libscscreensaver/Color.cpp

//
// Color.cpp
// screensaver
//
// Created by Bob Polis at 2020-10-27
// Copyright (c) 2020 SwiftCoder. All rights reserved.
//

#include "Color.hpp"
#include <algorithm>
#include <cmath>

Color::Color(const RGB& rgb) : _rgb {rgb} {}

Color::Color(const HSB& hsb) {
    if (hsb.s <= 0) {
        _rgb.r = _rgb.g = _rgb.b = hsb.b;
    } else {
        double hi = hsb.h / 60;
        int i = static_cast<int>(hi);
        double f = hi - i;
        double p = hsb.b * (1.0 - hsb.s);
        double q = hsb.b * (1.0 - (hsb.s * f));
        double t = hsb.b * (1.0 - (hsb.s * (1.0 -f)));
        switch (i) {
            case 0:
                _rgb.r = hsb.b;
                _rgb.g = t;
                _rgb.b = p;
                break;
            case 1:
                _rgb.r = q;
                _rgb.g = hsb.b;
                _rgb.b = p;
                break;
            case 2:
                _rgb.r = p;
                _rgb.g = hsb.b;
                _rgb.b = t;
                break;
            case 3:
                _rgb.r = p;
                _rgb.g = q;
                _rgb.b = hsb.b;
                break;
            case 4:
                _rgb.r = t;
                _rgb.g = p;
                _rgb.b = hsb.b;
                break;
            case 5:
            default:
                _rgb.r = hsb.b;
                _rgb.g = p;
                _rgb.b = q;
                break;
        }
    }
}

Color::operator HSB() const {
    HSB hsb;
    double rgb_max = std::max<double>({_rgb.r, _rgb.g, _rgb.b});
    double rgb_min = std::min<double>({_rgb.r, _rgb.g, _rgb.b});
    double delta = rgb_max - rgb_min;
    if (delta < 0.00001) {
        hsb.h = 0;
        hsb.s = 0;
        hsb.b = rgb_max;
        return hsb;
    }
    if (_rgb.r >= rgb_max) { // between yellow and magenta
        hsb.h = (_rgb.g - _rgb.b) / delta;
    } else if (_rgb.g >= rgb_max) { //  between cyan and yellow
        hsb.h = 2.0 + (_rgb.b - _rgb.r) / delta;
    } else { // between magenta and cyan
        hsb.h = 4.0 + (_rgb.r - _rgb.g) / delta;
    }
    hsb.h *= 60;
    hsb.s = rgb_max > 0.0 ? delta / rgb_max : 0;
    hsb.b = rgb_max;
    return hsb;
}