[FEATURE]: Update of the colour.XYZ_to_RGB and colour.RGB_to_XYZ definition signatures. #1127
Description
Description
Introduction
What follows has been triggered by a discussion with Rod Bogart.
colour.XYZ_to_RGB
Let us consider the current signature of the colour.XYZ_to_RGB definition:
def XYZ_to_RGB(
XYZ: ArrayLike,
illuminant_XYZ: ArrayLike,
illuminant_RGB: ArrayLike,
matrix_XYZ_to_RGB: ArrayLike,
chromatic_adaptation_transform: Literal["Bianco 2010", "Bianco PC 2010", "Bradford", "CAT02 Brill 2008", "CAT02", "CAT16", "CMCCAT2000", "CMCCAT97", "Fairchild", "Sharp", "Von Kries", "XYZ Scaling"] | str | None = "CAT02",
cctf_encoding: Callable | None = None,
) -> NDArrayFloat:
...Doing the conversion without chromatic adaptation requires passing the following arguments:
illuminant_XYZilluminant_RGBchromatic_adaptation_transform
When ideally, only matrix_XYZ_to_RGB should be required. One would argue that for a conversion without chromatic adaptation one could simply do RGB = vector_dot(matrix_XYZ_to_RGB, XYZ)
colour.RGB_to_RGB
We also have the colour.RGB_to_RGB definition:
def RGB_to_RGB(
RGB: ArrayLike,
input_colourspace: RGB_Colourspace,
output_colourspace: RGB_Colourspace,
chromatic_adaptation_transform: Literal["Bianco 2010", "Bianco PC 2010", "Bradford", "CAT02 Brill 2008", "CAT02", "CAT16", "CMCCAT2000", "CMCCAT97", "Fairchild", "Sharp", "Von Kries", "XYZ Scaling"] | str | None = "CAT02",
apply_cctf_decoding: bool = False,
apply_cctf_encoding: bool = False,
**kwargs: Any,
) -> NDArrayFloat:
...Note how it takes directly a colour. RGB_Colourspace as argument and defines whether to use the decoding and encoding cctf.
Enhancement Proposal
Having to pass the 3 arguments when no CAT is desired is not a great design, Rod suggested having a colour.XYZ_to_RGB_no_CAT definition. I would like to see if we can modify the existing definition.
Something as follows seems better and more inline with the colour.RGB_to_RGB definition:
def XYZ_to_RGB(
XYZ: ArrayLike,
colourspace: RGB_Colourspace | None = None,
illuminant: ArrayLike | None = None,
chromatic_adaptation_transform: Literal["Bianco 2010", "Bianco PC 2010", "Bradford", "CAT02 Brill 2008", "CAT02", "CAT16", "CMCCAT2000", "CMCCAT97", "Fairchild", "Sharp", "Von Kries", "XYZ Scaling"] | str = "CAT02",
apply_cctf_encoding: bool = False,
**kwargs,
) -> NDArrayFloat:
...Full Arguments
The usage would be as follows:
XYZ_to_RGB(
XYZ,
colour.models.RGB_COLOURSPACE_ARRI_WIDE_GAMUT_4,
colour.CCS_ILLUMINANTS["cie_2_1931"]["D65"],
"Bradford",
True,
)Compared with:
XYZ_to_RGB(
XYZ,
colour.CCS_ILLUMINANTS["cie_2_1931"]["D65"],
colour.models.RGB_COLOURSPACE_ARRI_WIDE_GAMUT_4.whitepoint,
colour.models.RGB_COLOURSPACE_ARRI_WIDE_GAMUT_4.matrix_XYZ_to_RGB,
"Bradford",
colour.models.RGB_COLOURSPACE_ARRI_WIDE_GAMUT_4.cctf_encoding,
)No Chromatic Adaptation
If no chromatic adaptation is desired, this should be enough:
XYZ_to_RGB(
XYZ,
colour.models.RGB_COLOURSPACE_ARRI_WIDE_GAMUT_4,
)We could also support all the old arguments through **kwargs if required, they would override the various attributes of the RGB colourspace if passed and relevant, for example:
XYZ_to_RGB(
XYZ,
illuminant_XYZ=colour.CCS_ILLUMINANTS["cie_2_1931"]["D65"],
illuminant_RGB=colour.models.RGB_COLOURSPACE_ARRI_WIDE_GAMUT_4.whitepoint,
matrix_XYZ_to_RGB=colour.models.RGB_COLOURSPACE_ARRI_WIDE_GAMUT_4.matrix_XYZ_to_RGB,
chromatic_adaptation_transform="Bradford",
cctf_encoding=colour.models.RGB_COLOURSPACE_ARRI_WIDE_GAMUT_4.cctf_encoding,
)This is obviously a breaking change but it can be handled easily with warnings for transition, keen to hear what people think?