Ensure that colour.io.as_3_channels_image definition handles more e…

…xotic cases.

colour/io/image.py

@@ -914,14 +914,25 @@ def as_3_channels_image(a: ArrayLike) -> NDArrayFloat:
     array([[[ 0.18,  0.18,  0.18]]])
     >>> as_3_channels_image([[[0.18, 0.18, 0.18]]])
     array([[[ 0.18,  0.18,  0.18]]])
+    >>> as_3_channels_image([[[[0.18, 0.18, 0.18]]]])
+    array([[[ 0.18,  0.18,  0.18]]])
     """
 
-    a = as_float_array(a)
+    a = np.squeeze(as_float_array(a))
 
-    if len(a.shape) == 0:
-        a = tstack([a, a, a])
+    if len(a.shape) > 3:
+        raise ValueError(
+            "Array has more than 3-dimensions and cannot be converted to a "
+            "3-channels image-like representation!"
+        )
+
+    if len(a.shape) > 0 and a.shape[-1] not in (1, 3):
+        raise ValueError(
+            "Array has more than 1 or 3 channels and cannot be converted to a "
+            "3-channels image-like representation!"
+        )
 
-    if a.shape[-1] == 1:
+    if len(a.shape) == 0 or a.shape[-1] == 1:
         a = tstack([a, a, a])
 
     if len(a.shape) == 1:

colour/io/tests/test_image.py

@@ -8,6 +8,7 @@
 import tempfile
 
 import numpy as np
+import pytest
 
 from colour.constants import TOLERANCE_ABSOLUTE_TESTS
 from colour.io import (
@@ -594,3 +595,32 @@ def test_as_3_channels_image(self):
         np.testing.assert_equal(as_3_channels_image(a), b)
         a = np.array([[[0.18, 0.18, 0.18]]])
         np.testing.assert_equal(as_3_channels_image(a), b)
+        a = np.array([[[[0.18, 0.18, 0.18]]]])
+        np.testing.assert_equal(as_3_channels_image(a), b)
+
+    def test_raise_exception_as_3_channels_image(self):
+        """
+        Test :func:`colour.io.image.as_3_channels_image` definition raised
+        exception.
+        """
+
+        pytest.raises(
+            ValueError,
+            as_3_channels_image,
+            [
+                [
+                    [[0.18, 0.18, 0.18], [0.18, 0.18, 0.18]],
+                    [[0.18, 0.18, 0.18], [0.18, 0.18, 0.18]],
+                ],
+                [
+                    [[0.18, 0.18, 0.18], [0.18, 0.18, 0.18]],
+                    [[0.18, 0.18, 0.18], [0.18, 0.18, 0.18]],
+                ],
+            ],
+        )
+
+        pytest.raises(
+            ValueError,
+            as_3_channels_image,
+            [0.18, 0.18, 0.18, 0.18],
+        )