115 lines
4.2 KiB
Python
115 lines
4.2 KiB
Python
"""日出日落时间计算（NOAA 简化算法）与白天/夜晚判定。
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用于"自动"主题模式：根据用户天气配置的经纬度 + 本地时区，判断当前
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时刻处于白天（浅色主题）还是夜晚（深色主题）。
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算法来源：Ed Williams《Sunrise/Sunset Algorithm》
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(https://edwilliams.org/sunrise_sunset_algorithm.htm)
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"""
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import math
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from datetime import datetime, timezone, timedelta
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# 太阳天顶角：日出日落定义（含大气折射）
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ZENITH = 90.833
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def _day_of_year(dt: datetime) -> int:
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"""计算一年中的第几天（NOAA 公式）。"""
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y, m, d = dt.year, dt.month, dt.day
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n1 = math.floor(275 * m / 9)
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n2 = math.floor((m + 9) / 12)
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n3 = 1 + math.floor((y - 4 * math.floor(y / 4) + 2) / 3)
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return n1 - (n2 * n3) + d - 30
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def _hour_angle(lat: float, lon: float, day_of_year: int, is_sunrise: bool) -> float | None:
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"""返回日出/日落的 UTC 小时（0~24），None 表示极昼/极夜（当天无日出日落）。"""
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lng_hour = lon / 15.0
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if is_sunrise:
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t = day_of_year + ((6 - lng_hour) / 24.0)
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else:
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t = day_of_year + ((18 - lng_hour) / 24.0)
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m = (0.9856 * t) - 3.289
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l = (m + 1.916 * math.sin(math.radians(m))
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+ 0.020 * math.sin(math.radians(2 * m)) + 282.634) % 360
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ra = math.degrees(math.atan(0.91764 * math.tan(math.radians(l)))) % 360
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# 校正 RA 象限
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l_quad = math.floor(l / 90) * 90
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ra_quad = math.floor(ra / 90) * 90
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ra = ra + (l_quad - ra_quad)
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ra /= 15.0 # 转为小时
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sin_dec = 0.39782 * math.sin(math.radians(l))
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cos_dec = math.cos(math.asin(sin_dec))
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cos_h = ((math.cos(math.radians(ZENITH)) - sin_dec * math.sin(math.radians(lat)))
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/ (cos_dec * math.cos(math.radians(lat))))
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if cos_h > 1 or cos_h < -1:
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return None # 极昼/极夜
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if is_sunrise:
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h = 360 - math.degrees(math.acos(cos_h))
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else:
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h = math.degrees(math.acos(cos_h))
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h /= 15.0
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# NOAA：T = H + RA - 0.06571*t - 6.622（小时），UT = T - lngHour（mod 24）
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local_t = h + ra - 0.06571 * t - 6.622
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return (local_t - lng_hour) % 24.0
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def sun_times_utc(lat: float, lon: float, date: datetime) -> tuple[datetime | None, datetime | None]:
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"""返回 (日出UTC, 日落UTC)，极昼/极夜时对应项为 None。
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date 为任意带时区 datetime（取其日期）。"""
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lat = float(lat)
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lon = float(lon)
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day = _day_of_year(date.astimezone(timezone.utc))
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sunrise_h = _hour_angle(lat, lon, day, True)
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sunset_h = _hour_angle(lat, lon, day, False)
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if sunrise_h is None and sunset_h is None:
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return None, None # 极昼或极夜，调用方按本地小时粗判
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def to_utc(h: float) -> datetime:
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base = date.astimezone(timezone.utc).replace(hour=0, minute=0, second=0, microsecond=0)
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return base + timedelta(hours=h)
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sunrise = to_utc(sunrise_h) if sunrise_h is not None else None
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sunset = to_utc(sunset_h) if sunset_h is not None else None
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return sunrise, sunset
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def is_daytime(lat: float, lon: float, now_local: datetime) -> bool:
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"""判断本地时刻是否为白天。
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now_local 为带时区的本地 datetime（使用用户配置时区）。
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用 UTC 小时比较（忽略日期归属），自动处理日出/日落跨 UTC 午夜的情况。
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"""
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now_utc = now_local.astimezone(timezone.utc)
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sunrise, sunset = sun_times_utc(lat, lon, now_local)
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if sunrise is None or sunset is None:
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# 极昼/极夜：根据本地小时粗判（6-18 视为白天）
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return 6 <= now_local.hour < 18
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sr_h = sunrise.hour + sunrise.minute / 60.0
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ss_h = sunset.hour + sunset.minute / 60.0
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now_h = now_utc.hour + now_utc.minute / 60.0
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if ss_h < sr_h:
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ss_h += 24.0 # 跨 UTC 午夜（东半球）
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if now_h < sr_h:
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now_h += 24.0
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return sr_h <= now_h <= ss_h
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def day_fraction_today(lat: float, lon: float, now_local: datetime) -> float:
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"""当天白昼占全天比例（0~1），用于自动模式的平滑切换（预留）。"""
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sunrise, sunset = sun_times_utc(lat, lon, now_local)
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if sunrise is None or sunset is None:
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return 0.5
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total = (sunset - sunrise).total_seconds()
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return max(0.0, min(1.0, total / 86400.0))
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