of *chroma* :math:`C`. h *Hue* angle :math:`h` in degrees. s Correlate of *saturation* :math:`s`. Q Correlate of *brightness* :math:`Q`. M Correlate of *colourfulness* :math:`M`. H *Hue* :math:`h` quadrature :math:`H`. HC *Hue* :math:`h` composition :math:`H^C`. References ---------- :cite:`Li2017` """ J: float | NDArrayFloat | None = field(default_factory=lambda: None) C: float | NDArrayFloat | None = field(default_factory=lambda: None) h: float | NDArrayFloat | None = field(default_factory=lambda: None) s: float | NDArrayFloat | None = field(default_factory=lambda: None) Q: float | NDArrayFloat | None = field(default_factory=lambda: None) M: float | NDArrayFloat | None = field(default_factory=lambda: None) H: float | NDArrayFloat | None = field(default_factory=lambda: None) HC: float | NDArrayFloat | None = field(default_factory=lambda: None) def XYZ_to_CAM16( XYZ: Domain100, XYZ_w: Domain100, L_A: ArrayLike, Y_b: ArrayLike, surround: ( InductionFactors_CIECAM02 | InductionFactors_CAM16 ) = VIEWING_CONDITIONS_CAM16["Average"], discount_illuminant: bool = False, compute_H: bool = True, ) -> Annotated[CAM_Specification_CAM16, (100, 100, 360, 100, 100, 100, 400)]: """ Compute the *CAM16* colour appearance model correlates from the specified *CIE XYZ* tristimulus values. Parameters ---------- XYZ *CIE XYZ* tristimulus values of test sample / stimulus. XYZ_w *CIE XYZ* tristimulus values of reference white. L_A Adapting field *luminance* :math:`L_A` in :math:`cd/m^2`, (often taken to be 20% of the luminance of a white object in the scene). Y_b Luminous factor of background :math:`Y_b` such as :math:`Y_b = 100 \\times L_b / L_w` where :math:`L_w` is the luminance of the light source and :math:`L_b` is the luminance of the background. For viewing images, :math:`Y_b` can be the average :math:`Y` value for the pixels in the entire image, or frequently, a :math:`Y` value of 20, approximating an :math:`L^*` of 50 is used. surround Surround viewing conditions induction factors. discount_illuminant Truth value indicating if the illuminant should be discounted. compute_H Whether to compute *Hue* :math:`h` quadrature :math:`H`. :math:`H` is rarely used, and expensive to compute. Returns ------- :class:`colour.CAM_Specification_CAM16` *CAM16* colour appearance model specification. Notes ----- +---------------------+-----------------------+---------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +=====================+=======================+===============+ | ``XYZ`` | 100 | 1 | +---------------------+-----------------------+---------------+ | ``XYZ_w`` | 100 | 1 | +---------------------+-----------------------+---------------+ +---------------------+-----------------------+---------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +=====================+=======================+===============+ | ``specification.J`` | 100 | 1 | +---------------------+-----------------------+---------------+ | ``specification.C`` | 100 | 1 | +---------------------+-----------------------+---------------+ | ``specification.h`` | 360 | 1 | +---------------------+-----------------------+---------------+ | ``specification.s`` | 100 | 1 | +---------------------+-----------------------+---------------+ | ``specification.Q`` | 100 | 1 | +---------------------+-----------------------+---------------+ | ``specification.M`` | 100 | 1 | +---------------------+-----------------------+---------------+ | ``specification.H`` | 400 | 1 | +---------------------+-----------------------+---------------+ References ---------- :cite:`Li2017` Examples -------- >>> XYZ = np.array([19.01, 20.00, 21.78]) >>> XYZ_w = np.array([95.05, 100.00, 108.88]) >>> L_A = 318.31 >>> Y_b = 20.0 >>> surround = VIEWING_CONDITIONS_CAM16["Average"] >>> XYZ_to_CAM16(XYZ, XYZ_w, L_A, Y_b, surround) # doctest: +ELLIPSIS CAM_Specification_CAM16(J=41.7312079..., C=0.1033557..., \ h=217.0679597..., s=2.3450150..., Q=195.3717089..., M=0.1074367..., \ H=275.5949861..., HC=None) """ XYZ = to_domain_100(XYZ) XYZ_w = to_domain_100(XYZ_w) _X_w, Y_w, _Z_w = tsplit(XYZ_w) L_A = as_float_array(L_A) Y_b = as_float_array(Y_b) # Step 0 # Converting *CIE XYZ* tristimulus values to sharpened *RGB* values. RGB_w = vecmul(MATRIX_16, XYZ_w) # Computing degree of adaptation :math:`D`. D = ( np.clip(degree_of_adaptation(surround.F, L_A), 0, 1) if not discount_illuminant else ones(L_A.shape) ) n, F_L, N_bb, N_cb, z = viewing_conditions_dependent_parameters(Y_b, Y_w, L_A) D_RGB = D[..., None] * Y_w[..., None] / RGB_w + 1 - D[..., None] RGB_wc = D_RGB * RGB_w # Applying forward post-adaptation non-linear response compression. RGB_aw = post_adaptation_non_linear_response_compression_forward(RGB_wc, F_L) # Computing achromatic responses for the whitepoint. A_w = achromatic_response_forward(RGB_aw, N_bb) # Step 1 # Converting *CIE XYZ* tristimulus values to sharpened *RGB* values. RGB = vecmul(MATRIX_16, XYZ) # Step 2 RGB_c = D_RGB * RGB # Step 3 # Applying forward post-adaptation non-linear response compression. RGB_a = post_adaptation_non_linear_response_compression_forward(RGB_c, F_L) # Step 4 # Converting to preliminary cartesian coordinates. a, b = tsplit(opponent_colour_dimensions_forward(RGB_a)) # Computing the *hue* angle :math:`h`. h = hue_angle(a, b) # Step 5 # Computing eccentricity factor *e_t*. e_t = eccentricity_factor(h) # Computing hue :math:`h` quadrature :math:`H`. H = hue_quadrature(h) if compute_H else np.full(h.shape, np.nan) # TODO: Compute hue composition. # Step 6 # Computing achromatic responses for the stimulus. A = achromatic_response_forward(RGB_a, N_bb) # Step 7 # Computing the correlate of *Lightness* :math:`J`. J = lightness_correlate(A, A_w, surround.c, z) # Step 8 # Computing the correlate of *brightness* :math:`Q`. Q = brightness_correlate(surround.c, J, A_w, F_L) # Step 9 # Computing the correlate of *chroma* :math:`C`. C = chroma_correlate(J, n, surround.N_c, N_cb, e_t, a, b, RGB_a) # Computing the correlate of *colourfulness* :math:`M`. M = colourfulness_correlate(C, F_L) # Computing the correlate of *saturation* :math:`s`. s = saturation_correlate(M, Q) return CAM_Specification_CAM16( J=as_float(from_range_100(J)), C=as_float(from_range_100(C)), h=as_float(from_range_degrees(h)), s=as_float(from_range_100(s)), Q=as_float(from_range_100(Q)), M=as_float(from_range_100(M)), H=as_float(from_range_degrees(H, 400)), HC=None, ) def CAM16_to_XYZ( specification: Annotated[ CAM_Specification_CAM16, (100, 100, 360, 100, 100, 100, 400) ], XYZ_w: Domain100, L_A: ArrayLike, Y_b: ArrayLike, surround: ( InductionFactors_CIECAM02 | InductionFactors_CAM16 ) = VIEWING_CONDITIONS_CAM16["Average"], discount_illuminant: bool = False, ) -> Range100: """ Convert the *CAM16* colour appearance model specification to *CIE XYZ* tristimulus values. Parameters ---------- specification *CAM16* colour appearance model specification. Correlate of *lightness* :math:`J`, correlate of *chroma* :math:`C` or correlate of *colourfulness* :math:`M` and *hue* angle :math:`h` in degrees must be specified, e.g., :math:`JCh` or :math:`JMh`. XYZ_w *CIE XYZ* tristimulus values of reference white. L_A Adapting field *luminance* :math:`L_A` in :math:`cd/m^2`, (often taken to be 20% of the luminance of a white object in the scene). Y_b Luminous factor of background :math:`Y_b` such as :math:`Y_b = 100 \\times L_b / L_w` where :math:`L_w` is the luminance of the light source and :math:`L_b` is the luminance of the background. For viewing images, :math:`Y_b` can be the average :math:`Y` value for the pixels in the entire image, or frequently, a :math:`Y` value of 20, approximating an :math:`L^*` of 50 is used. surround Surround viewing conditions induction factors. discount_illuminant Truth value indicating if the illuminant should be