index/src/Colour/ColourHSL.php

<?php
namespace Index\Colour;

class ColourHSL extends Colour {
    private float $hue;
    private float $saturation;
    private float $lightness;
    private float $alpha;

    private int $red;
    private int $green;
    private int $blue;

    public function __construct(float $hue, float $saturation, float $lightness, float $alpha) {
        $hue %= 360;

        $this->hue = $hue;
        $this->saturation = max(0.0, min(1.0, $saturation));
        $this->lightness = max(0.0, min(1.0, $lightness));
        $this->alpha = max(0.0, min(1.0, $alpha));

        $c = (1 - abs(2 * $lightness - 1)) * $saturation;
        $x = $c * (1 - abs(fmod($hue / 60, 2) - 1));
        $m = $lightness - ($c / 2);

        $r = $g = $b = 0;

        if($hue < 60) {
            $r = $c;
            $g = $x;
        } elseif($hue < 120) {
            $r = $x;
            $g = $c;
        } elseif($hue < 180) {
            $g = $c;
            $b = $x;
        } elseif($hue < 240) {
            $g = $x;
            $b = $c;
        } elseif($hue < 300) {
            $r = $x;
            $b = $c;
        } else {
            $r = $c;
            $b = $x;
        }

        $this->red = (int)round(($r + $m) * 255);
        $this->green = (int)round(($g + $m) * 255);
        $this->blue = (int)round(($b + $m) * 255);
    }

    public function getRed(): int {
        return $this->red;
    }

    public function getGreen(): int {
        return $this->green;
    }

    public function getBlue(): int {
        return $this->blue;
    }

    public function getHue(): float {
        return $this->hue;
    }

    public function getSaturation(): float {
        return $this->saturation;
    }

    public function getLightness(): float {
        return $this->lightness;
    }

    public function getAlpha(): float {
        return $this->alpha;
    }

    public function shouldInherit(): bool {
        return false;
    }

    public function __toString(): string {
        if($this->alpha < 1.0)
            return sprintf('hsla(%.2Fdeg, %d%%, %d%%, %.3F)', $this->hue, $this->saturation * 100, $this->lightness * 100, $this->alpha);
        return sprintf('hsl(%.2Fdeg, %d%%, %d%%)', $this->hue, $this->saturation * 100, $this->lightness * 100);
    }

    public static function convert(Colour $colour): ColourHSL {
        if($colour instanceof ColourHSL)
            return $colour;

        $r = $colour->getRed() / 255.0;
        $g = $colour->getGreen() / 255.0;
        $b = $colour->getBlue() / 255.0;

        $max = max($r, $g, $b);
        $min = min($r, $g, $b);

        $h = $s = 0;
        $l = ($max + $min) / 2;
        $d = $max - $min;

        if($d <> 0) {
            $s = $d / (1 - abs(2 * $l - 1));

            if($max == $r) {
                $h = 60 * fmod((($g - $b) / $d), 6);
                if($b > $g)
                    $h += 360;
            } elseif($max == $g) {
                $h = 60 * (($b - $r) / $d + 2);
            } else {
                $h = 60 * (($r - $g) / $d + 4);
            }
        }

        return new ColourHSL(
            round($h, 3),
            round($s, 3),
            round($l, 3),
            $colour->getAlpha()
        );
    }
}