# SPDX-FileCopyrightText: 2017 Michael McWethy for Adafruit Industries
#
# SPDX-License-Identifier: MIT
"""
`colorutility`
====================================================
Helper functions for color calculations
* Author(s): Michael McWethy
"""
__version__ = "0.0.0+auto.0"
__repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_APDS9960.git"
[docs]
def calculate_color_temperature(r: int, g: int, b: int) -> float:
"""Converts the raw R/G/B values to color temperature in degrees Kelvin"""
# 1. Map RGB values to their XYZ counterparts.
# Based on 6500K fluorescent, 3000K fluorescent
# and 60W incandescent values for a wide range.
# Note: Y = Illuminance or lux
x = (-0.14282 * r) + (1.54924 * g) + (-0.95641 * b)
y = (-0.32466 * r) + (1.57837 * g) + (-0.73191 * b)
z = (-0.68202 * r) + (0.77073 * g) + (0.56332 * b)
# 2. Calculate the chromaticity co-ordinates
xchrome = x / (x + y + z)
ychrome = y / (x + y + z)
# 3. Use to determine the CCT
n = (xchrome - 0.3320) / (0.1858 - ychrome)
# 4. Calculate the final CCT
cct = (449.0 * pow(n, 3)) + (3525.0 * pow(n, 2)) + (6823.3 * n) + 5520.33
# Return the results in degrees Kelvin
return cct
[docs]
def calculate_lux(r: int, g: int, b: int) -> float:
"""Calculate ambient light values"""
# This only uses RGB ... how can we integrate clear or calculate lux
# based exclusively on clear since this might be more reliable?
illuminance = (-0.32466 * r) + (1.57837 * g) + (-0.73191 * b)
return illuminance