class.color.php — Jetpack – WP Security, Backup, Speed, & Growth 12.3.2

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class.color.php

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1	<?php // phpcs:ignore WordPress.Files.FileName.InvalidClassFileName
2	/**
3	* Color utility and conversion
4	*
5	* Represents a color value, and converts between RGB/HSV/XYZ/Lab/HSL
6	*
7	* Example:
8	* $color = new Jetpack_Color(0xFFFFFF);
9	*
10	* @author Harold Asbridge <hasbridge@gmail.com>
11	* @author Matt Wiebe <wiebe@automattic.com>
12	* @license https://www.opensource.org/licenses/MIT
13	*
14	* @package automattic/jetpack
15	*/
16
17	// phpcs:disable WordPress.NamingConventions.ValidFunctionName.MethodNameInvalid
18
19	/**
20	* Color utilities
21	*/
22	class Jetpack_Color {
23	/**
24	* Color code (later array or string, depending on type)
25	*
26	* @var int\|array\|string
27	*/
28	protected $color = 0;
29
30	/**
31	* Initialize object
32	*
33	* @param string\|array $color A color of the type $type.
34	* @param string $type The type of color we will construct from.
35	* One of hex (default), rgb, hsl, int.
36	*/
37	public function __construct( $color = null, $type = 'hex' ) {
38	if ( $color ) {
39	switch ( $type ) {
40	case 'hex':
41	$this->fromHex( $color );
42	break;
43	case 'rgb':
44	if ( is_array( $color ) && count( $color ) === 3 ) {
45	list( $r, $g, $b ) = array_values( $color );
46	$this->fromRgbInt( $r, $g, $b );
47	}
48	break;
49	case 'hsl':
50	if ( is_array( $color ) && count( $color ) === 3 ) {
51	list( $h, $s, $l ) = array_values( $color );
52	$this->fromHsl( $h, $s, $l );
53	}
54	break;
55	case 'int':
56	$this->fromInt( $color );
57	break;
58	default:
59	// there is no default.
60	break;
61	}
62	}
63	}
64
65	/**
66	* Init color from hex value
67	*
68	* @param string $hex_value Color hex value.
69	*
70	* @return $this
71	* @throws RangeException Invalid color code range error.
72	*/
73	public function fromHex( $hex_value ) {
74	$hex_value = str_replace( '#', '', $hex_value );
75	// handle short hex codes like #fff.
76	if ( 3 === strlen( $hex_value ) ) {
77	$hex_value = $hex_value[0] . $hex_value[0] . $hex_value[1] . $hex_value[1] . $hex_value[2] . $hex_value[2];
78	}
79	return $this->fromInt( hexdec( $hex_value ) );
80	}
81
82	/**
83	* Init color from integer RGB values
84	*
85	* @param int $red Red color code.
86	* @param int $green Green color code.
87	* @param int $blue Blue color code.
88	*
89	* @return $this
90	* @throws RangeException Invalid color code range error.
91	*/
92	public function fromRgbInt( $red, $green, $blue ) {
93	if ( $red < 0 \|\| $red > 255 ) {
94	throw new RangeException( 'Red value ' . $red . ' out of valid color code range' );
95	}
96
97	if ( $green < 0 \|\| $green > 255 ) {
98	throw new RangeException( 'Green value ' . $green . ' out of valid color code range' );
99	}
100
101	if ( $blue < 0 \|\| $blue > 255 ) {
102	throw new RangeException( 'Blue value ' . $blue . ' out of valid color code range' );
103	}
104
105	$this->color = (int) ( ( $red << 16 ) + ( $green << 8 ) + $blue );
106
107	return $this;
108	}
109
110	/**
111	* Init color from hex RGB values
112	*
113	* @param string $red Red color code.
114	* @param string $green Green color code.
115	* @param string $blue Blue color code.
116	*
117	* @return $this
118	*/
119	public function fromRgbHex( $red, $green, $blue ) {
120	return $this->fromRgbInt( hexdec( $red ), hexdec( $green ), hexdec( $blue ) );
121	}
122
123	/**
124	* Converts an HSL color value to RGB. Conversion formula
125	* adapted from https://en.wikipedia.org/wiki/HSL_color_space.
