Correctly calculate average color for light groups in HS Color Mode (home-assistant#154678)

Author: ogruendel

homeassistant/components/group/light.py

@@ -55,7 +55,7 @@
 from homeassistant.helpers.typing import ConfigType, DiscoveryInfoType
 
 from .entity import GroupEntity
-from .util import find_state_attributes, mean_tuple, reduce_attribute
+from .util import find_state_attributes, mean_circle, mean_tuple, reduce_attribute
 
 DEFAULT_NAME = "Light Group"
 CONF_ALL = "all"
@@ -229,7 +229,7 @@ def async_update_group_state(self) -> None:
         self._attr_brightness = reduce_attribute(on_states, ATTR_BRIGHTNESS)
 
         self._attr_hs_color = reduce_attribute(
-            on_states, ATTR_HS_COLOR, reduce=mean_tuple
+            on_states, ATTR_HS_COLOR, reduce=mean_circle
         )
         self._attr_rgb_color = reduce_attribute(
             on_states, ATTR_RGB_COLOR, reduce=mean_tuple

homeassistant/components/group/util.py

@@ -4,6 +4,7 @@
 
 from collections.abc import Callable, Iterator
 from itertools import groupby
+from math import atan2, cos, degrees, radians, sin
 from typing import Any
 
 from homeassistant.core import State
@@ -32,6 +33,23 @@ def mean_tuple(*args: Any) -> tuple[float | Any, ...]:
     return tuple(sum(x) / len(x) for x in zip(*args, strict=False))
 
 
+def mean_circle(*args: Any) -> tuple[float | Any, ...]:
+    """Return the circular mean of hue values and arithmetic mean of saturation values from HS color tuples."""
+    if not args:
+        return ()
+
+    hues, saturations = zip(*args, strict=False)
+
+    sum_x = sum(cos(radians(h)) for h in hues)
+    sum_y = sum(sin(radians(h)) for h in hues)
+
+    mean_angle = degrees(atan2(sum_y, sum_x)) % 360
+
+    saturation = sum(saturations) / len(saturations)
+
+    return (mean_angle, saturation)
+
+
 def attribute_equal(states: list[State], key: str) -> bool:
     """Return True if all attributes found matching key from states are equal.
 

tests/components/group/test_light.py

@@ -404,6 +404,33 @@ async def test_color_hs(hass: HomeAssistant) -> None:
     assert state.attributes[ATTR_SUPPORTED_COLOR_MODES] == ["hs"]
     assert state.attributes[ATTR_SUPPORTED_FEATURES] == 0
 
+    await hass.services.async_call(
+        "light",
+        "turn_on",
+        {"entity_id": [entity0.entity_id], ATTR_HS_COLOR: (355, 100)},
+        blocking=True,
+    )
+
+    await hass.async_block_till_done()
+    state = hass.states.get("light.light_group")
+    assert state.attributes[ATTR_COLOR_MODE] == "hs"
+    assert state.attributes[ATTR_HS_COLOR] == (357.5, 75)
+    assert state.attributes[ATTR_SUPPORTED_COLOR_MODES] == ["hs"]
+    assert state.attributes[ATTR_SUPPORTED_FEATURES] == 0
+
+    await hass.services.async_call(
+        "light",
+        "turn_on",
+        {"entity_id": [entity1.entity_id], ATTR_HS_COLOR: (5, 90)},
+        blocking=True,
+    )
+    await hass.async_block_till_done()
+    state = hass.states.get("light.light_group")
+    assert state.attributes[ATTR_COLOR_MODE] == "hs"
+    assert state.attributes[ATTR_HS_COLOR] == (360, 95)
+    assert state.attributes[ATTR_SUPPORTED_COLOR_MODES] == ["hs"]
+    assert state.attributes[ATTR_SUPPORTED_FEATURES] == 0
+
 
 async def test_color_rgb(hass: HomeAssistant) -> None:
     """Test rgbw color reporting."""