* Copyright 2024, Haiku, Inc. All rights reserved.
* Distributed under the terms of the MIT License.
*/
#include <HSL.h>
hsl_color
hsl_color::from_rgb(const rgb_color& rgb)
{
hsl_color result;
float r = rgb.red / 255.0f;
float g = rgb.green / 255.0f;
float b = rgb.blue / 255.0f;
float max = max_c(max_c(r, g), b);
float min = min_c(min_c(r, g), b);
result.hue = result.saturation = result.lightness = (max + min) / 2;
if (max == min) {
result.hue = result.saturation = 0;
} else {
float diff = max - min;
result.saturation
= (result.lightness > 0.5) ? (diff / (2 - max - min)) : (diff / (max + min));
if (max == r)
result.hue = (g - b) / diff + (g < b ? 6 : 0);
else if (max == g)
result.hue = (b - r) / diff + 2;
else if (max == b)
result.hue = (r - g) / diff + 4;
result.hue /= 6;
}
return result;
}
rgb_color
hsl_color::to_rgb() const
{
rgb_color result;
result.alpha = 255;
if (saturation == 0) {
result.red = result.green = result.blue = uint8(lightness * 255);
} else {
float q = lightness < 0.5 ? (lightness * (1 + saturation))
: (lightness + saturation - lightness * saturation);
float p = 2 * lightness - q;
result.red = uint8(hue_to_rgb(p, q, hue + 1./3) * 255);
result.green = uint8(hue_to_rgb(p, q, hue) * 255);
result.blue = uint8(hue_to_rgb(p, q, hue - 1./3) * 255);
}
return result;
}
float
hsl_color::hue_to_rgb(float p, float q, float t)
{
if (t < 0)
t += 1;
if (t > 1)
t -= 1;
if (t < 1./6)
return p + (q - p) * 6 * t;
if (t < 1./2)
return q;
if (t < 2./3)
return p + (q - p) * (2./3 - t) * 6;
return p;
}