discounted. Returns ------- :class:`numpy.ndarray` *CIE XYZ* tristimulus values. Raises ------ ValueError If neither :math:`C` nor :math:`M` correlates have been defined in the ``specification`` argument. Notes ----- +---------------------+-----------------------+---------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +=====================+=======================+===============+ | ``specification.J`` | 100 | 1 | +---------------------+-----------------------+---------------+ | ``specification.C`` | 100 | 1 | +---------------------+-----------------------+---------------+ | ``specification.h`` | 360 | 1 | +---------------------+-----------------------+---------------+ | ``specification.s`` | 100 | 1 | +---------------------+-----------------------+---------------+ | ``specification.Q`` | 100 | 1 | +---------------------+-----------------------+---------------+ | ``specification.M`` | 100 | 1 | +---------------------+-----------------------+---------------+ | ``specification.H`` | 360 | 1 | +---------------------+-----------------------+---------------+ | ``XYZ_w`` | 100 | 1 | +---------------------+-----------------------+---------------+ +---------------------+-----------------------+---------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +=====================+=======================+===============+ | ``XYZ`` | 100 | 1 | +---------------------+-----------------------+---------------+ References ---------- :cite:`Li2017` Examples -------- >>> specification = CAM_Specification_CAM16( ... J=41.731207905126638, C=0.103355738709070, h=217.067959767393010 ... ) >>> XYZ_w = np.array([95.05, 100.00, 108.88]) >>> L_A = 318.31 >>> Y_b = 20.0 >>> CAM16_to_XYZ(specification, XYZ_w, L_A, Y_b) # doctest: +ELLIPSIS array([ 19.01..., 20... , 21.78...]) """ J, C, h, _s, _Q, M, _H, _HC = astuple(specification) J = to_domain_100(J) C = to_domain_100(C) h = to_domain_degrees(h) M = to_domain_100(M) L_A = as_float_array(L_A) XYZ_w = to_domain_100(XYZ_w) _X_w, Y_w, _Z_w = tsplit(XYZ_w) # Step 0 # Converting *CIE XYZ* tristimulus values to sharpened *RGB* values. RGB_w = vecmul(MATRIX_16, XYZ_w) # Computing degree of adaptation :math:`D`. D = ( np.clip(degree_of_adaptation(surround.F, L_A), 0, 1) if not discount_illuminant else ones(L_A.shape) ) n, F_L, N_bb, N_cb, z = viewing_conditions_dependent_parameters(Y_b, Y_w, L_A) D_RGB = D[..., None] * Y_w[..., None] / RGB_w + 1 - D[..., None] RGB_wc = D_RGB * RGB_w # Applying forward post-adaptation non-linear response compression. RGB_aw = post_adaptation_non_linear_response_compression_forward(RGB_wc, F_L) # Computing achromatic responses for the whitepoint. A_w = achromatic_response_forward(RGB_aw, N_bb) # Step 1 if has_only_nan(C) and not has_only_nan(M): C = M / spow(F_L, 0.25) elif has_only_nan(C): error = ( 'Either "C" or "M" correlate must be defined in ' 'the "CAM_Specification_CAM16" argument!' ) raise ValueError(error) # Step 2 # Computing temporary magnitude quantity :math:`t`. t = temporary_magnitude_quantity_inverse(C, J, n) # Computing eccentricity factor *e_t*. e_t = eccentricity_factor(h) # Computing achromatic response :math:`A` for the stimulus. A = achromatic_response_inverse(A_w, J, surround.c, z) # Computing *P_1* to *P_3*. P_n = P(surround.N_c, N_cb, e_t, t, A, N_bb) _P_1, P_2, _P_3 = tsplit(P_n) # Step 3 # Computing opponent colour dimensions :math:`a` and :math:`b`. ab = opponent_colour_dimensions_inverse(P_n, h) a, b = tsplit(ab) * np.where(t == 0, 0, 1) # Step 4 # Applying post-adaptation non-linear response compression matrix. RGB_a = matrix_post_adaptation_non_linear_response_compression(P_2, a, b) # Step 5 # Applying inverse post-adaptation non-linear response compression. RGB_c = post_adaptation_non_linear_response_compression_inverse(RGB_a, F_L) # Step 6 RGB = RGB_c / D_RGB # Step 7 XYZ = vecmul(MATRIX_INVERSE_16, RGB) return from_range_100(XYZ)