Bugfix: HSL color ordering in ManimColor (#4202)

* Bugfix: colorsys uses HLS (hue, luminance, saturation) ordering when converting to/from rgb. Manim says it uses HSL ordering. Fixed order of parameters in call to colorsys for ManimColor.from_hsl and ManimColor.to_hsl.
Added tests ensure correct HSL ordering.

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Update to fix the correct color tests

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

---------

Co-authored-by: SonnyRoomex <[email protected]>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Aarush Deshpande <[email protected]>

Author: 4 people

manim/utils/color/core.py

@@ -601,7 +601,8 @@ def to_hsl(self) -> HSL_Array_Float:
         HSL_Array_Float
             An HSL array of 3 floats from 0.0 to 1.0.
         """
-        return np.array(colorsys.rgb_to_hls(*self.to_rgb()))
+        hls = colorsys.rgb_to_hls(*self.to_rgb())
+        return np.array([hls[0], hls[2], hls[1]])
 
     def invert(self, with_alpha: bool = False) -> Self:
         """Return a new, linearly inverted version of this :class:`ManimColor` (no
@@ -906,7 +907,7 @@ def from_hsl(
             The :class:`ManimColor` with the corresponding RGB values to the given HSL
             array.
         """
-        rgb = colorsys.hls_to_rgb(*hsl)
+        rgb = colorsys.hls_to_rgb(hsl[0], hsl[2], hsl[1])
         return cls._from_internal(ManimColor(rgb, alpha)._internal_value)
 
     @overload

tests/module/utils/test_manim_color.py

@@ -116,9 +116,19 @@ def test_to_hsv() -> None:
 
 def test_to_hsl() -> None:
     color = ManimColor((0x1, 0x2, 0x3, 0x4))
-    nt.assert_array_equal(
-        color.to_hsl(), colorsys.rgb_to_hls(0x1 / 255, 0x2 / 255, 0x3 / 255)
-    )
+    hls = colorsys.rgb_to_hls(0x1 / 255, 0x2 / 255, 0x3 / 255)
+
+    nt.assert_array_equal(color.to_hsl(), np.array([hls[0], hls[2], hls[1]]))
+
+
+def test_from_hsl() -> None:
+    hls = colorsys.rgb_to_hls(0x1 / 255, 0x2 / 255, 0x3 / 255)
+    hsl = np.array([hls[0], hls[2], hls[1]])
+
+    color = ManimColor.from_hsl(hsl)
+    rgb = np.array([0x1 / 255, 0x2 / 255, 0x3 / 255])
+
+    nt.assert_allclose(color.to_rgb(), rgb)
 
 
 def test_invert() -> None: