PR: Add colour.SpectralShape.from_array class method (constructor).

.pre-commit-config.yaml

@@ -1,3 +1,10 @@
+# The pre-commit steps used by colour are:
+# * codespell
+# * isort
+# * ruff-format
+# * ruff --fix
+# * blacken-docs
+# * prettier (with specific fixes)
 repos:
   - repo: https://github.com/pre-commit/pre-commit-hooks
     rev: "v5.0.0"

colour/colorimetry/spectrum.py

@@ -158,6 +158,29 @@ def __init__(self, start: Real, end: Real, interval: Real) -> None:
         self.end = end
         self.interval = interval
 
+    @classmethod
+    def from_array(cls, data: ArrayLike) -> SpectralShape:
+        """Alternate constructor, create a SpectralShape from an ArrayLike list
+        of values. Values must be evenly spaced.
+
+        Parameters
+        ----------
+        data : ArrayLike
+            The wavelength list
+
+        Returns
+        -------
+        SpectralShape
+        """
+        data = np.asarray(data)
+
+        spacing = (diff_intermediate := np.diff(data))[0]
+        if ~np.all(diff_intermediate == spacing):
+            error = "data values must have equal spacing"
+            raise RuntimeError(error)
+
+        return SpectralShape(data[0], data[-1], spacing)
+
     @property
     def start(self) -> Real:
         """

colour/colorimetry/tests/test_spectrum.py

@@ -1417,6 +1417,21 @@ def test_range(self) -> None:
             np.arange(0, 10 + 0.1, 0.1),
         )
 
+    def test_from_data(self) -> None:
+        """Test :func:`colour.colorimetry.spectrum.SpectralShape.from_array`"""
+        data = np.arange(400, 700 + 1, 10)  # arange generates [start, stop)
+        shape = SpectralShape.from_array(data)
+
+        assert shape.start == 400
+        assert shape.end == 700
+        assert shape.interval == 10
+
+        assert shape == SpectralShape(400, 700, 10)
+
+        with pytest.raises(RuntimeError):
+            data = [400, 450, 500, 555, 600, 650, 700]
+            SpectralShape.from_array(data)
+
 
 class TestSpectralDistribution:
     """

colour/quality/cfi2017.py

@@ -42,7 +42,8 @@
 if typing.TYPE_CHECKING:
     from colour.hints import ArrayLike, List, Literal, Tuple
 
-from colour.hints import NDArrayFloat, cast
+from colour.colorimetry.spectrum import SPECTRAL_SHAPE_DEFAULT
+from colour.hints import ArrayLike, List, NDArrayFloat, Tuple, cast
 from colour.models import JMh_CIECAM02_to_CAM02UCS, UCS_to_uv, XYZ_to_UCS
 from colour.temperature import CCT_to_xy_CIE_D, uv_to_CCT_Ohno2013
 from colour.utilities import (
@@ -66,16 +67,16 @@
 __status__ = "Production"
 
 __all__ = [
-    "SPECTRAL_SHAPE_CIE2017",
     "ROOT_RESOURCES_CIE2017",
-    "DataColorimetry_TCS_CIE2017",
+    "SPECTRAL_SHAPE_CIE2017",
+    "CCT_reference_illuminant",
     "ColourRendering_Specification_CIE2017",
+    "DataColorimetry_TCS_CIE2017",
     "colour_fidelity_index_CIE2017",
+    "delta_E_to_R_f",
     "load_TCS_CIE2017",
-    "CCT_reference_illuminant",
     "sd_reference_illuminant",
     "tcs_colorimetry_data",
-    "delta_E_to_R_f",
 ]
 
 SPECTRAL_SHAPE_CIE2017: SpectralShape = SpectralShape(380, 780, 1)
@@ -346,7 +347,9 @@ def CCT_reference_illuminant(sd: SpectralDistribution) -> NDArrayFloat:
     return uv_to_CCT_Ohno2013(UCS_to_uv(XYZ_to_UCS(XYZ)), start=1000, end=25000)
 
 
-def sd_reference_illuminant(CCT: float, shape: SpectralShape) -> SpectralDistribution:
+def sd_reference_illuminant(
+    CCT: float, shape: SpectralShape = SPECTRAL_SHAPE_DEFAULT
+) -> SpectralDistribution:
     """
     Compute the reference illuminant for a given correlated colour temperature
     :math:`T_{cp}` for use in *CIE 2017 Colour Fidelity Index* (CFI)
@@ -357,7 +360,8 @@ def sd_reference_illuminant(CCT: float, shape: SpectralShape) -> SpectralDistrib
     CCT
         Correlated colour temperature :math:`T_{cp}`.
     shape
-        Desired shape of the returned spectral distribution.
+        Desired shape of the returned spectral distribution. Defaults to
+        SPECTRAL_SHAPE_DEFAULT
 
     Returns
     -------

colour/quality/tests/test_cfi2017.py

@@ -19,6 +19,7 @@
     reshape_sd,
     sd_blackbody,
 )
+from colour.colorimetry.spectrum import SPECTRAL_SHAPE_DEFAULT
 from colour.quality.cfi2017 import (
     CCT_reference_illuminant,
     colour_fidelity_index_CIE2017,
@@ -924,6 +925,14 @@ class TestSdReferenceIlluminant:
     definition unit tests methods.
     """
 
+    def test_default_args(self) -> None:
+        """Test :func:`color.quality.CIE2017.sd_reference_illuminant` for
+        default shape argument.
+        """
+
+        sd = sd_reference_illuminant(5421)
+        assert sd.shape == SPECTRAL_SHAPE_DEFAULT
+
     def test_sd_reference_illuminant(self) -> None:
         """
         Test :func:`colour.quality.CIE2017.sd_reference_illuminant`