add alternate SpectralShape constructor

Author: tjdcs

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:
     """