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73 lines
1.6 KiB
C
73 lines
1.6 KiB
C
#ifndef KELVINTORGB_H
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#define KELVINTORGB_H
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#include <cmath>
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#include <utils/ColorRgb.h>
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// Constants
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namespace {
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const int TEMPERATURE_MINIMUM = 1000;
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const int TEMPERATUR_MAXIMUM = 40000;
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} //End of constants
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static ColorRgb getRgbFromTemperature(int temperature)
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{
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//Temperature input in Kelvin valid in the range 1000 K to 40000 K. White light = 6600K
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temperature = qBound(TEMPERATURE_MINIMUM, temperature, TEMPERATUR_MAXIMUM);
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// All calculations require temperature / 100, so only do the conversion once.
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temperature /= 100;
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// Compute each color in turn.
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int red, green, blue;
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// red
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if (temperature <= 66)
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{
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red = 255;
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}
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else
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{
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// Note: the R-squared value for this approximation is 0.988.
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red = static_cast<int>(329.698727446 * (pow(temperature - 60, -0.1332047592)));
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}
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// green
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if (temperature <= 66)
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{
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// Note: the R-squared value for this approximation is 0.996.
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green = static_cast<int>(99.4708025861 * log(temperature) - 161.1195681661);
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}
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else
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{
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// Note: the R-squared value for this approximation is 0.987.
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green = static_cast<int>(288.1221695283 * (pow(temperature - 60, -0.0755148492)));
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}
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// blue
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if (temperature >= 66)
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{
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blue = 255;
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}
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else if (temperature <= 19)
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{
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blue = 0;
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}
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else
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{
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// Note: the R-squared value for this approximation is 0.998.
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blue = static_cast<int>(138.5177312231 * log(temperature - 10) - 305.0447927307);
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}
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return {
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static_cast<uint8_t>(qBound(0, red, 255)),
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static_cast<uint8_t>(qBound(0, green, 255)),
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static_cast<uint8_t>(qBound(0, blue, 255)),
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};
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}
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#endif // KELVINTORGB_H
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