summaryrefslogtreecommitdiff
path: root/dviware/dvisvgm/src/Color.cpp
blob: bf9a05d7a309ddea6ac2440b201e9b43d38f0b0c (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
/*************************************************************************
** Color.cpp                                                            **
**                                                                      **
** This file is part of dvisvgm -- a fast DVI to SVG converter          **
** Copyright (C) 2005-2020 Martin Gieseking <martin.gieseking@uos.de>   **
**                                                                      **
** This program is free software; you can redistribute it and/or        **
** modify it under the terms of the GNU General Public License as       **
** published by the Free Software Foundation; either version 3 of       **
** the License, or (at your option) any later version.                  **
**                                                                      **
** This program is distributed in the hope that it will be useful, but  **
** WITHOUT ANY WARRANTY; without even the implied warranty of           **
** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the         **
** GNU General Public License for more details.                         **
**                                                                      **
** You should have received a copy of the GNU General Public License    **
** along with this program; if not, see <http://www.gnu.org/licenses/>. **
*************************************************************************/

#include <array>
#include <algorithm>
#include <cctype>
#include <cmath>
#include <cstdlib>
#include <cstring>
#include <iomanip>
#include <sstream>
#include "Color.hpp"
#include "utility.hpp"

using namespace std;

bool Color::SUPPRESS_COLOR_NAMES = true;

const Color Color::BLACK(uint32_t(0));
const Color Color::WHITE(uint8_t(255), uint8_t(255), uint8_t(255));
const Color Color::TRANSPARENT(uint32_t(0xff000000));


static inline uint8_t double_to_byte (double v) {
	v = max(0.0, min(1.0, v));
	return uint8_t(round(255.0*v));
}


Color::Color (const string &psname) {
	if (!setPSName(psname, false))
		setGray(uint8_t(0));
}


void Color::setRGB (double r, double g, double b) {
	setRGB(double_to_byte(r), double_to_byte(g), double_to_byte(b));
}


/** Expects a PostScript color name and sets the color accordingly.
 *  @param[in] name PS color name
 *  @param[in] case_sensitive if true, upper/lower case spelling is significant
 *  @return true if color name could be applied properly */
bool Color::setPSName (string name, bool case_sensitive) {
	if (name[0] == '#') {
		char *p=nullptr;
		_rgb = uint32_t(strtol(name.c_str()+1, &p, 16));
		while (isspace(*p))
			p++;
		return (*p == 0 && _rgb <= 0xFFFFFF);
	}

