srctree

#include <algorithm>

#include <cmath>

// NOLINTNEXTLINE(bugprone-easily-swappable-parameters)

static Color from_hsl(float hue, float saturation, float light) { return from_hsla(hue, saturation, light, 1.f); }

// NOLINTNEXTLINE(bugprone-easily-swappable-parameters)

static Color from_hsla(float hue, float saturation, float light, float alpha) {

// https://www.w3.org/TR/css-color-3/#hsl-color

hue = std::fmod(hue, 360.f);

if (hue < 0.f) {

hue += 360.f;

}

 

saturation = std::clamp(saturation, 0.f, 1.f);

light = std::clamp(light, 0.f, 1.f);

alpha = std::clamp(alpha, 0.f, 1.f);

 

auto hue_to_rgb = [&](int n) {

float k = std::fmod(n + hue / 30.f, 12.f);

float aa = saturation * std::min(light, 1.f - light);

return light - aa * std::clamp(std::min(k - 3.f, 9.f - k), -1.f, 1.f);

};

 

return {

.r = static_cast<std::uint8_t>(std::lround(255 * hue_to_rgb(0))),

.g = static_cast<std::uint8_t>(std::lround(255 * hue_to_rgb(8))),

.b = static_cast<std::uint8_t>(std::lround(255 * hue_to_rgb(4))),

.a = static_cast<std::uint8_t>(std::lround(255 * alpha)),

};

}

 

// Some of the HSL test-cases are from or inspired by

// https://github.com/web-platform-tests/wpt/blob/0bbb3104a8bc5381d3974adf4535fa0dfe191060/css/css-color/parsing/color-computed-hsl.html

etest::test("Color::from_hsl", [] {

expect_eq(Color::from_hsl(120.f, 1.f, 0.25f), Color{.g = 0x80});

 

expect_eq(Color::from_hsl(120.f, .3f, .5f), Color{89, 166, 89});

expect_eq(Color::from_hsl(0.f, 0.f, 0.f), Color{0, 0, 0});

expect_eq(Color::from_hsl(0.f, 1.f, .5f), Color{255, 0, 0});

expect_eq(Color::from_hsl(120.f, 0.f, 0.f), Color{0, 0, 0});

expect_eq(Color::from_hsl(120.f, 0.f, .5f), Color{128, 128, 128});

expect_eq(Color::from_hsl(120.f, 1.f, .5f), Color{0, 255, 0});

expect_eq(Color::from_hsl(120.f, .3f, .5f), Color{89, 166, 89});

expect_eq(Color::from_hsl(120.f, .8f, 0), Color{0, 0, 0});

 

expect_eq(Color::from_hsl(300.f, .5f, .5f), Color{191, 64, 191});

expect_eq(Color::from_hsl(60.f, 1.00f, .375f), Color{191, 191, 0});

expect_eq(Color::from_hsl(30.f, 1.f, 1.f), Color{255, 255, 255});

 

// Angles are represented as a part of a circle and wrap around.

expect_eq(Color::from_hsl(-300.f, 1.f, .375f), Color{191, 191, 0});

expect_eq(Color::from_hsl(780.f, 1.f, .375f), Color{191, 191, 0});

});

 

etest::test("Color::from_hsl/a", [] {

expect_eq(Color::from_hsla(0.f, 0.f, 0.f, 0.f), Color{0, 0, 0, 0});

expect_eq(Color::from_hsla(0.f, 0.f, 0.f, 0.5f), Color{0, 0, 0, 128});

expect_eq(Color::from_hsla(120.f, .3f, .5f, .5f), Color{89, 166, 89, 128});

expect_eq(Color::from_hsla(30.f, 1.f, 1.f, 1.f), Color{255, 255, 255});

 

// Angles are represented as a part of a circle and wrap around.

// Invalid alpha values should be clamped to 0 and 1 respectively

expect_eq(Color::from_hsla(-300.f, 1.f, .375f, -3.f), Color{191, 191, 0, 0});

expect_eq(Color::from_hsla(-300.f, 1.f, .375f, 0.f), Color{191, 191, 0, 0});

expect_eq(Color::from_hsla(-300.f, 1.f, .375f, .2f), Color{191, 191, 0, 51});

expect_eq(Color::from_hsla(-300.f, 1.f, .375f, 1.f), Color{191, 191, 0});

expect_eq(Color::from_hsla(-300.f, 1.f, .375f, 12.f), Color{191, 191, 0});

});