1#define_import_path bevy_render::color_operations
2
3#import bevy_render::maths::FRAC_PI_3
4
5// Converts HSV to RGB.
6//
7// Input: H ∈ [0, 2π), S ∈ [0, 1], V ∈ [0, 1].
8// Output: R ∈ [0, 1], G ∈ [0, 1], B ∈ [0, 1].
9//
10// <https://en.wikipedia.org/wiki/HSL_and_HSV#HSV_to_RGB_alternative>
11fn hsv_to_rgb(hsv: vec3<f32>) -> vec3<f32> {
12    let n = vec3(5.0, 3.0, 1.0);
13    let k = (n + hsv.x / FRAC_PI_3) % 6.0;
14    return hsv.z - hsv.z * hsv.y * max(vec3(0.0), min(k, min(4.0 - k, vec3(1.0))));
15}
16
17// Converts RGB to HSV.
18//
19// Input: R ∈ [0, 1], G ∈ [0, 1], B ∈ [0, 1].
20// Output: H ∈ [0, 2π), S ∈ [0, 1], V ∈ [0, 1].
21//
22// <https://en.wikipedia.org/wiki/HSL_and_HSV#From_RGB>
23fn rgb_to_hsv(rgb: vec3<f32>) -> vec3<f32> {
24    let x_max = max(rgb.r, max(rgb.g, rgb.b));  // i.e. V
25    let x_min = min(rgb.r, min(rgb.g, rgb.b));
26    let c = x_max - x_min;  // chroma
27
28    var swizzle = vec3<f32>(0.0);
29    if (x_max == rgb.r) {
30        swizzle = vec3(rgb.gb, 0.0);
31    } else if (x_max == rgb.g) {
32        swizzle = vec3(rgb.br, 2.0);
33    } else {
34        swizzle = vec3(rgb.rg, 4.0);
35    }
36
37    let h = FRAC_PI_3 * (((swizzle.x - swizzle.y) / c + swizzle.z) % 6.0);
38
39    // Avoid division by zero.
40    var s = 0.0;
41    if (x_max > 0.0) {
42        s = c / x_max;
43    }
44
45    return vec3(h, s, x_max);
46}
47