Momentum-Firmware/lib/toolbox/colors.c

// https://stackoverflow.com/a/14733008

#include "colors.h"

inline int rgbcmp(const RgbColor* a, const RgbColor* b) {
    return memcmp(a, b, sizeof(RgbColor));
}

inline int hsvcmp(const HsvColor* a, const HsvColor* b) {
    return memcmp(a, b, sizeof(HsvColor));
}

RgbColor hsv2rgb(HsvColor hsv) {
    RgbColor rgb;
    uint8_t region, remainder, p, q, t;

    if(hsv.s == 0) {
        rgb.r = hsv.v;
        rgb.g = hsv.v;
        rgb.b = hsv.v;
        return rgb;
    }

    region = hsv.h / 43;
    remainder = (hsv.h - (region * 43)) * 6;

    p = (hsv.v * (255 - hsv.s)) >> 8;
    q = (hsv.v * (255 - ((hsv.s * remainder) >> 8))) >> 8;
    t = (hsv.v * (255 - ((hsv.s * (255 - remainder)) >> 8))) >> 8;

    switch(region) {
    case 0:
        rgb.r = hsv.v;
        rgb.g = t;
        rgb.b = p;
        break;
    case 1:
        rgb.r = q;
        rgb.g = hsv.v;
        rgb.b = p;
        break;
    case 2:
        rgb.r = p;
        rgb.g = hsv.v;
        rgb.b = t;
        break;
    case 3:
        rgb.r = p;
        rgb.g = q;
        rgb.b = hsv.v;
        break;
    case 4:
        rgb.r = t;
        rgb.g = p;
        rgb.b = hsv.v;
        break;
    default:
        rgb.r = hsv.v;
        rgb.g = p;
        rgb.b = q;
        break;
    }

    return rgb;
}

HsvColor rgb2hsv(RgbColor rgb) {
    HsvColor hsv;
    uint8_t rgbMin, rgbMax;

    rgbMin = rgb.r < rgb.g ? (rgb.r < rgb.b ? rgb.r : rgb.b) : (rgb.g < rgb.b ? rgb.g : rgb.b);
    rgbMax = rgb.r > rgb.g ? (rgb.r > rgb.b ? rgb.r : rgb.b) : (rgb.g > rgb.b ? rgb.g : rgb.b);

    hsv.v = rgbMax;
    if(hsv.v == 0) {
        hsv.h = 0;
        hsv.s = 0;
        return hsv;
    }

    hsv.s = 255 * ((long)rgbMax - (long)rgbMin) / hsv.v;
    if(hsv.s == 0) {
        hsv.h = 0;
        return hsv;
    }

    if(rgbMax == rgb.r)
        hsv.h = 0 + 43 * (rgb.g - rgb.b) / (rgbMax - rgbMin);
    else if(rgbMax == rgb.g)
        hsv.h = 85 + 43 * (rgb.b - rgb.r) / (rgbMax - rgbMin);
    else
        hsv.h = 171 + 43 * (rgb.r - rgb.g) / (rgbMax - rgbMin);

    return hsv;
}