	struct ColorConstant {
		const char *name;
		const uint32_t rgb;
	};
	// converted color constants from color.pro
	static const array<ColorConstant, 68> constants {{
		{"Apricot",        0xFFAD7A},
		{"Aquamarine",     0x2DFFB2},
		{"Bittersweet",    0xC10200},
		{"Black",          0x000000},
		{"Blue",           0x0000FF},
		{"BlueGreen",      0x26FFAA},
		{"BlueViolet",     0x190CF4},
		{"BrickRed",       0xB70000},
		{"Brown",          0x660000},
		{"BurntOrange",    0xFF7C00},
		{"CadetBlue",      0x606DC4},
		{"CarnationPink",  0xFF5EFF},
		{"Cerulean",       0x0FE2FF},
		{"CornflowerBlue", 0x59DDFF},
		{"Cyan",           0x00FFFF},
		{"Dandelion",      0xFFB528},
		{"DarkOrchid",     0x9932CC},
		{"Emerald",        0x00FF7F},
		{"ForestGreen",    0x00E000},
		{"Fuchsia",        0x7202EA},
		{"Goldenrod",      0xFFE528},
		{"Gray",           0x7F7F7F},
		{"Green",          0x00FF00},
		{"GreenYellow",    0xD8FF4F},
		{"JungleGreen",    0x02FF7A},
		{"Lavender",       0xFF84FF},
		{"LimeGreen",      0x7FFF00},
		{"Magenta",        0xFF00FF},
		{"Mahogany",       0xA50000},
		{"Maroon",         0xAD0000},
		{"Melon",          0xFF897F},
		{"MidnightBlue",   0x007091},
		{"Mulberry",       0xA314F9},
		{"NavyBlue",       0x0F75FF},
		{"OliveGreen",     0x009900},
		{"Orange",         0xFF6321},
		{"OrangeRed",      0xFF007F},
		{"Orchid",         0xAD5BFF},
		{"Peach",          0xFF7F4C},
		{"Periwinkle",     0x6D72FF},
		{"PineGreen",      0x00BF28},
		{"Plum",           0x7F00FF},
		{"ProcessBlue",    0x0AFFFF},
		{"Purple",         0x8C23FF},
		{"RawSienna",      0x8C0000},
		{"Red",            0xFF0000},
		{"RedOrange",      0xFF3A21},
		{"RedViolet",      0x9600A8},
		{"Rhodamine",      0xFF2DFF},
		{"RoyalBlue",      0x007FFF},
		{"RoyalPurple",    0x3F19FF},
		{"RubineRed",      0xFF00DD},
		{"Salmon",         0xFF779E},
		{"SeaGreen",       0x4FFF7F},
		{"Sepia",          0x4C0000},
		{"SkyBlue",        0x60FFE0},
		{"SpringGreen",    0xBCFF3D},
		{"Tan",            0xDB9370},
		{"TealBlue",       0x1EF9A3},
		{"Thistle",        0xE068FF},
		{"Turquoise",      0x26FFCC},
		{"Violet",         0x351EFF},
		{"VioletRed",      0xFF30FF},
		{"White",          0xFFFFFF},
		{"WildStrawberry", 0xFF0A9B},
		{"Yellow",         0xFFFF00},
		{"YellowGreen",    0x8EFF42},
		{"YellowOrange",   0xFF9300},
	}};
	if (case_sensitive) {
		const ColorConstant cmppair = {name.c_str(), 0};
		auto it = lower_bound(constants.begin(), constants.end(), cmppair,
			[](const ColorConstant &c1, const ColorConstant &c2) {
				return strcmp(c1.name, c2.name) < 0;
			}
		);
		if (it != constants.end() && it->name == name) {
			_rgb = it->rgb;
			return true;
		}
	}
	else {
		name = util::tolower(name);
		auto it = find_if(constants.begin(), constants.end(), [&](const ColorConstant &cc) {
			return name == util::tolower(cc.name);
		});
		if (it != constants.end()) {
			_rgb = it->rgb;
			return true;
		}
	}
	return false;
}


void Color::setHSB (double h, double s, double b) {
	valarray<double> hsb(3), rgb(3);
	hsb[0] = h;
	hsb[1] = s;
	hsb[2] = b;
	HSB2RGB(hsb, rgb);
	setRGB(rgb);
}


void Color::setCMYK (double c, double m, double y, double k) {
	valarray<double> cmyk(4), rgb(3);
	cmyk[0] = c;
	cmyk[1] = m;
	cmyk[2] = y;
	cmyk[3] = k;
	CMYK2RGB(cmyk, rgb);
	setRGB(rgb);
}


void Color::setCMYK (const std::valarray<double> &cmyk) {
	valarray<double> rgb(3);
	CMYK2RGB(cmyk, rgb);
	setRGB(rgb);
}


void Color::set (ColorSpace colorSpace, VectorIterator<double> &it) {
	switch (colorSpace) {
		case ColorSpace::GRAY: setGray(*it++); break;
		case ColorSpace::RGB : setRGB(*it, *(it+1), *(it+2)); it+=3; break;
		case ColorSpace::LAB : setLab(*it, *(it+1), *(it+2)); it+=3; break;
		case ColorSpace::CMYK: setCMYK(*it, *(it+1), *(it+2), *(it+3)); it+=4; break;
	}
}


Color Color::operator *= (double c) {
	if (abs(c) < 0.001)
		_rgb &= 0xff000000;
	else if (abs(c-trunc(c)) < 0.999) {
		uint32_t rgb=0;
		for (int i=0; i < 3; i++) {
			rgb |= lround((_rgb & 0xff)*c) << (8*i);
			_rgb >>= 8;
		}
		_rgb = rgb;
	}
	return *this;
}


/** Returns an RGB string representing the color. Depending on the
 *  color value, the string either consists of 3 or 6 hex digits
 *  plus a leading '#' character. */
string Color::rgbString () const {
	ostringstream oss;
	oss << '#';
	for (int i=2; i >= 0; i--) {
		oss << setbase(16) << setfill('0') << setw(2)
			 << (((_rgb >> (8*i)) & 0xff));
	}
	// check if RGB string can be reduced to a three digit hex value
	// #RRGGBB => #RGB, e.g. #112233 => #123
	string hexstr = oss.str();
	if (hexstr[1] == hexstr[2] && hexstr[3] == hexstr[4] && hexstr[5] == hexstr[6]) {
		hexstr[2] = hexstr[3];
		hexstr[3] = hexstr[5];
		hexstr.resize(4);
	}
	return hexstr;
}


