✏️ Editing: class.color.php Writable

<?php // phpcs:ignore WordPress.Files.FileName.InvalidClassFileName
/**
 * Color utility and conversion
 *
 * Represents a color value, and converts between RGB/HSV/XYZ/Lab/HSL
 *
 * Example:
 * $color = new Jetpack_Color(0xFFFFFF);
 *
 * @author Harold Asbridge <hasbridge@gmail.com>
 * @author Matt Wiebe <wiebe@automattic.com>
 * @license https://www.opensource.org/licenses/MIT
 *
 * @package automattic/jetpack
 */

// phpcs:disable WordPress.NamingConventions.ValidFunctionName.MethodNameInvalid

if ( ! class_exists( 'Jetpack_Color' ) ) {
	/**
	 * Color utilities
	 */
	class Jetpack_Color {
		/**
		 * Color code (later array or string, depending on type)
		 *
		 * @var int|array|string
		 */
		protected $color = 0;

/**
		 * Initialize object
		 *
		 * @param string|array $color A color of the type $type.
		 * @param string       $type The type of color we will construct from.
		 *        One of hex (default), rgb, hsl, int.
		 */
		public function __construct( $color = null, $type = 'hex' ) {
			_deprecated_function( 'Jetpack_Color::__construct', 'jetpack-13.8' );

if ( $color ) {
				switch ( $type ) {
					case 'hex':
						$this->fromHex( $color );
						break;
					case 'rgb':
						if ( is_array( $color ) && count( $color ) === 3 ) {
							list( $r, $g, $b ) = array_values( $color );
							$this->fromRgbInt( $r, $g, $b );
						}
						break;
					case 'hsl':
						if ( is_array( $color ) && count( $color ) === 3 ) {
							list( $h, $s, $l ) = array_values( $color );
							$this->fromHsl( $h, $s, $l );
						}
						break;
					case 'int':
						$this->fromInt( $color );
						break;
					default:
						// there is no default.
						break;
				}
			}
		}

/**
		 * Init color from hex value
		 *
		 * @param string $hex_value Color hex value.
		 *
		 * @return $this
		 * @throws RangeException Invalid color code range error.
		 */
		public function fromHex( $hex_value ) {
			$hex_value = str_replace( '#', '', $hex_value );
			// handle short hex codes like #fff.
			if ( 3 === strlen( $hex_value ) ) {
				$hex_value = $hex_value[0] . $hex_value[0] . $hex_value[1] . $hex_value[1] . $hex_value[2] . $hex_value[2];
			}
			return $this->fromInt( hexdec( $hex_value ) );
		}

/**
		 * Init color from integer RGB values
		 *
		 * @param int $red   Red color code.
		 * @param int $green Green color code.
		 * @param int $blue  Blue color code.
		 *
		 * @return $this
		 * @throws RangeException Invalid color code range error.
		 */
		public function fromRgbInt( $red, $green, $blue ) {
			if ( $red < 0 || $red > 255 ) {
				throw new RangeException( 'Red value ' . $red . ' out of valid color code range' );
			}

if ( $green < 0 || $green > 255 ) {
				throw new RangeException( 'Green value ' . $green . ' out of valid color code range' );
			}

if ( $blue < 0 || $blue > 255 ) {
				throw new RangeException( 'Blue value ' . $blue . ' out of valid color code range' );
			}

$this->color = ( intval( $red ) << 16 ) + ( intval( $green ) << 8 ) + intval( $blue );

return $this;
		}

/**
		 * Init color from hex RGB values
		 *
		 * @param string $red   Red color code.
		 * @param string $green Green color code.
		 * @param string $blue  Blue color code.
		 *
		 * @return $this
		 */
		public function fromRgbHex( $red, $green, $blue ) {
			return $this->fromRgbInt( hexdec( $red ), hexdec( $green ), hexdec( $blue ) );
		}