126	*
127	* @param int $h Hue. [0-360].
128	* @param int $s Saturation [0, 100].
129	* @param int $l Lightness [0, 100].
130	*/
131	public function fromHsl( $h, $s, $l ) {
132	$h /= 360;
133	$s /= 100;
134	$l /= 100;
135
136	if ( 0 === $s ) {
137	// achromatic.
138	$r = $l;
139	$g = $l;
140	$b = $l;
141	} else {
142	$q = $l < 0.5 ? $l * ( 1 + $s ) : $l + $s - $l * $s;
143	$p = 2 * $l - $q;
144	$r = $this->hue2rgb( $p, $q, $h + 1 / 3 );
145	$g = $this->hue2rgb( $p, $q, $h );
146	$b = $this->hue2rgb( $p, $q, $h - 1 / 3 );
147	}
148
149	return $this->fromRgbInt( $r * 255, $g * 255, $b * 255 );
150	}
151
152	/**
153	* Helper function for Jetpack_Color::fromHsl()
154	*
155	* @param float $p Minimum of R/G/B [0, 1].
156	* @param float $q Maximum of R/G/B [0, 1].
157	* @param float $t Adjusted hue [0, 1].
158	*/
159	private function hue2rgb( $p, $q, $t ) {
160	if ( $t < 0 ) {
161	++$t;
162	}
163	if ( $t > 1 ) {
164	--$t;
165	}
166	if ( $t < 1 / 6 ) {
167	return $p + ( $q - $p ) * 6 * $t;
168	}
169	if ( $t < 1 / 2 ) {
170	return $q;
171	}
172	if ( $t < 2 / 3 ) {
173	return $p + ( $q - $p ) * ( 2 / 3 - $t ) * 6;
174	}
175	return $p;
176	}
177
178	/**
179	* Init color from integer value
180	*
181	* @param int $int_value Color code.
182	*
183	* @return $this
184	* @throws RangeException Invalid color code range error.
185	*/
186	public function fromInt( $int_value ) {
187	if ( $int_value < 0 \|\| $int_value > 16777215 ) {
188	throw new RangeException( $int_value . ' out of valid color code range' );
189	}
190
191	$this->color = $int_value;
192
193	return $this;
194	}
195
196	/**
197	* Convert color to hex
198	*
199	* @return string
200	*/
201	public function toHex() {
202	return sprintf( '%06x', $this->color );
203	}
204
205	/**
206	* Convert color to RGB array (integer values)
207	*
208	* @return array
209	*/
210	public function toRgbInt() {
211	return array(
212	'red' => (int) ( 255 & ( $this->color >> 16 ) ),
213	'green' => (int) ( 255 & ( $this->color >> 8 ) ),
214	'blue' => (int) ( 255 & ( $this->color ) ),
215	);
216	}
217
218	/**
219	* Convert color to RGB array (hex values)
220	*
221	* @return array
222	*/
223	public function toRgbHex() {
224	$r = array();
225	foreach ( $this->toRgbInt() as $item ) {
226	$r[] = dechex( $item );
227	}
228	return $r;
229	}
230
231	/**
232	* Get Hue/Saturation/Value for the current color
233	* (float values, slow but accurate)
234	*
235	* @return array
236	*/
237	public function toHsvFloat() {
238	$rgb = $this->toRgbInt();
239
240	$rgb_min = min( $rgb );
241	$rgb_max = max( $rgb );
242
243	$hsv = array(
244	'hue' => 0,
245	'sat' => 0,
246	'val' => $rgb_max,
247	);
248
249	// If v is 0, color is black.
250	if ( 0 === $hsv['val'] ) {
251	return $hsv;
252	}
253
254	// Normalize RGB values to 1.
255	$rgb['red'] /= $hsv['val'];
256	$rgb['green'] /= $hsv['val'];
257	$rgb['blue'] /= $hsv['val'];
258	$rgb_min = min( $rgb );
259	$rgb_max = max( $rgb );
260
261	// Calculate saturation.
262	$hsv['sat'] = $rgb_max - $rgb_min;
263	if ( 0 === $hsv['sat'] ) {
264	$hsv['hue'] = 0;
265	return $hsv;
266	}
267
268	// Normalize saturation to 1.
