hsl.c

#include <stdlib.h>
#include <stdio.h>
#include <stdint.h>
#include <math.h>

#define RGB(r,g,b) (((r) & 0xFF) | (((g) & 0xFF) << 8) | (((b) & 0xFF) << 16))
#define RED(rgb) ((rgb) & 0xFF)
#define GRN(rgb) (((rgb) >> 8) & 0xFF)
#define BLU(rgb) (((rgb) >> 16) & 0xFF)

uint32_t rgb_from_hsl(float hue, float sat, float lig)
{
    float C = (1.0f - fabsf(2.0f * lig - 1.0f)) * sat; // chroma
    float H = hue / 60.0f;
    float X = C * (1.0f - fabsf(fmodf(H, 2.0f) - 1));
    float R,G,B;
    switch ((int)H) {
        default:
        case 0: R=C, G=X, B=0; break;
        case 1: R=X, G=C, B=0; break;
        case 2: R=0, G=C, B=X; break;
        case 3: R=0, G=X, B=C; break;
        case 4: R=X, G=0, B=C; break;
        case 5: R=C, G=0, B=X; break;
    }
    float m = lig - C/2.0f;
    int r = (R+m) * 255.0f;
    int g = (G+m) * 255.0f;
    int b = (B+m) * 255.0f;
    return RGB(r, g, b);
}

int main()
{
    uint32_t rgb = rgb_from_hsl(260, 1.0, 0.6);
    printf("%u, %u, %u\n", RED(rgb), GRN(rgb), BLU(rgb));
}