/**
		 * Converts an HSL color value to RGB. Conversion formula
		 * adapted from https://en.wikipedia.org/wiki/HSL_color_space.
		 *
		 * @param  int $h Hue. [0-360].
		 * @param  int $s Saturation [0, 100].
		 * @param  int $l Lightness [0, 100].
		 */
		public function fromHsl( $h, $s, $l ) {
			$h /= 360;
			$s /= 100;
			$l /= 100;

if ( 0 === $s ) {
				// achromatic.
				$r = $l;
				$g = $l;
				$b = $l;
			} else {
				$q = $l < 0.5 ? $l * ( 1 + $s ) : $l + $s - $l * $s;
				$p = 2 * $l - $q;
				$r = $this->hue2rgb( $p, $q, $h + 1 / 3 );
				$g = $this->hue2rgb( $p, $q, $h );
				$b = $this->hue2rgb( $p, $q, $h - 1 / 3 );
			}

return $this->fromRgbInt( $r * 255, $g * 255, $b * 255 );
		}

/**
		 * Helper function for Jetpack_Color::fromHsl()
		 *
		 * @param  float $p Minimum of R/G/B [0, 1].
		 * @param  float $q Maximum of R/G/B [0, 1].
		 * @param  float $t Adjusted hue [0, 1].
		 */
		private function hue2rgb( $p, $q, $t ) {
			if ( $t < 0 ) {
				++$t;
			}
			if ( $t > 1 ) {
				--$t;
			}
			if ( $t < 1 / 6 ) {
				return $p + ( $q - $p ) * 6 * $t;
			}
			if ( $t < 1 / 2 ) {
				return $q;
			}
			if ( $t < 2 / 3 ) {
				return $p + ( $q - $p ) * ( 2 / 3 - $t ) * 6;
			}
			return $p;
		}

/**
		 * Init color from integer value
		 *
		 * @param int $int_value Color code.
		 *
		 * @return $this
		 * @throws RangeException Invalid color code range error.
		 */
		public function fromInt( $int_value ) {
			if ( $int_value < 0 || $int_value > 16777215 ) {
				throw new RangeException( $int_value . ' out of valid color code range' );
			}

$this->color = $int_value;

return $this;
		}

/**
		 * Convert color to hex
		 *
		 * @return string
		 */
		public function toHex() {
			return sprintf( '%06x', $this->color );
		}

/**
		 * Convert color to RGB array (integer values)
		 *
		 * @return array
		 */
		public function toRgbInt() {
			return array(
				'red'   => (int) ( 255 & ( $this->color >> 16 ) ),
				'green' => (int) ( 255 & ( $this->color >> 8 ) ),
				'blue'  => (int) ( 255 & ( $this->color ) ),
			);
		}

/**
		 * Convert color to RGB array (hex values)
		 *
		 * @return array
		 */
		public function toRgbHex() {
			$r = array();
			foreach ( $this->toRgbInt() as $item ) {
				$r[] = dechex( $item );
			}
			return $r;
		}

/**
		 * Get Hue/Saturation/Value for the current color
		 * (float values, slow but accurate)
		 *
		 * @return array
		 */
		public function toHsvFloat() {
			$rgb = $this->toRgbInt();

$rgb_min = min( $rgb );
			$rgb_max = max( $rgb );

$hsv = array(
				'hue' => 0,
				'sat' => 0,
				'val' => $rgb_max,
			);

// If v is 0, color is black.
			if ( 0 === $hsv['val'] ) {
				return $hsv;
			}

// Normalize RGB values to 1.
			$rgb['red']   /= $hsv['val'];
			$rgb['green'] /= $hsv['val'];
			$rgb['blue']  /= $hsv['val'];
			$rgb_min       = min( $rgb );
			$rgb_max       = max( $rgb );

// Calculate saturation.
			$hsv['sat'] = $rgb_max - $rgb_min;
			if ( 0 === $hsv['sat'] ) {
				$hsv['hue'] = 0;
				return $hsv;
			}

