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colortemp.go
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/
colortemp.go
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package main
import (
"log"
"math"
"time"
hue "github.com/benburwell/gohue"
"github.com/cpucycle/astrotime"
)
type ColorTemperature uint
// Get the correct color temperature for a given time. If the time is between
// sunrise and sunset, a high CT is selected. Otherise, during night, a low
// color temperature is used.
//
// TODO: This is a naive approach and should be revisited
func getDesiredColorTemperature(t time.Time, latitude, longitude float64) ColorTemperature {
log.Printf("Calculating sunrise/sunset for: %s\n", t.Format(time.RFC3339))
sunrise := astrotime.CalcSunrise(t, latitude, longitude)
sunset := astrotime.CalcSunset(t, latitude, longitude)
log.Printf("Sunrise: %s, Sunset: %s\n", sunrise.Format(time.RFC3339), sunset.Format(time.RFC3339))
if t.After(sunrise) && t.Before(sunset) {
log.Println("Daytime, setting high CT")
return 6500
} else {
log.Println("Nighttime, setting low CT")
return 1800
}
}
// Translate a desired color temperature in Kelvins to a value comprehensible
// by a Hue luminaire. According to Hue documentation, the value 153
// corresponds to 6500K, and 500 corresponds to 2000K. Using these known
// values, we'll create a mapping between spaces, and additionally limit the
// resulting value by the range that the luminaire supports.
//
// 153 <=> 6500K
// 500 <=> 2000K
// =============
// 347 4500
func (ct ColorTemperature) TranslateForLight(light hue.Light) uint16 {
divisor := 12.968
scaled := float64(ct) / divisor
inverted := 500 - scaled + 153
min := float64(light.Capabilities.Control.CT.Min)
max := float64(light.Capabilities.Control.CT.Max)
return uint16(math.Max(min, math.Min(max, inverted)))
}
// Determine whether there is a non-zero color temperature range for the given light
func supportsColorTemp(l hue.Light) bool {
return l.Capabilities.Control.CT.Max > l.Capabilities.Control.CT.Min
}