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108 lines
2.6 KiB
C++
108 lines
2.6 KiB
C++
//
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// FILE: Kelvin2RGB.cpp
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// AUTHOR: Rob Tillaart
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// VERSION: 0.1.0
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// DATE: 2018-01-31
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// PURPOSE: Arduino library for converting temperature to RGB values
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// URL: https://github.com/RobTillaart/Kelvin2RGB
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#include "Kelvin2RGB.h"
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#define DIVIDE_255 0.0039215686274509803921568627451
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Kelvin2RGB::Kelvin2RGB()
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{
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_temperature = 0;
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_brightness = 0; // default = darkness
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_red = 0;
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_green = 0;
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_blue = 0;
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}
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void Kelvin2RGB::begin()
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{
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}
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// Tanner Helland formulas
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void Kelvin2RGB::convert_TH(float temperature, float brightness)
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{
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_temperature = constrain(temperature, 0, 65500);
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_brightness = constrain(brightness, 0, 100);
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_red = _green = _blue = 0;
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float t = _temperature * 0.01;
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if (t <= 66)
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{
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_red = 255;
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_green = (99.4708025861 * log(t)) - 161.1195681661;
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if (t > 19)
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{
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_blue = (138.5177312231 * log(t - 10)) - 305.0447927307;
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}
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else _blue = 0;
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}
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else
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{
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_red = 329.698727466 * pow(t - 60, -0.1332047592);
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_green = 288.1221695283 * pow(t - 60, -0.0755148492);
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_blue = 255;
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}
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float f = 0.01 * _brightness;
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_red = constrain(f * _red, 0, 255);
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_green = constrain(f * _green, 0, 255);
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_blue = constrain(f * _blue, 0, 255);
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_rgb = round(_red) * 65536UL + round(_green) * 256UL + round(_blue);
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// divide by 255 to get factors between 0..1
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_red *= DIVIDE_255;
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_green *= DIVIDE_255;
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_blue *= DIVIDE_255;
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}
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// Neil Bartlett formulas
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void Kelvin2RGB::convert_NB(float temperature, float brightness)
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{
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_temperature = constrain(temperature, 0, 65500);
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_brightness = constrain(brightness, 0, 100);
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_red = _green = _blue = 0;
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float t = _temperature * 0.01;
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if (t <= 66)
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{
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_red = 255;
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_green = t - 2;
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_green = -155.25485562709179 - 0.44596950469579133 * _green + 104.49216199393888 * log(_green);
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_blue = 0;
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if (t > 20)
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{
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_blue = t - 10;
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_blue = -254.76935184120902 + 0.8274096064007395 * _blue + 115.67994401066147 * log(_blue);
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}
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}
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else
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{
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_red = t - 55.0;
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_red = 351.97690566805693 + 0.114206453784165 * _red - 40.25366309332127 * log(_red);
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_green = t - 50.0;
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_green = 325.4494125711974 + 0.07943456536662342 * _green - 28.0852963507957 * log(_green);
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_blue = 255;
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}
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float f = 0.01 * _brightness;
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_red = constrain(f * _red, 0, 255);
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_green = constrain(f * _green, 0, 255);
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_blue = constrain(f * _blue, 0, 255);
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_rgb = round(_red) * 65536UL + round(_green) * 256UL + round(_blue);
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// divide by 255 to get factors between 0..1
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_red *= DIVIDE_255;
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_green *= DIVIDE_255;
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_blue *= DIVIDE_255;
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}
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// -- END OF FILE --
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