// Normalize saturation to 1.
			$rgb['red']   = ( $rgb['red'] - $rgb_min ) / ( $rgb_max - $rgb_min );
			$rgb['green'] = ( $rgb['green'] - $rgb_min ) / ( $rgb_max - $rgb_min );
			$rgb['blue']  = ( $rgb['blue'] - $rgb_min ) / ( $rgb_max - $rgb_min );
			$rgb_min      = min( $rgb );
			$rgb_max      = max( $rgb );

// Calculate hue.
			if ( $rgb_max === $rgb['red'] ) {
				$hsv['hue'] = 0.0 + 60 * ( $rgb['green'] - $rgb['blue'] );
				if ( $hsv['hue'] < 0 ) {
					$hsv['hue'] += 360;
				}
			} elseif ( $rgb_max === $rgb['green'] ) {
				$hsv['hue'] = 120 + ( 60 * ( $rgb['blue'] - $rgb['red'] ) );
			} else {
				$hsv['hue'] = 240 + ( 60 * ( $rgb['red'] - $rgb['green'] ) );
			}

return $hsv;
		}

/**
		 * Get HSV values for color
		 * (integer values from 0-255, fast but less accurate)
		 *
		 * @return array
		 */
		public function toHsvInt() {
			$rgb = $this->toRgbInt();

$rgb_min = min( $rgb );
			$rgb_max = max( $rgb );

$hsv = array(
				'hue' => 0,
				'sat' => 0,
				'val' => $rgb_max,
			);

// If value is 0, color is black.
			if ( 0 === $hsv['val'] ) {
				return $hsv;
			}

// Calculate saturation.
			$hsv['sat'] = round( 255 * ( $rgb_max - $rgb_min ) / $hsv['val'] );
			if ( 0 === $hsv['sat'] ) {
				$hsv['hue'] = 0;
				return $hsv;
			}

// Calculate hue.
			if ( $rgb_max === $rgb['red'] ) {
				$hsv['hue'] = round( 0 + 43 * ( $rgb['green'] - $rgb['blue'] ) / ( $rgb_max - $rgb_min ) );
			} elseif ( $rgb_max === $rgb['green'] ) {
				$hsv['hue'] = round( 85 + 43 * ( $rgb['blue'] - $rgb['red'] ) / ( $rgb_max - $rgb_min ) );
			} else {
				$hsv['hue'] = round( 171 + 43 * ( $rgb['red'] - $rgb['green'] ) / ( $rgb_max - $rgb_min ) );
			}
			if ( $hsv['hue'] < 0 ) {
				$hsv['hue'] += 255;
			}

return $hsv;
		}

/**
		 * Converts an RGB color value to HSL. Conversion formula
		 * adapted from https://en.wikipedia.org/wiki/HSL_color_space.
		 * Assumes r, g, and b are contained in the set [0, 255] and
		 * returns h in [0, 360], s in [0, 100], l in [0, 100]
		 *
		 * @return  Array          The HSL representation
		 */
		public function toHsl() {
			list( $r, $g, $b ) = array_values( $this->toRgbInt() );
			$r                /= 255;
			$g                /= 255;
			$b                /= 255;
			$max               = max( $r, $g, $b );
			$min               = min( $r, $g, $b );
			$l                 = ( $max + $min ) / 2;

if ( $max === $min ) {
				// achromatic.
				$s = 0;
				$h = 0;
			} else {
				$d = $max - $min;
				$s = $l > 0.5 ? $d / ( 2 - $max - $min ) : $d / ( $max + $min );
				switch ( $max ) {
					case $r:
						$h = ( $g - $b ) / $d + ( $g < $b ? 6 : 0 );
						break;
					case $g:
						$h = ( $b - $r ) / $d + 2;
						break;
					case $b:
						$h = ( $r - $g ) / $d + 4;
						break;
				}
				$h /= 6;
			}
			$h = (int) round( $h * 360 );
			$s = (int) round( $s * 100 );
			$l = (int) round( $l * 100 );
			return compact( 'h', 's', 'l' );
		}

