Modified the wavelength argument of colorsynth.rgb() to accept va…

…lues of `None`.

colorsynth/_colorsynth.py

@@ -660,7 +660,7 @@ def transform_spd_wavelength(x: np.ndarray, w: u.Quantity):
 
 def rgb(
     spd: np.ndarray,
-    wavelength: u.Quantity,
+    wavelength: None | u.Quantity = None,
     axis: int = -1,
     spd_min: None | np.ndarray = None,
     spd_max: None | np.ndarray = None,
@@ -678,7 +678,9 @@ def rgb(
     spd
         a spectral power distribution to be converted into a RGB array
     wavelength
-        the wavelength array corresponding to the spectral power distribution
+        The wavelength array corresponding to the spectral power distribution.
+        If :obj:`None`, the wavelength is assumed to be evenly sampled across
+        the human visible color range.
     axis
         the logical axis corresponding to changing wavelength,
         or the axis along which to integrate the spectral power distribution
@@ -700,7 +702,33 @@ def rgb(
     wavelength_norm
         an optional function to transform the wavelength values before they
         are mapped into the human visible color range.
+
+    Examples
+    --------
+    Colorize a random, 3D numpy array.
+
+    .. jupyter-execute::
+
+        import numpy as np
+        import matplotlib.pyplot as plt
+        import colorsynth
+
+        # Create a uniform random 3D numpy array
+        a = np.random.uniform(low=0, high=1, size=(16, 16, 11))
+
+        # Colorize the 3D numpy array
+        rgb = colorsynth.rgb(a)
+
+        # Plot the resulting RGB image
+        fig, ax = plt.subplots(constrained_layout=True)
+        ax.imshow(rgb);
     """
+    if wavelength is None:
+        shape_wavelength = [1] * spd.ndim
+        shape_wavelength[axis] = -1
+        wavelength = np.linspace(0, 1, num=spd.shape[axis])
+        wavelength = wavelength.reshape(shape_wavelength)
+
     spd, wavelength = np.broadcast_arrays(spd, wavelength, subok=True)
 
     transform_spd_wavelength = _transform_spd_wavelength(

colorsynth/_tests/test_colorsynth.py

@@ -146,6 +146,7 @@ def test_sRGB(
 @pytest.mark.parametrize(
     argnames="wavelength",
     argvalues=[
+        None,
         np.linspace(380, 780, num=101) * u.nm,
     ],
 )