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Kelvin to RGB in python
"""
Based on: http://www.tannerhelland.com/4435/convert-temperature-rgb-algorithm-code/
Comments resceived: https://gist.github.com/petrklus/b1f427accdf7438606a6
Original pseudo code:
Set Temperature = Temperature \ 100
Calculate Red:
If Temperature <= 66 Then
Red = 255
Else
Red = Temperature - 60
Red = 329.698727446 * (Red ^ -0.1332047592)
If Red < 0 Then Red = 0
If Red > 255 Then Red = 255
End If
Calculate Green:
If Temperature <= 66 Then
Green = Temperature
Green = 99.4708025861 * Ln(Green) - 161.1195681661
If Green < 0 Then Green = 0
If Green > 255 Then Green = 255
Else
Green = Temperature - 60
Green = 288.1221695283 * (Green ^ -0.0755148492)
If Green < 0 Then Green = 0
If Green > 255 Then Green = 255
End If
Calculate Blue:
If Temperature >= 66 Then
Blue = 255
Else
If Temperature <= 19 Then
Blue = 0
Else
Blue = Temperature - 10
Blue = 138.5177312231 * Ln(Blue) - 305.0447927307
If Blue < 0 Then Blue = 0
If Blue > 255 Then Blue = 255
End If
End If
"""
import math
def convert_K_to_RGB(colour_temperature):
"""
Converts from K to RGB, algorithm courtesy of
http://www.tannerhelland.com/4435/convert-temperature-rgb-algorithm-code/
"""
#range check
if colour_temperature < 1000:
colour_temperature = 1000
elif colour_temperature > 40000:
colour_temperature = 40000
tmp_internal = colour_temperature / 100.0
# red
if tmp_internal <= 66:
red = 255
else:
tmp_red = 329.698727446 * math.pow(tmp_internal - 60, -0.1332047592)
if tmp_red < 0:
red = 0
elif tmp_red > 255:
red = 255
else:
red = tmp_red
# green
if tmp_internal <=66:
tmp_green = 99.4708025861 * math.log(tmp_internal) - 161.1195681661
if tmp_green < 0:
green = 0
elif tmp_green > 255:
green = 255
else:
green = tmp_green
else:
tmp_green = 288.1221695283 * math.pow(tmp_internal - 60, -0.0755148492)
if tmp_green < 0:
green = 0
elif tmp_green > 255:
green = 255
else:
green = tmp_green
# blue
if tmp_internal >=66:
blue = 255
elif tmp_internal <= 19:
blue = 0
else:
tmp_blue = 138.5177312231 * math.log(tmp_internal - 10) - 305.0447927307
if tmp_blue < 0:
blue = 0
elif tmp_blue > 255:
blue = 255
else:
blue = tmp_blue
return red, green, blue
if __name__ == "__main__":
print("Preview requires matplotlib")
from matplotlib import pyplot as plt
step_size = 100
for i in range(0, 15000, step_size):
color = list(map(lambda div: div/255.0, convert_K_to_RGB(i))) + [1]
print(color)
plt.plot((i, i), (0, 1), linewidth=step_size/2.0, linestyle="-", color=color)
plt.show()

sbremer commented Nov 9, 2016

Awesome, thanks :)

Thank you so much for this!

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