/**
		 * From a color code to a string to be used in CSS declaration.
		 *
		 * @param string $type  Color code type.
		 * @param int    $alpha Transparency.
		 *
		 * @return string
		 */
		public function toCSS( $type = 'hex', $alpha = 1 ) {
			switch ( $type ) {
				case 'hex':
					return $this->toString();
				case 'rgb':
				case 'rgba':
					list( $r, $g, $b ) = array_values( $this->toRgbInt() );
					if ( is_numeric( $alpha ) && $alpha < 1 ) {
						return "rgba( {$r}, {$g}, {$b}, $alpha )";
					} else {
						return "rgb( {$r}, {$g}, {$b} )";
					}
				case 'hsl':
				case 'hsla':
					list( $h, $s, $l ) = array_values( $this->toHsl() );
					if ( is_numeric( $alpha ) && $alpha < 1 ) {
						return "hsla( {$h}, {$s}, {$l}, $alpha )";
					} else {
						return "hsl( {$h}, {$s}, {$l} )";
					}
				default:
					return $this->toString();
			}
		}

/**
		 * Get current color in XYZ format
		 *
		 * @return array
		 */
		public function toXyz() {
			$rgb = $this->toRgbInt();

// Normalize RGB values to 1.
			$rgb_new = array();
			foreach ( $rgb as $item ) {
				$rgb_new[] = $item / 255;
			}
			$rgb = $rgb_new;

$rgb_new = array();
			foreach ( $rgb as $item ) {
				if ( $item > 0.04045 ) {
					$item = pow( ( ( $item + 0.055 ) / 1.055 ), 2.4 );
				} else {
					$item = $item / 12.92;
				}
				$rgb_new[] = $item * 100;
			}
			$rgb = $rgb_new;

// Observer. = 2°, Illuminant = D65.
			$xyz = array(
				'x' => ( $rgb['red'] * 0.4124 ) + ( $rgb['green'] * 0.3576 ) + ( $rgb['blue'] * 0.1805 ),
				'y' => ( $rgb['red'] * 0.2126 ) + ( $rgb['green'] * 0.7152 ) + ( $rgb['blue'] * 0.0722 ),
				'z' => ( $rgb['red'] * 0.0193 ) + ( $rgb['green'] * 0.1192 ) + ( $rgb['blue'] * 0.9505 ),
			);

return $xyz;
		}

/**
		 * Get color CIE-Lab values
		 *
		 * @return array
		 */
		public function toLabCie() {
			$xyz = $this->toXyz();

// Ovserver = 2*, Iluminant=D65.
			$xyz['x'] /= 95.047;
			$xyz['y'] /= 100;
			$xyz['z'] /= 108.883;

$xyz_new = array();
			foreach ( $xyz as $item ) {
				if ( $item > 0.008856 ) {
					$xyz_new[] = pow( $item, 1 / 3 );
				} else {
					$xyz_new[] = ( 7.787 * $item ) + ( 16 / 116 );
				}
			}
			$xyz = $xyz_new;

$lab = array(
				'l' => ( 116 * $xyz['y'] ) - 16,
				'a' => 500 * ( $xyz['x'] - $xyz['y'] ),
				'b' => 200 * ( $xyz['y'] - $xyz['z'] ),
			);

return $lab;
		}

/**
		 * Convert color to integer
		 *
		 * @return int
		 */
		public function toInt() {
			return $this->color;
		}

/**
		 * Alias of toString()
		 *
		 * @return string
		 */
		public function __toString() {
			return $this->toString();
		}

/**
		 * Get color as string
		 *
		 * @return string
		 */
		public function toString() {
			$str = $this->toHex();
			return strtoupper( "#{$str}" );
		}

