PHP Colour Format Conversion

Allows the setting of getting of colour in various formats: RGB, HSL, CMY and CMYK.
The colour is stored as an RGB array. Since RGB to HSL and HSL to RGB conversion is quite heavy it might be better if you also stored the HSL value if it is going to be called frequently. However, I have a strong dislike of storing the same data in more than one place and since I will only do these conversions a couple of times .


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<?php
/**
 * pjlColour
 *
 * Set and return colours in different formats: RGB, HSL and css
 *
 * @package pjlColour
 *
 * @version 1.0
 * @copyright Peter Lux
 * @author Peter Lux
 * @link http://www.plux.co.uk/php-colour-format-conversion/
 * @license GPL http://www.opensource.org/licenses/gpl-license.html
 *
 * HSL format is Hue(0-360), Saturation (0-100), Luminance (0-100%)
 * RGB, CMY, CMYK have colour values of 0-255
 *
 *
 */


/**
 *  Set and return colours in different formats: RGB, HSL and css
 *
 */

class pjlColour {

    const RED = 0;
    const GREEN = 1;
    const BLUE = 2;

    const HUE = 0;
    const SATURATION = 1;
    const LUMINANCE = 2;

    protected $rgb = array(0,0,0);

    /**
    * Constructor.
    * @param int $r Red intensity 0 to 255.
    * @param int $g Green intensity 0 to 255.
    * @param int $b Blue intensity 0 to 255.
    *
    * @return void.
    */

    function __construct($r=0,$g=0,$b=0) {
        $this->rgb[self::RED] = $r;
        $this->rgb[self::GREEN] = $g;
        $this->rgb[self::BLUE] = $b;
    }

    /**
    * setRGB.
    *
    * sets the colour using RGB values
    *
    * @param int $r Red intensity 0 to 255.
    * @param int $g Green intensity 0 to 255.
    * @param int $b Blue intensity 0 to 255.
    *
    * @return void.
    */

    function setRGB($r,$g,$b) {
        $this->rgb[self::RED] = $r;
        $this->rgb[self::GREEN] = $g;
        $this->rgb[self::BLUE] = $b;
    }
    /**
    * getRGB.
    *
    * @return array (red, green, blue).
    */

    function getRGB() {
        return ($this->rgb);
    }

    /**
    * getHexDigit($hex).
    * @param int $hex digit to convert.
    *
    * @return string the hexidecimal representation of the digit with leading zero.
    */

    private function getHexDigit($hex) {
        $hexDigit = dechex($hex);

        // Add a leading zero if necessary
        if(strlen($hexDigit) == 1) {
            $hexDigit = "0" . $hexDigit;
        }
        return $hexDigit;
    }


    /**
    * setHex($hex).
    * @param int $hex string in css hexidecimal with leading #.
    *
    * @return true.
    */

    public function setHex($hex) {
        if (substr($hex,0,1) != '#')
            throw new Exception ('"'.$hex.'" is not a valid hex colour');
        $hex = substr($hex,1);

        $d = '[a-fA-F0-9]';

        // Make sure $hex is valid
        if (preg_match("/^($d$d)($d$d)($d$d)\$/", $hex, $rgb)) {
            $this->rgb[self::RED] = hexdec($rgb[1]);
            $this->rgb[self::GREEN] = hexdec($rgb[2]);
            $this->rgb[self::BLUE] = hexdec($rgb[3]);
        } else if (preg_match("/^($d)($d)($d)$/", $hex, $rgb)) {
            $this->rgb[self::RED] = hexdec($rgb[1] . $rgb[1]);
            $this->rgb[self::GREEN] = hexdec($rgb[2] . $rgb[2]);
            $this->rgb[self::BLUE] = hexdec($rgb[3] . $rgb[3]);
        } else {
            throw new Exception ("cannot convert hex '$hex' to RGB");
        }
        return(true);
    }

    /**
    * getHex().
    * @param void.
    *
    * @return string current colour in css hexidecimal notation.
    */

    function getHex() {
        return '#'.$this->getHexDigit($this->rgb[self::RED]).$this->getHexDigit($this->rgb[self::GREEN]).$this->getHexDigit($this->rgb[self::BLUE]);
    }

    /**
    * getHSL().
    * @param void.
    *
    * @return array(hue, saturation, Luminance).
    *
    * algorithum based on
    * http://www.niwa.nu/2013/05/math-behind-colorspace-conversions-rgb-hsl/
    *
    */

    function getHSL() {
        $Saturation = 0;
        $Luminance = 0;
        $Hue = 0;

        $r = $this->rgb[self::RED]/255;
        $g = $this->rgb[self::GREEN]/255;
        $b = $this->rgb[self::BLUE]/255;

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

        $Luminance = ($min + $max)/2;
        if ($min != $max) {
            if ($Luminance < 0.5) {
                $Saturation = ($max-$min)/($max+$min);
            } else {
                $Saturation = ( $max-$min)/(2.0-$max-$min);
            }
            if ($max == $r) {
                $Hue = ($g-$b)/($max-$min);
            } else if ($max == $g) {
                $Hue = 2.0 + ($b-$r)/($max-$min);
            } else {
                $Hue = 4.0 + ($r-$g)/($max-$min);
            }
        }
        $Hue = $Hue * 60;
        if ($Hue < 0) {
            $Hue = $Hue + 360;
        }

        return(array(round($Hue,2),round($Saturation*100,2),round($Luminance*100,2)));
    }

    /**
    * setHSL($h,$s,$l).
    * @param float Hue 0-360.
    * @param float Saturation 0 - 100%
    * @param float Luminance 0 - 100%
    *
    * @return void.
    *
    * algorithum based on
    * http://www.niwa.nu/2013/05/math-behind-colorspace-conversions-rgb-hsl/
    *
    */

    function setHSL($h,$s,$l) {
        // convert values to fractions
        $h = $h /360;
        $s = $s / 100;
        $l = $l / 100;