269	$rgb['red'] = ( $rgb['red'] - $rgb_min ) / ( $rgb_max - $rgb_min );
270	$rgb['green'] = ( $rgb['green'] - $rgb_min ) / ( $rgb_max - $rgb_min );
271	$rgb['blue'] = ( $rgb['blue'] - $rgb_min ) / ( $rgb_max - $rgb_min );
272	$rgb_min = min( $rgb );
273	$rgb_max = max( $rgb );
274
275	// Calculate hue.
276	if ( $rgb_max === $rgb['red'] ) {
277	$hsv['hue'] = 0.0 + 60 * ( $rgb['green'] - $rgb['blue'] );
278	if ( $hsv['hue'] < 0 ) {
279	$hsv['hue'] += 360;
280	}
281	} elseif ( $rgb_max === $rgb['green'] ) {
282	$hsv['hue'] = 120 + ( 60 * ( $rgb['blue'] - $rgb['red'] ) );
283	} else {
284	$hsv['hue'] = 240 + ( 60 * ( $rgb['red'] - $rgb['green'] ) );
285	}
286
287	return $hsv;
288	}
289
290	/**
291	* Get HSV values for color
292	* (integer values from 0-255, fast but less accurate)
293	*
294	* @return array
295	*/
296	public function toHsvInt() {
297	$rgb = $this->toRgbInt();
298
299	$rgb_min = min( $rgb );
300	$rgb_max = max( $rgb );
301
302	$hsv = array(
303	'hue' => 0,
304	'sat' => 0,
305	'val' => $rgb_max,
306	);
307
308	// If value is 0, color is black.
309	if ( 0 === $hsv['val'] ) {
310	return $hsv;
311	}
312
313	// Calculate saturation.
314	$hsv['sat'] = round( 255 * ( $rgb_max - $rgb_min ) / $hsv['val'] );
315	if ( 0 === $hsv['sat'] ) {
316	$hsv['hue'] = 0;
317	return $hsv;
318	}
319
320	// Calculate hue.
321	if ( $rgb_max === $rgb['red'] ) {
322	$hsv['hue'] = round( 0 + 43 * ( $rgb['green'] - $rgb['blue'] ) / ( $rgb_max - $rgb_min ) );
323	} elseif ( $rgb_max === $rgb['green'] ) {
324	$hsv['hue'] = round( 85 + 43 * ( $rgb['blue'] - $rgb['red'] ) / ( $rgb_max - $rgb_min ) );
325	} else {
326	$hsv['hue'] = round( 171 + 43 * ( $rgb['red'] - $rgb['green'] ) / ( $rgb_max - $rgb_min ) );
327	}
328	if ( $hsv['hue'] < 0 ) {
329	$hsv['hue'] += 255;
330	}
331
332	return $hsv;
333	}
334
335	/**
336	* Converts an RGB color value to HSL. Conversion formula
337	* adapted from https://en.wikipedia.org/wiki/HSL_color_space.
338	* Assumes r, g, and b are contained in the set [0, 255] and
339	* returns h in [0, 360], s in [0, 100], l in [0, 100]
340	*
341	* @return Array The HSL representation
342	*/
343	public function toHsl() {
344	list( $r, $g, $b ) = array_values( $this->toRgbInt() );
345	$r /= 255;
346	$g /= 255;
347	$b /= 255;
348	$max = max( $r, $g, $b );
349	$min = min( $r, $g, $b );
350	$l = ( $max + $min ) / 2;
351
352	if ( $max === $min ) {
353	// achromatic.
354	$s = 0;
355	$h = 0;
356	} else {
357	$d = $max - $min;
358	$s = $l > 0.5 ? $d / ( 2 - $max - $min ) : $d / ( $max + $min );
359	switch ( $max ) {
360	case $r:
361	$h = ( $g - $b ) / $d + ( $g < $b ? 6 : 0 );
362	break;
363	case $g:
364	$h = ( $b - $r ) / $d + 2;
365	break;
366	case $b:
367	$h = ( $r - $g ) / $d + 4;
368	break;
369	}
370	$h /= 6;
371	}
372	$h = (int) round( $h * 360 );
373	$s = (int) round( $s * 100 );
374	$l = (int) round( $l * 100 );
375	return compact( 'h', 's', 'l' );
376	}
377
378	/**
379	* From a color code to a string to be used in CSS declaration.