/**
		 * Get the distance between this color and the given color
		 *
		 * @param Jetpack_Color $color Color code.
		 *
		 * @return int
		 */
		public function getDistanceRgbFrom( Jetpack_Color $color ) {
			$rgb1 = $this->toRgbInt();
			$rgb2 = $color->toRgbInt();

$r_diff = abs( $rgb1['red'] - $rgb2['red'] );
			$g_diff = abs( $rgb1['green'] - $rgb2['green'] );
			$b_diff = abs( $rgb1['blue'] - $rgb2['blue'] );

// Sum of RGB differences.
			$diff = $r_diff + $g_diff + $b_diff;
			return $diff;
		}

/**
		 * Get distance from the given color using the Delta E method
		 *
		 * @param Jetpack_Color $color Color code.
		 *
		 * @return float
		 */
		public function getDistanceLabFrom( Jetpack_Color $color ) {
			$lab1 = $this->toLabCie();
			$lab2 = $color->toLabCie();

$l_diff = abs( $lab2['l'] - $lab1['l'] );
			$a_diff = abs( $lab2['a'] - $lab1['a'] );
			$b_diff = abs( $lab2['b'] - $lab1['b'] );

$delta = sqrt( $l_diff + $a_diff + $b_diff );

return $delta;
		}

/**
		 * Calculate luminosity.
		 *
		 * @return float
		 */
		public function toLuminosity() {
			$lum = array();
			foreach ( $this->toRgbInt() as $slot => $value ) {
				$chan         = $value / 255;
				$lum[ $slot ] = ( $chan <= 0.03928 ) ? $chan / 12.92 : pow( ( ( $chan + 0.055 ) / 1.055 ), 2.4 );
			}
			return 0.2126 * $lum['red'] + 0.7152 * $lum['green'] + 0.0722 * $lum['blue'];
		}

/**
		 * Get distance between colors using luminance.
		 * Should be more than 5 for readable contrast
		 *
		 * @param  Jetpack_Color $color Another color.
		 * @return float
		 */
		public function getDistanceLuminosityFrom( Jetpack_Color $color ) {
			$l1 = $this->toLuminosity();
			$l2 = $color->toLuminosity();
			if ( $l1 > $l2 ) {
				return ( $l1 + 0.05 ) / ( $l2 + 0.05 );
			} else {
				return ( $l2 + 0.05 ) / ( $l1 + 0.05 );
			}
		}

/**
		 * Get maximum contrast color.
		 *
		 * @return $this
		 */
		public function getMaxContrastColor() {
			$with_black = $this->getDistanceLuminosityFrom( new Jetpack_Color( '#000' ) );
			$with_white = $this->getDistanceLuminosityFrom( new Jetpack_Color( '#fff' ) );
			$color      = new Jetpack_Color();
			$hex        = ( $with_black >= $with_white ) ? '#000000' : '#ffffff';
			return $color->fromHex( $hex );
		}

/**
		 * Get grayscale contrasting color.
		 *
		 * @param bool|int $contrast Contrast.
		 *
		 * @return $this
		 */
		public function getGrayscaleContrastingColor( $contrast = false ) {
			if ( ! $contrast ) {
				return $this->getMaxContrastColor();
			}
			// don't allow less than 5.
			$target_contrast = ( $contrast < 5 ) ? 5 : $contrast;
			$color           = $this->getMaxContrastColor();
			$contrast        = $color->getDistanceLuminosityFrom( $this );

// if current max contrast is less than the target contrast, we had wishful thinking.
			if ( $contrast <= $target_contrast ) {
				return $color;
			}