        // if there is no saturation then it is greyscale
        if ($s == 0) {
            $this->rgb[self::RED] = $l * 255;
            $this->rgb[self::GREEN] = $this->rgb[self::RED];
            $this->rgb[self::BLUE] = $this->rgb[self::RED];
        } else {
            if ($l < 0.5) {
                $temporary_1 = $l * (1 + $s);
            } else {
                $temporary_1 = $l + $s - $l * $s;
            }

            $temporary_2 = 2 * $l - $temporary_1;

            // $temporary is $h + 0.333 for red, $h for green and $h - 0.333 for blue. Therefore I multiply
            // 0.333 by (1-$i) which is 1,0,-1
            for ($i=0 ; $i<3 ; $i++) {
                $temporary = $h + (1-$i)*0.333;
                if ($temporary > 1)
                    $temporary = $temporary - 1;
                else if ($temporary < 0 )
                    $temporary += 1;

                if (6 * $temporary < 1) {
                    $this->rgb[$i] = intval(($temporary_2 + ($temporary_1 - $temporary_2) * 6 * $temporary) * 255);
                } else if (2 * $temporary < 1) {
                    $this->rgb[$i] = intval($temporary_1 * 255);
                } else if (3 * $temporary < 2) {
                    $this->rgb[$i] = intval(($temporary_2 + ($temporary_1 - $temporary_2) * (0.666 - $temporary) * 6) * 255);
                } else {
                    $this->rgb[$i] = intval($temporary_2 * 255);
                }
            }
        }
    }

    /**
    * function setCMY($c,$m,$y).
    * @param int cyan intensity (0-255)
    * @param int Magenta intensity (0-255)
    * @param int Yellow intensity (0-255)
    *
    * @return void.
    *
    */

    public function setCMY($c, $m, $y) {
        setRGB(255-$c, 255-$m, 255-$y);
    }

    /**
    * getCMY().
    * @param void.
    *
    * @return array(cyan, magenta, yellow).
    *
    */

    public function getCMY() {
        return(array(255-$this->rgb[self::RED],255-$this->rgb[self::GREEN],255-$this->rgb[self::BLUE]));
    }

    /**
    * function setCMYK($c,$m,$y).
    * @param int cyan intensity (0-255)
    * @param int Magenta intensity (0-255)
    * @param int Yellow intensity (0-255)
    *
    * @return void.
    *
    */

    public function setCMYK($c, $m, $y, $k) {
        setRGB((255-$c)*(255-$k), (255-$m)*(255-$k), (255-$y)*(255-$k));
    }

    /**
    * getCMYK().
    * @param void.
    *
    * @return array(cyan, magenta, yellow).
    *
    */

    public function getCMYK() {
        $k = 255 - max($this->rgb);
        return(array(round(255*((255-$this->rgb[self::RED]-$k)/(255-$k)),0),
                     round(255*((255-$this->rgb[self::GREEN]-$k)/(255-$k)),0),
                     round(255*((255-$this->rgb[self::BLUE]-$k)/(255-$k)),0),
                     $k));
    }

    /**
    * function increaseLuminance($increase).
    * @param float % increase in Luminance (use negative $increase to decrease).
    *
    * @return void.
    *
    * if luminance is not in range 0-100 it corrects to 0 or 100
    */

    public function increaseLuminance($increase) {
        $hsl = $this->getHSL();
        $l = $hsl[2] + $increase;
        if ($l > 100) $l = 100;
        if ($l < 0) $l = 0;
        $this->setHSL($hsl[self::HUE], $hsl[self::SATURATION], $l);
    }

    /**
    * function increaseSaturation($increase).
    * @param float % increase in Saturation (use negative $increase to decrease).
    *
    * @return void.
    *
    * if saturation is not in range 0-100 it corrects to 0 or 100
    */

    public function increaseSaturation($increase) {
        $hsl = $this->getHSL();
        $s = $hsl[1] + $increase;
        if ($s > 100) $s = 100;
        if ($s < 0) $s = 0;
        $this->setHSL($hsl[self::HUE], $s, $hsl[self::LUMINANCE]);
    }

    /**
    * function increaseSaturation($increase).
    * @param float degree increase in Hue (use negative $increase to decrease).
    *
    * @return void.
    *
    * Will wrap round if $hue is out of 0-360 range
    * this can be used to set complimenary colour by calling ->increaseHue(180)
    */

    public function increaseHue($increase) {
        $increase = $increase % 360;
        $hsl = $this->getHSL();
        $h = $hsl[self::HUE] + $increase;
        if ($h > 360) $h = $h - 360;
        if ($h < 0) $h = $h + 360;
        $this->setHSL($h, $hsl[self::SATURATION], $hsl[self::LUMINANCE]);
    }
}
?>

Example of use:

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$colour = new pjlColour(140,80,120); // create new colour with R,G,B values
$colour->getHex();  // get hex value i.e. #8c5078
$colour->getHSL();  // returns an array containing HSL values (0-360, 0-100, 0-100)
$colour->getCMY();  // returns an array of the CMY values (0-255)
$colour->getCMYK(); // returns an array of the CMYK values (0-255)
$colour->setHSL(200,50,50); // set HSL value hue:200 with 50% saturation and luminance
$colour->setCMYK(0,127,127,50); // set CMYK values
$colour2 = clone $colour;  // get a copy of the colour
$colour2->increaseHue(180); // increase Hue by 180 degrees - wraps round after 360
$colour2->increaseSaturation(10) // increase the saturation by 10%
$colour2->increaseLuminance(-20) // decrease the Luminance by 20%
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