380	*
381	* @param string $type Color code type.
382	* @param int $alpha Transparency.
383	*
384	* @return string
385	*/
386	public function toCSS( $type = 'hex', $alpha = 1 ) {
387	switch ( $type ) {
388	case 'hex':
389	return $this->toString();
390	case 'rgb':
391	case 'rgba':
392	list( $r, $g, $b ) = array_values( $this->toRgbInt() );
393	if ( is_numeric( $alpha ) && $alpha < 1 ) {
394	return "rgba( {$r}, {$g}, {$b}, $alpha )";
395	} else {
396	return "rgb( {$r}, {$g}, {$b} )";
397	}
398	case 'hsl':
399	case 'hsla':
400	list( $h, $s, $l ) = array_values( $this->toHsl() );
401	if ( is_numeric( $alpha ) && $alpha < 1 ) {
402	return "hsla( {$h}, {$s}, {$l}, $alpha )";
403	} else {
404	return "hsl( {$h}, {$s}, {$l} )";
405	}
406	default:
407	return $this->toString();
408	}
409	}
410
411	/**
412	* Get current color in XYZ format
413	*
414	* @return array
415	*/
416	public function toXyz() {
417	$rgb = $this->toRgbInt();
418
419	// Normalize RGB values to 1.
420	$rgb_new = array();
421	foreach ( $rgb as $item ) {
422	$rgb_new[] = $item / 255;
423	}
424	$rgb = $rgb_new;
425
426	$rgb_new = array();
427	foreach ( $rgb as $item ) {
428	if ( $item > 0.04045 ) {
429	$item = pow( ( ( $item + 0.055 ) / 1.055 ), 2.4 );
430	} else {
431	$item = $item / 12.92;
432	}
433	$rgb_new[] = $item * 100;
434	}
435	$rgb = $rgb_new;
436
437	// Observer. = 2°, Illuminant = D65.
438	$xyz = array(
439	'x' => ( $rgb['red'] * 0.4124 ) + ( $rgb['green'] * 0.3576 ) + ( $rgb['blue'] * 0.1805 ),
440	'y' => ( $rgb['red'] * 0.2126 ) + ( $rgb['green'] * 0.7152 ) + ( $rgb['blue'] * 0.0722 ),
441	'z' => ( $rgb['red'] * 0.0193 ) + ( $rgb['green'] * 0.1192 ) + ( $rgb['blue'] * 0.9505 ),
442	);
443
444	return $xyz;
445	}
446
447	/**
448	* Get color CIE-Lab values
449	*
450	* @return array
451	*/
452	public function toLabCie() {
453	$xyz = $this->toXyz();
454
455	// Ovserver = 2*, Iluminant=D65.
456	$xyz['x'] /= 95.047;
457	$xyz['y'] /= 100;
458	$xyz['z'] /= 108.883;
459
460	$xyz_new = array();
461	foreach ( $xyz as $item ) {
462	if ( $item > 0.008856 ) {
463	$xyz_new[] = pow( $item, 1 / 3 );
464	} else {
465	$xyz_new[] = ( 7.787 * $item ) + ( 16 / 116 );
466	}
467	}
468	$xyz = $xyz_new;
469
470	$lab = array(
471	'l' => ( 116 * $xyz['y'] ) - 16,
472	'a' => 500 * ( $xyz['x'] - $xyz['y'] ),
473	'b' => 200 * ( $xyz['y'] - $xyz['z'] ),
474	);
475
476	return $lab;
477	}
478
479	/**
480	* Convert color to integer
481	*
482	* @return int
483	*/
484	public function toInt() {
485	return $this->color;
486	}
487
488	/**
489	* Alias of toString()
490	*
491	* @return string
492	*/
493	public function __toString() {
494	return $this->toString();
495	}
496
497	/**
498	* Get color as string
499	*
500	* @return string
501	*/
502	public function toString() {
503	$str = $this->toHex();
504	return strtoupper( "#{$str}" );
505	}
506
507	/**
508	* Get the distance between this color and the given color
509	*
510	* @param Jetpack_Color $color Color code.