$incr = ( '#000000' === $color->toString() ) ? 1 : -1;
			while ( $contrast > $target_contrast ) {
				$color    = $color->incrementLightness( $incr );
				$contrast = $color->getDistanceLuminosityFrom( $this );
			}

return $color;
		}

/**
		 * Gets a readable contrasting color. $this is assumed to be the text and $color the background color.
		 *
		 * @param  object  $bg_color      A Color object that will be compared against $this.
		 * @param  integer $min_contrast The minimum contrast to achieve, if possible.
		 * @return object                A Color object, an increased contrast $this compared against $bg_color
		 */
		public function getReadableContrastingColor( $bg_color = false, $min_contrast = 5 ) {
			if ( ! $bg_color || ! is_a( $bg_color, 'Jetpack_Color' ) ) {
				return $this;
			}
			// you shouldn't use less than 5, but you might want to.
			$target_contrast = $min_contrast;
			// working things.
			$contrast           = $bg_color->getDistanceLuminosityFrom( $this );
			$max_contrast_color = $bg_color->getMaxContrastColor();
			$max_contrast       = $max_contrast_color->getDistanceLuminosityFrom( $bg_color );

// if current max contrast is less than the target contrast, we had wishful thinking.
			// still, go max.
			if ( $max_contrast <= $target_contrast ) {
				return $max_contrast_color;
			}
			// or, we might already have sufficient contrast.
			if ( $contrast >= $target_contrast ) {
				return $this;
			}

$incr = ( 0 === $max_contrast_color->toInt() ) ? -1 : 1;
			while ( $contrast < $target_contrast ) {
				$this->incrementLightness( $incr );
				$contrast = $bg_color->getDistanceLuminosityFrom( $this );
				// infininite loop prevention: you never know.
				if ( 0 === $this->color || 16777215 === $this->color ) {
					break;
				}
			}

return $this;
		}

/**
		 * Detect if color is grayscale
		 *
		 * @param int $threshold Max difference between colors.
		 *
		 * @return bool
		 */
		public function isGrayscale( $threshold = 16 ) {
			$rgb = $this->toRgbInt();

// Get min and max rgb values, then difference between them.
			$rgb_min = min( $rgb );
			$rgb_max = max( $rgb );
			$diff    = $rgb_max - $rgb_min;

return $diff < $threshold;
		}

/**
		 * Get the closest matching color from the given array of colors
		 *
		 * @param array $colors array of integers or Jetpack_Color objects.
		 *
		 * @return mixed the array key of the matched color
		 */
		public function getClosestMatch( array $colors ) {
			$match_dist = 10000;
			$match_key  = null;
			foreach ( $colors as $key => $color ) {
				if ( false === ( $color instanceof Jetpack_Color ) ) {
					$c = new Jetpack_Color( $color );
				}
				$dist = $this->getDistanceLabFrom( $c );
				if ( $dist < $match_dist ) {
					$match_dist = $dist;
					$match_key  = $key;
				}
			}

return $match_key;
		}

/* TRANSFORMS */

/**
		 * Transform -- Darken color.
		 *
		 * @param int $amount Amount. Default to 5.
		 *
		 * @return $this
		 */
		public function darken( $amount = 5 ) {
			return $this->incrementLightness( - $amount );
		}

/**
		 * Transform -- Lighten color.
		 *
		 * @param int $amount Amount. Default to 5.
		 *
		 * @return $this
		 */
		public function lighten( $amount = 5 ) {
			return $this->incrementLightness( $amount );
		}

/**
		 * Transform -- Increment lightness.
		 *
		 * @param int $amount Amount.
		 *
		 * @return $this
		 */
		public function incrementLightness( $amount ) {
			$hsl = $this->toHsl();

$h = isset( $hsl['h'] ) ? $hsl['h'] : 0;
			$s = isset( $hsl['s'] ) ? $hsl['s'] : 0;
			$l = isset( $hsl['l'] ) ? $hsl['l'] : 0;

$l += $amount;
			if ( $l < 0 ) {
				$l = 0;
			}
			if ( $l > 100 ) {
				$l = 100;
			}
			return $this->fromHsl( $h, $s, $l );
		}

/**
		 * Transform -- Saturate color.
		 *
		 * @param int $amount Amount. Default to 15.
		 *
		 * @return $this
		 */
		public function saturate( $amount = 15 ) {
			return $this->incrementSaturation( $amount );
		}

