HSV test

gistfile1.txt

$ g++ -std=c++17 -o hsv hsv.cpp
$ ./hsv 2,100,59
brightness=0, rgb=0,0,0
input=2,100,59
_setRGBInputValue(255,8,0)
brightness=150, rgb=255,8,0

hsv.cpp

#include <cmath>
#include <algorithm>
#include <string>
#include <iostream>

constexpr unsigned char LIGHT_MIN_VALUE = 0;
constexpr unsigned char LIGHT_MAX_VALUE = 255;

unsigned char red = 0;
unsigned char green = 0;
unsigned char blue = 0;
unsigned char _light_brightness = 0;

void dump() {
    std::cout
        << "brightness="<< int(_light_brightness)
        << ", " << "rgb="
        << int(std::clamp(red, LIGHT_MIN_VALUE, LIGHT_MAX_VALUE))
        << "," << int(std::clamp(green, LIGHT_MIN_VALUE, LIGHT_MAX_VALUE))
        << "," << int(std::clamp(blue, LIGHT_MIN_VALUE, LIGHT_MAX_VALUE))
        << std::endl;
}

void _setRGBInputValue(unsigned char _red, unsigned char _green, unsigned char _blue) {
    red = _red; green = _green; blue = _blue;
    std::cout << "_setRGBInputValue(";
    std::cout << int(std::clamp(red, LIGHT_MIN_VALUE, LIGHT_MAX_VALUE)) << ",";
    std::cout << int(std::clamp(green, LIGHT_MIN_VALUE, LIGHT_MAX_VALUE)) << ",";
    std::cout << int(std::clamp(blue, LIGHT_MIN_VALUE, LIGHT_MAX_VALUE));
    std::cout << ")" << std::endl;
}

void _fromHSV(const char * hsv) {

    std::string str(hsv);
    std::cout << "input=" << str << std::endl;

    if (!str.length()) return;

    unsigned char value[3] = {0,0,0};
    unsigned char idx = 0;
    unsigned char pos = 0;
    do {
        if (!str.length()) break;
        pos = str.find(',');
        if (pos == std::string::npos) break;
        value[idx++] = std::stoi(str.substr(0, pos));
        str.erase(0, pos + 1);
    } while(pos != std::string::npos);

    if (idx != 3) return;

    // HSV to RGB transformation -----------------------------------------------

    //INPUT: [0,100,57]
    //IS: [145,0,0]
    //SHOULD: [255,0,0]

    double h = (value[0] == 360) ? 0 : (double) value[0] / 60.0;
    double f = (h - std::floor(h));
    double s = (double) value[1] / 100.0;

    _light_brightness = std::round((double) value[2] * 2.55); // (255/100)
    unsigned char p = std::lround(255 * (1.0 - s));
    unsigned char q = std::lround(255 * (1.0 - s * f));
    unsigned char t = std::lround(255 * (1.0 - s * (1.0 - f)));

    switch (int(h)) {
        case 0:
            _setRGBInputValue(255, t, p);
            break;
        case 1:
            _setRGBInputValue(q, 255, p);
            break;
        case 2:
            _setRGBInputValue(p, 255, t);
            break;
        case 3:
            _setRGBInputValue(p, q, 255);
            break;
        case 4:
            _setRGBInputValue(t, p, 255);
            break;
        case 5:
            _setRGBInputValue(255, p, q);
            break;
        default:
            _setRGBInputValue(0, 0, 0);
            break;
    }
}

int main(int argc, char** argv) {
    if (argc != 2) {
        std::cout << "[prog] [h,s,v string]" << std::endl;
        std::terminate();
    }
    dump();
    _fromHSV(argv[1]);
    dump();
}