511	*
512	* @return int
513	*/
514	public function getDistanceRgbFrom( Jetpack_Color $color ) {
515	$rgb1 = $this->toRgbInt();
516	$rgb2 = $color->toRgbInt();
517
518	$r_diff = abs( $rgb1['red'] - $rgb2['red'] );
519	$g_diff = abs( $rgb1['green'] - $rgb2['green'] );
520	$b_diff = abs( $rgb1['blue'] - $rgb2['blue'] );
521
522	// Sum of RGB differences.
523	$diff = $r_diff + $g_diff + $b_diff;
524	return $diff;
525	}
526
527	/**
528	* Get distance from the given color using the Delta E method
529	*
530	* @param Jetpack_Color $color Color code.
531	*
532	* @return float
533	*/
534	public function getDistanceLabFrom( Jetpack_Color $color ) {
535	$lab1 = $this->toLabCie();
536	$lab2 = $color->toLabCie();
537
538	$l_diff = abs( $lab2['l'] - $lab1['l'] );
539	$a_diff = abs( $lab2['a'] - $lab1['a'] );
540	$b_diff = abs( $lab2['b'] - $lab1['b'] );
541
542	$delta = sqrt( $l_diff + $a_diff + $b_diff );
543
544	return $delta;
545	}
546
547	/**
548	* Calculate luminosity.
549	*
550	* @return float
551	*/
552	public function toLuminosity() {
553	$lum = array();
554	foreach ( $this->toRgbInt() as $slot => $value ) {
555	$chan = $value / 255;
556	$lum[ $slot ] = ( $chan <= 0.03928 ) ? $chan / 12.92 : pow( ( ( $chan + 0.055 ) / 1.055 ), 2.4 );
557	}
558	return 0.2126 * $lum['red'] + 0.7152 * $lum['green'] + 0.0722 * $lum['blue'];
559	}
560
561	/**
562	* Get distance between colors using luminance.
563	* Should be more than 5 for readable contrast
564	*
565	* @param Jetpack_Color $color Another color.
566	* @return float
567	*/
568	public function getDistanceLuminosityFrom( Jetpack_Color $color ) {
569	$l1 = $this->toLuminosity();
570	$l2 = $color->toLuminosity();
571	if ( $l1 > $l2 ) {
572	return ( $l1 + 0.05 ) / ( $l2 + 0.05 );
573	} else {
574	return ( $l2 + 0.05 ) / ( $l1 + 0.05 );
575	}
576	}
577
578	/**
579	* Get maximum contrast color.
580	*
581	* @return $this
582	*/
583	public function getMaxContrastColor() {
584	$with_black = $this->getDistanceLuminosityFrom( new Jetpack_Color( '#000' ) );
585	$with_white = $this->getDistanceLuminosityFrom( new Jetpack_Color( '#fff' ) );
586	$color = new Jetpack_Color();
587	$hex = ( $with_black >= $with_white ) ? '#000000' : '#ffffff';
588	return $color->fromHex( $hex );
589	}
590
591	/**
592	* Get grayscale contrasting color.
593	*
594	* @param bool\|int $contrast Contrast.
595	*
596	* @return $this
597	*/
598	public function getGrayscaleContrastingColor( $contrast = false ) {
599	if ( ! $contrast ) {
600	return $this->getMaxContrastColor();
601	}
602	// don't allow less than 5.
603	$target_contrast = ( $contrast < 5 ) ? 5 : $contrast;
604	$color = $this->getMaxContrastColor();
605	$contrast = $color->getDistanceLuminosityFrom( $this );
606
607	// if current max contrast is less than the target contrast, we had wishful thinking.
608	if ( $contrast <= $target_contrast ) {
609	return $color;
610	}
611
612	$incr = ( '#000000' === $color->toString() ) ? 1 : -1;
613	while ( $contrast > $target_contrast ) {
614	$color = $color->incrementLightness( $incr );
615	$contrast = $color->getDistanceLuminosityFrom( $this );
616	}
617
618	return $color;
619	}
620
621	/**
622	* Gets a readable contrasting color. $this is assumed to be the text and $color the background color.
623	*
624	* @param object $bg_color A Color object that will be compared against $this.
