Add stable fallback for low-color artwork

luz-musica.py

@@ -28,6 +28,14 @@ OKLCH_LIGHTNESS = 0.72
 OKLCH_CHROMA = 0.24
 MAX_BRIGHTNESS_STEP = 0.10
 PLAYERCTL_BIN = os.environ.get("PLAYERCTL_BIN", "playerctl")
+YELLOW_HUE_START = 0.12
+YELLOW_HUE_END = 0.18
+AMBER_TARGET_HUE = 0.10
+YELLOW_CHROMA_SCALE = 0.82
+YELLOW_LIGHTNESS_SCALE = 0.94
+NEUTRAL_CHROMA_THRESHOLD = 0.05
+NEUTRAL_SATURATION_THRESHOLD = 0.18
+PURPLE_FALLBACK_HUE = 0.78
 
 
 def run_playerctl(field: str, player: str | None = None) -> str:
@@ -176,6 +184,16 @@ def hsv_to_rgb(h: float, s: float, v: float) -> tuple[int, int, int]:
     return (int(r * 255), int(g * 255), int(b * 255))
 
 
+def tame_yellow_oklch(lightness: float, chroma: float, hue: float) -> tuple[float, float, float]:
+    if YELLOW_HUE_START <= hue <= YELLOW_HUE_END:
+        return (
+            lightness * YELLOW_LIGHTNESS_SCALE,
+            chroma * YELLOW_CHROMA_SCALE,
+            AMBER_TARGET_HUE,
+        )
+    return (lightness, chroma, hue)
+
+
 def srgb_channel_to_linear(channel: float) -> float:
     if channel <= 0.04045:
         return channel / 12.92
@@ -244,12 +262,13 @@ def oklch_to_rgb(lightness: float, chroma: float, hue: float) -> tuple[int, int,
 
 def pure_tone_palette() -> list[tuple[int, int, int]]:
     return [
-        oklch_to_rgb(OKLCH_LIGHTNESS, OKLCH_CHROMA, index / PALETTE_SIZE)
+        oklch_to_rgb(*tame_yellow_oklch(OKLCH_LIGHTNESS, OKLCH_CHROMA, index / PALETTE_SIZE))
         for index in range(PALETTE_SIZE)
     ]
 
 
 PURE_TONE_PALETTE = pure_tone_palette()
+PURPLE_FALLBACK_RGB = oklch_to_rgb(OKLCH_LIGHTNESS, OKLCH_CHROMA, PURPLE_FALLBACK_HUE)
 
 
 def clamp_brightness(rgb: tuple[int, int, int], previous_rgb: tuple[int, int, int] | None) -> tuple[int, int, int]:
@@ -272,7 +291,7 @@ def snap_to_palette(rgb: tuple[int, int, int]) -> tuple[int, int, int]:
     )
 
     best_lightness, _, best_hue = rgb_to_oklch(best)
-    return oklch_to_rgb(best_lightness, OKLCH_CHROMA, best_hue)
+    return oklch_to_rgb(*tame_yellow_oklch(best_lightness, OKLCH_CHROMA, best_hue))
 
 
 def good_pixels(img: Image.Image) -> list[tuple[int, int, int]]:
@@ -297,16 +316,35 @@ def good_pixels(img: Image.Image) -> list[tuple[int, int, int]]:
     return filtered
 
 
+def color_information_score(pixels: list[tuple[int, int, int]]) -> tuple[float, float]:
+    if not pixels:
+        return (0.0, 0.0)
+
+    chroma_total = 0.0
+    saturation_total = 0.0
+    for pixel in pixels:
+        _, chroma, _ = rgb_to_oklch(pixel)
+        _, saturation, _ = rgb_to_hsv(pixel)
+        chroma_total += chroma
+        saturation_total += saturation
+
+    count = len(pixels)
+    return (chroma_total / count, saturation_total / count)
+
+
+def should_use_purple_fallback(pixels: list[tuple[int, int, int]]) -> bool:
+    avg_chroma, avg_saturation = color_information_score(pixels)
+    return avg_chroma < NEUTRAL_CHROMA_THRESHOLD or avg_saturation < NEUTRAL_SATURATION_THRESHOLD
+
+
 def dominant_color(img: Image.Image) -> tuple[int, int, int]:
     pixels = good_pixels(img)
     if not pixels:
         # fallback simples
-        small = img.resize((50, 50))
-        colors = small.getcolors(50 * 50)
-        if not colors:
-            return (255, 255, 255)
-        colors.sort(reverse=True)
-        return colors[0][1]
+        return PURPLE_FALLBACK_RGB
+
+    if should_use_purple_fallback(pixels):
+        return PURPLE_FALLBACK_RGB
 
     # Quantiza para agrupar tons parecidos
     buckets: dict[tuple[int, int, int], int] = {}