Comments (6)
Those are unfortunately expected and related to #1227 as the model fitting does not match exactly yield the input whitepoint which can be verified by converting Lightness J=100 to CIE XYZ:
import colour
print(
colour.xy_to_XYZ(
colour.CCS_ILLUMINANTS["CIE 1931 2 Degree Standard Observer"]["D65"]
)
)
XYZ = colour.sRGB_to_XYZ([1, 1, 1])
print(XYZ)
XYZ = colour.CIECAM02_to_XYZ(
colour.CAM_Specification_CIECAM02(100, 0, 0),
**colour.appearance.CAM_KWARGS_CIECAM02_sRGB
)
print(XYZ / XYZ[1])
XYZ = colour.CIECAM16_to_XYZ(
colour.CAM_Specification_CIECAM16(100, 0, 0),
**colour.appearance.CAM_KWARGS_CIECAM02_sRGB
)
print(XYZ / XYZ[1])
[ 0.95045593 1. 1.08905775]
[ 0.9505 1. 1.089 ]
[ 0.95854868 1. 1.07335032]
[ 0.95857463 1. 1.07307191]
Cheers,
Thomas
from colour.
I don't quite understand. Are you saying this is a problem inherent in the model specification of CIECAM16? or just this specific package's implementation?
from colour.
The model itself.
from colour.
It's actually a pretty big difference, dE2000 > 2
import colour
CAM_white = colour.convert([1,0,0], 'CIECAM16 JMh', 'CIE XYZ')
sRGB_white = colour.convert([1,1,1], 'sRGB', 'CIE XYZ')
colour.difference.delta_E_CIE2000(
colour.convert(CAM_white, 'CIE XYZ', 'CIE Lab')*100,
colour.convert(sRGB_white, 'CIE XYZ', 'CIE Lab')*100,
)
2.2151311708854311
And it happens no matter the reference white point.
D50 = colour.TVS_ILLUMINANTS['CIE 1931 2 Degree Standard Observer']['D50']/100
CAM_white = colour.convert([1,0,0], 'CIECAM16 JMh', 'CIE XYZ', XYZ_w=D50)
colour.difference.delta_E_CIE2000(
colour.convert(D50, 'CIE XYZ', 'CIE Lab')*100,
colour.convert(CAM_white, 'CIE XYZ', 'CIE Lab')*100
)
1.6821909479182446
I'm pretty unnerved to be honest. Isn't the model supposed to use the given white point as the reference? How could it be so far off?
So what's the correct way of dealing with this if we actually want M=0 to correspond to the given white point? When I use discount_illuminant=True
, the value is much closer.
colour.convert([1,0,0], 'CIECAM16 JMh', 'sRGB', discount_illuminant=True)
array([ 0.99993111, 1.00004358, 1.00003272])
But is that the correct way to do it? I'm not sure what the interpretation is here.
from colour.
from colour.
Related Issues (20)
- When will the next version up come?
- [FEATURE]: Implement "Modifications of the Robertson Method for Calculating Correlated Color Temperature to Improve Accuracy and Speed" HOT 1
- How to use recent `ColourChecker` related code? HOT 1
- [FEATURE]: Implement support for global to set the `colour.plotting.render` et al. defaults.
- [FEATURE]: Implement support for *Apple Log Profile*. HOT 2
- [BUG]: Unable to use the `colour.RGB_to_XYZ` definition. HOT 3
- [BUG]: *nan* are generated by `colour.difference.delta_E_CIE1994` definition. HOT 3
- How to convert Rec.709 color space to Sony S-Gammut color space? HOT 2
- [BUG]: Write LUT without extension HOT 3
- [BUG]: Exception raised in `colour.plotting.plot_RGB_scatter` definition. HOT 4
- [FEATURE]: Implement support for "Weighted Geometric Mean (WGM) method: A new chromatic adaptation model".
- [FEATURE]: Implement support for concurrent installation with `vaab/colour` Pypi package. HOT 7
- [BUG]: Numerical precision issues with CIECAM02 and CIECAM16 for L_A = 0 and Y_b = 0 HOT 18
- [DOCUMENTATION]: Typo in spectral upsampling docs HOT 1
- [BUG]: Planckian locus CCT curves come out of plot HOT 2
- [FEATURE]: Implement support for *sCAM* colour appearance model.
- [ENHANCEMENT] ARRI White paper now gives matrices to 18 decimal places. HOT 1
- [FEATURE]: Implement smooth D and ID illuminants in CIE 204:2013 "Methods for Re-defining CIE D Illuminants" HOT 3
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from colour.