625	* @param integer $min_contrast The minimum contrast to achieve, if possible.
626	* @return object A Color object, an increased contrast $this compared against $bg_color
627	*/
628	public function getReadableContrastingColor( $bg_color = false, $min_contrast = 5 ) {
629	if ( ! $bg_color \|\| ! is_a( $bg_color, 'Jetpack_Color' ) ) {
630	return $this;
631	}
632	// you shouldn't use less than 5, but you might want to.
633	$target_contrast = $min_contrast;
634	// working things.
635	$contrast = $bg_color->getDistanceLuminosityFrom( $this );
636	$max_contrast_color = $bg_color->getMaxContrastColor();
637	$max_contrast = $max_contrast_color->getDistanceLuminosityFrom( $bg_color );
638
639	// if current max contrast is less than the target contrast, we had wishful thinking.
640	// still, go max.
641	if ( $max_contrast <= $target_contrast ) {
642	return $max_contrast_color;
643	}
644	// or, we might already have sufficient contrast.
645	if ( $contrast >= $target_contrast ) {
646	return $this;
647	}
648
649	$incr = ( 0 === $max_contrast_color->toInt() ) ? -1 : 1;
650	while ( $contrast < $target_contrast ) {
651	$this->incrementLightness( $incr );
652	$contrast = $bg_color->getDistanceLuminosityFrom( $this );
653	// infininite loop prevention: you never know.
654	if ( 0 === $this->color \|\| 16777215 === $this->color ) {
655	break;
656	}
657	}
658
659	return $this;
660	}
661
662	/**
663	* Detect if color is grayscale
664	*
665	* @param int $threshold Max difference between colors.
666	*
667	* @return bool
668	*/
669	public function isGrayscale( $threshold = 16 ) {
670	$rgb = $this->toRgbInt();
671
672	// Get min and max rgb values, then difference between them.
673	$rgb_min = min( $rgb );
674	$rgb_max = max( $rgb );
675	$diff = $rgb_max - $rgb_min;
676
677	return $diff < $threshold;
678	}
679
680	/**
681	* Get the closest matching color from the given array of colors
682	*
683	* @param array $colors array of integers or Jetpack_Color objects.
684	*
685	* @return mixed the array key of the matched color
686	*/
687	public function getClosestMatch( array $colors ) {
688	$match_dist = 10000;
689	$match_key = null;
690	foreach ( $colors as $key => $color ) {
691	if ( false === ( $color instanceof Jetpack_Color ) ) {
692	$c = new Jetpack_Color( $color );
693	}
694	$dist = $this->getDistanceLabFrom( $c );
695	if ( $dist < $match_dist ) {
696	$match_dist = $dist;
697	$match_key = $key;
698	}
699	}
700
701	return $match_key;
702	}
703
704	/* TRANSFORMS */
705
706	/**
707	* Transform -- Darken color.
708	*
709	* @param int $amount Amount. Default to 5.
710	*
711	* @return $this
712	*/
713	public function darken( $amount = 5 ) {
714	return $this->incrementLightness( - $amount );
715	}
716
717	/**
718	* Transform -- Lighten color.
719	*
720	* @param int $amount Amount. Default to 5.
721	*
722	* @return $this
723	*/
724	public function lighten( $amount = 5 ) {
725	return $this->incrementLightness( $amount );
726	}
727
728	/**
729	* Transform -- Increment lightness.
730	*
731	* @param int $amount Amount.
732	*
733	* @return $this
734	*/
735	public function incrementLightness( $amount ) {
736	$hsl = $this->toHsl();
737
738	$h = isset( $hsl['h'] ) ? $hsl['h'] : 0;
739	$s = isset( $hsl['s'] ) ? $hsl['s'] : 0;
740	$l = isset( $hsl['l'] ) ? $hsl['l'] : 0;
741
742	$l += $amount;
743	if ( $l < 0 ) {
744	$l = 0;
745	}
746	if ( $l > 100 ) {
747	$l = 100;
748	}
749	return $this->fromHsl( $h, $s, $l );
750	}
751
752	/**
753	* Transform -- Saturate color.
754	*
755	* @param int $amount Amount. Default to 15.
