Ensure that interpolation is in [0, 1], fixes #624 (#660)

* Ensure that interpolation is in [0, 1], fixes #624

* Bump to 1.17.1

* Add assert

* Interpolate via HSV space

* Add test

custom_components/adaptive_lighting/manifest.json

@@ -8,5 +8,5 @@
   "iot_class": "calculated",
   "issue_tracker": "https://github.com/basnijholt/adaptive-lighting/issues",
   "requirements": ["ulid-transform"],
-  "version": "1.17.0"
+  "version": "1.17.1"
 }

custom_components/adaptive_lighting/switch.py

@@ -4,6 +4,7 @@ from __future__ import annotations
 import asyncio
 import base64
 import bisect
+import colorsys
 import datetime
 import functools
 import logging
@@ -1549,18 +1550,31 @@ class SimpleSwitch(SwitchEntity, RestoreEntity):
         self._state = False
 
 
-def lerp_color(
+def lerp_color_hsv(
     rgb1: tuple[int, int, int],
     rgb2: tuple[int, int, int],
     t: float,
 ) -> tuple[int, int, int]:
-    """Linearly interpolate between two RGB colors."""
-    return (
-        int(rgb1[0] + t * (rgb2[0] - rgb1[0])),
-        int(rgb1[1] + t * (rgb2[1] - rgb1[1])),
-        int(rgb1[2] + t * (rgb2[2] - rgb1[2])),
+    """Linearly interpolate between two RGB colors in HSV color space."""
+    t = abs(t)
+    assert 0 <= t <= 1
+
+    # Convert RGB to HSV
+    hsv1 = colorsys.rgb_to_hsv(*[x / 255.0 for x in rgb1])
+    hsv2 = colorsys.rgb_to_hsv(*[x / 255.0 for x in rgb2])
+
+    # Linear interpolation in HSV space
+    hsv = (
+        hsv1[0] + t * (hsv2[0] - hsv1[0]),
+        hsv1[1] + t * (hsv2[1] - hsv1[1]),
+        hsv1[2] + t * (hsv2[2] - hsv1[2]),
     )
 
+    # Convert back to RGB
+    rgb = tuple(int(round(x * 255)) for x in colorsys.hsv_to_rgb(*hsv))
+    assert all(0 <= x <= 255 for x in rgb), f"Invalid RGB color: {rgb}"
+    return rgb
+
 
 @dataclass(frozen=True)
 class SunLightSettings:
@@ -1748,7 +1762,7 @@ class SunLightSettings:
             # This will result in a perceptible jump in color at sunset and sunrise
             # because the `color_temperature_to_rgb` function is not 100% accurate.
             min_color_rgb = color_temperature_to_rgb(self.min_color_temp)
-            rgb_color = lerp_color(min_color_rgb, self.sleep_rgb_color, percent)
+            rgb_color = lerp_color_hsv(min_color_rgb, self.sleep_rgb_color, percent)
             color_temp_kelvin = self.calc_color_temp_kelvin(percent)
             force_rgb_color = True
         else:

tests/test_switch.py

@@ -92,6 +92,7 @@ from custom_components.adaptive_lighting.switch import (
     create_context,
     is_our_context,
     is_our_context_id,
+    lerp_color_hsv,
 )
 
 _LOGGER = logging.getLogger(__name__)
@@ -1701,3 +1702,19 @@ async def test_adapt_until_sleep_and_rgb_colors(hass):
     await switch._update_attrs_and_maybe_adapt_lights(context=context)
     assert switch._settings[ATTR_BRIGHTNESS_PCT] == DEFAULT_SLEEP_BRIGHTNESS
     assert switch._settings["rgb_color"] == DEFAULT_SLEEP_RGB_COLOR
+
+
+def test_lerp_color_hsv():
+    assert lerp_color_hsv((255, 0, 0), (0, 255, 0), 0) == (255, 0, 0)
+    assert lerp_color_hsv((255, 0, 0), (0, 255, 0), 1) == (0, 255, 0)
+    assert lerp_color_hsv((255, 0, 0), (0, 255, 0), 0.5) == (255, 255, 0)
+    assert lerp_color_hsv((0, 0, 255), (255, 255, 255), 0.5) == (128, 255, 128)
+
+    # Tests that the interpolation is consistent
+    for t in [0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1]:
+        color = lerp_color_hsv((255, 0, 0), (0, 255, 0), t)
+        inverted_color = lerp_color_hsv((0, 255, 0), (255, 0, 0), 1 - t)
+        assert color == inverted_color
+
+    with pytest.raises(AssertionError):
+        lerp_color_hsv((255, 0, 0), (0, 255, 0), 1.1)