/**
		 * Transform -- Desaturate color.
		 *
		 * @param int $amount Amount. Default to 15.
		 *
		 * @return $this
		 */
		public function desaturate( $amount = 15 ) {
			return $this->incrementSaturation( - $amount );
		}

/**
		 * Transform -- Increment saturation.
		 *
		 * @param int $amount Amount.
		 *
		 * @return $this
		 */
		public function incrementSaturation( $amount ) {
			$hsl = $this->toHsl();

$h = isset( $hsl['h'] ) ? $hsl['h'] : 0;
			$s = isset( $hsl['s'] ) ? $hsl['s'] : 0;
			$l = isset( $hsl['l'] ) ? $hsl['l'] : 0;

$s += $amount;
			if ( $s < 0 ) {
				$s = 0;
			}
			if ( $s > 100 ) {
				$s = 100;
			}
			return $this->fromHsl( $h, $s, $l );
		}

/**
		 * Transform -- To grayscale.
		 *
		 * @return $this
		 */
		public function toGrayscale() {
			$hsl = $this->toHsl();

$h = isset( $hsl['h'] ) ? $hsl['h'] : 0;
			$s = 0;
			$l = isset( $hsl['l'] ) ? $hsl['l'] : 0;

return $this->fromHsl( $h, $s, $l );
		}

/**
		 * Transform -- To the complementary color.
		 *
		 * The complement is the color on the opposite side of the color wheel, 180° away.
		 *
		 * @return $this
		 */
		public function getComplement() {
			return $this->incrementHue( 180 );
		}

/**
		 * Transform -- To an analogous color of the complement.
		 *
		 * @param int $step Pass `1` or `-1` to choose which direction around the color wheel.
		 *
		 * @return $this
		 */
		public function getSplitComplement( $step = 1 ) {
			$incr = 180 + ( $step * 30 );
			return $this->incrementHue( $incr );
		}

/**
		 * Transform -- To an analogous color.
		 *
		 * Analogous colors are those adjacent on the color wheel, separated by 30°.
		 *
		 * @param int $step Pass `1` or `-1` to choose which direction around the color wheel.
		 *
		 * @return $this
		 */
		public function getAnalog( $step = 1 ) {
			$incr = $step * 30;
			return $this->incrementHue( $incr );
		}

/**
		 * Transform -- To a tetradic (rectangular) color.
		 *
		 * A rectangular color scheme uses a color, its complement, and the colors 60° from each.
		 * This transforms the color to its 60° "tetrad".
		 *
		 * @param int $step Pass `1` or `-1` to choose which direction around the color wheel.
		 *
		 * @return $this
		 */
		public function getTetrad( $step = 1 ) {
			$incr = $step * 60;
			return $this->incrementHue( $incr );
		}

/**
		 * Transform -- To a triadic color.
		 *
		 * A triadic color scheme uses three colors evenly spaced (120°) around the color wheel.
		 * This transforms the color to one of its triadic colors.
		 *
		 * @param int $step Pass `1` or `-1` to choose which direction around the color wheel.
		 *
		 * @return $this
		 */
		public function getTriad( $step = 1 ) {
			$incr = $step * 120;
			return $this->incrementHue( $incr );
		}

/**
		 * Transform -- Increment hue.
		 *
		 * @param int $amount Amount.
		 *
		 * @return $this
		 */
		public function incrementHue( $amount ) {
			$hsl = $this->toHsl();

$h = isset( $hsl['h'] ) ? $hsl['h'] : 0;
			$s = isset( $hsl['s'] ) ? $hsl['s'] : 0;
			$l = isset( $hsl['l'] ) ? $hsl['l'] : 0;

$h = ( $h + $amount ) % 360;
			if ( $h < 0 ) {
				$h += 360;
			}
			return $this->fromHsl( $h, $s, $l );
		}
	}
}

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