756	*
757	* @return $this
758	*/
759	public function saturate( $amount = 15 ) {
760	return $this->incrementSaturation( $amount );
761	}
762
763	/**
764	* Transform -- Desaturate color.
765	*
766	* @param int $amount Amount. Default to 15.
767	*
768	* @return $this
769	*/
770	public function desaturate( $amount = 15 ) {
771	return $this->incrementSaturation( - $amount );
772	}
773
774	/**
775	* Transform -- Increment saturation.
776	*
777	* @param int $amount Amount.
778	*
779	* @return $this
780	*/
781	public function incrementSaturation( $amount ) {
782	$hsl = $this->toHsl();
783
784	$h = isset( $hsl['h'] ) ? $hsl['h'] : 0;
785	$s = isset( $hsl['s'] ) ? $hsl['s'] : 0;
786	$l = isset( $hsl['l'] ) ? $hsl['l'] : 0;
787
788	$s += $amount;
789	if ( $s < 0 ) {
790	$s = 0;
791	}
792	if ( $s > 100 ) {
793	$s = 100;
794	}
795	return $this->fromHsl( $h, $s, $l );
796	}
797
798	/**
799	* Transform -- To grayscale.
800	*
801	* @return $this
802	*/
803	public function toGrayscale() {
804	$hsl = $this->toHsl();
805
806	$h = isset( $hsl['h'] ) ? $hsl['h'] : 0;
807	$s = 0;
808	$l = isset( $hsl['l'] ) ? $hsl['l'] : 0;
809
810	return $this->fromHsl( $h, $s, $l );
811	}
812
813	/**
814	* Transform -- To the complementary color.
815	*
816	* The complement is the color on the opposite side of the color wheel, 180° away.
817	*
818	* @return $this
819	*/
820	public function getComplement() {
821	return $this->incrementHue( 180 );
822	}
823
824	/**
825	* Transform -- To an analogous color of the complement.
826	*
827	* @param int $step Pass `1` or `-1` to choose which direction around the color wheel.
828	*
829	* @return $this
830	*/
831	public function getSplitComplement( $step = 1 ) {
832	$incr = 180 + ( $step * 30 );
833	return $this->incrementHue( $incr );
834	}
835
836	/**
837	* Transform -- To an analogous color.
838	*
839	* Analogous colors are those adjacent on the color wheel, separated by 30°.
840	*
841	* @param int $step Pass `1` or `-1` to choose which direction around the color wheel.
842	*
843	* @return $this
844	*/
845	public function getAnalog( $step = 1 ) {
846	$incr = $step * 30;
847	return $this->incrementHue( $incr );
848	}
849
850	/**
851	* Transform -- To a tetradic (rectangular) color.
852	*
853	* A rectangular color scheme uses a color, its complement, and the colors 60° from each.
854	* This transforms the color to its 60° "tetrad".
855	*
856	* @param int $step Pass `1` or `-1` to choose which direction around the color wheel.
857	*
858	* @return $this
859	*/
860	public function getTetrad( $step = 1 ) {
861	$incr = $step * 60;
862	return $this->incrementHue( $incr );
863	}
864
865	/**
866	* Transform -- To a triadic color.
867	*
868	* A triadic color scheme uses three colors evenly spaced (120°) around the color wheel.
869	* This transforms the color to one of its triadic colors.
870	*
871	* @param int $step Pass `1` or `-1` to choose which direction around the color wheel.
872	*
873	* @return $this
874	*/
875	public function getTriad( $step = 1 ) {
876	$incr = $step * 120;
877	return $this->incrementHue( $incr );
878	}
879
880	/**
881	* Transform -- Increment hue.
882	*
883	* @param int $amount Amount.
884	*
885	* @return $this
886	*/
887	public function incrementHue( $amount ) {
888	$hsl = $this->toHsl();
889
890	$h = isset( $hsl['h'] ) ? $hsl['h'] : 0;
891	$s = isset( $hsl['s'] ) ? $hsl['s'] : 0;
892	$l = isset( $hsl['l'] ) ? $hsl['l'] : 0;
893
894	$h = ( $h + $amount ) % 360;
895	if ( $h < 0 ) {
896	$h += 360;
897	}
898	return $this->fromHsl( $h, $s, $l );
899	}
900
901	}
902