[BUG]: XYZ_to_xyY giving 0

[gul916]

Description

Hi,
When converting sRGB black value [0, 0, 0] to xyY color model, we obtain [0, 0, 0]. It is rather expected to obtain the D65 white point with Y=0, [0.3127, 0.329, 0]. The opposite operation from black point in xyY to XYZ is working.
Thanks.

Code for Reproduction

import colour
import numpy as np

illum_ccs = colour.CCS_ILLUMINANTS['cie_2_1931']['D65']

XYZ = colour.RGB_to_XYZ([0, 0, 0], 'sRGB', illum_ccs, 'CAT16', True)
xyY = colour.XYZ_to_xyY(XYZ)    # [0., 0., 0.]

xyY_2 = np.append(illum_ccs, 0) # [0.3127, 0.329, 0.]
XYZ_2 = colour.xyY_XYZ(xyY_2)   # [0., 0., 0.]

Exception Message

No response

Environment Information

===============================================================================
*                                                                             *
*   Interpreter :                                                             *
*       python : 3.12.4 | packaged by Anaconda, Inc. | (main, Jun 18 2024,    *
*   15:03:56) [MSC v.1929 64 bit (AMD64)]                                     *
*                                                                             *
*   colour-science.org :                                                      *
*       colour : 0.4.6                                                        *
*                                                                             *
*   Runtime :                                                                 *
*       imageio : 2.36.0                                                      *
*       matplotlib : 3.9.2                                                    *
*       networkx : 3.3                                                        *
*       numpy : 1.26.4                                                        *
*       pandas : 2.2.2                                                        *
*       scipy : 1.13.1                                                        *
*       trimesh : 4.4.9                                                       *
*                                                                             *
===============================================================================

[KelSolaar]

Hello @gul916,

We actually removed this for consistency with other chromaticity coordinates transformations, #1153. We now recommend that users deal with this case on their end by either adding a small epsilon to their values or after the conversion: https://github.com/colour-science/colour-visuals/blob/085585911924072231a6f833365a8f56716a1ea8/colour_visuals/rgb_colourspace.py#L376

Cheers,

Thomas

[gul916]

Thank you Thomas for the explanation, I understand. I added an additional line to take this case into account.
Cheers,