/** Returns an SVG color string representing the current color. The result can
 *  either be an SVG color name or an RGB string of the form #RRGGBB. The latter
 *  will be returned if parameter rgbonly is true or if the SVG standard doesn't
 *  define a name for the current color. */
string Color::svgColorString (bool rgbonly) const {
	if (!rgbonly) {
		struct ColorName {
			uint32_t rgb;
			const char *name;
		};
		static const array<ColorName, 138> colornames {{
			{0x000000, "black"},
			{0x000080, "navy"},
			{0x00008b, "darkblue"},
			{0x0000cd, "mediumblue"},
			{0x0000ff, "blue"},
			{0x006400, "darkgreen"},
			{0x008000, "green"},
			{0x008080, "teal"},
			{0x008b8b, "darkcyan"},
			{0x00bfff, "deepskyblue"},
			{0x00ced1, "darkturquoise"},
			{0x00fa9a, "mediumspringgreen"},
			{0x00ff00, "lime"},
			{0x00ff7f, "springgreen"},
			{0x00ffff, "cyan"},
			{0x191970, "midnightblue"},
			{0x1e90ff, "dodgerblue"},
			{0x20b2aa, "lightseagreen"},
			{0x228b22, "forestgreen"},
			{0x2e8b57, "seagreen"},
			{0x2f4f4f, "darkslategray"},
			{0x32cd32, "limegreen"},
			{0x3cb371, "mediumseagreen"},
			{0x40e0d0, "turquoise"},
			{0x4169e1, "royalblue"},
			{0x4682b4, "steelblue"},
			{0x483d8b, "darkslateblue"},
			{0x48d1cc, "mediumturquoise"},
			{0x4b0082, "indigo"},
			{0x556b2f, "darkolivegreen"},
			{0x5f9ea0, "cadetblue"},
			{0x6495ed, "cornflowerblue"},
			{0x66cdaa, "mediumaquamarine"},
			{0x696969, "dimgray"},
			{0x6a5acd, "slateblue"},
			{0x6b8e23, "olivedrab"},
			{0x708090, "slategray"},
			{0x778899, "lightslategray"},
			{0x7b68ee, "mediumslateblue"},
			{0x7cfc00, "lawngreen"},
			{0x7fff00, "chartreuse"},
			{0x7fffd4, "aquamarine"},
			{0x800000, "maroon"},
			{0x800080, "purple"},
			{0x808000, "olive"},
			{0x808080, "gray"},
			{0x87ceeb, "skyblue"},
			{0x87cefa, "lightskyblue"},
			{0x8a2be2, "blueviolet"},
			{0x8b0000, "darkred"},
			{0x8b008b, "darkmagenta"},
			{0x8b4513, "saddlebrown"},
			{0x8fbc8f, "darkseagreen"},
			{0x90ee90, "lightgreen"},
			{0x9370db, "mediumpurple"},
			{0x9400d3, "darkviolet"},
			{0x98fb98, "palegreen"},
			{0x9932cc, "darkorchid"},
			{0x9acd32, "yellowgreen"},
			{0xa0522d, "sienna"},
			{0xa52a2a, "brown"},
			{0xa9a9a9, "darkgray"},
			{0xadd8e6, "lightblue"},
			{0xadff2f, "greenyellow"},
			{0xafeeee, "paleturquoise"},
			{0xb0c4de, "lightsteelblue"},
			{0xb0e0e6, "powderblue"},
			{0xb22222, "firebrick"},
			{0xb8860b, "darkgoldenrod"},
			{0xba55d3, "mediumorchid"},
			{0xbc8f8f, "rosybrown"},
			{0xbdb76b, "darkkhaki"},
			{0xc0c0c0, "silver"},
			{0xc71585, "mediumvioletred"},
			{0xcd5c5c, "indianred"},
			{0xcd853f, "peru"},
			{0xd2691e, "chocolate"},
			{0xd2b48c, "tan"},
			{0xd3d3d3, "lightgray"},
			{0xd8bfd8, "thistle"},
			{0xda70d6, "orchid"},
			{0xdaa520, "goldenrod"},
			{0xdb7093, "palevioletred"},
			{0xdc143c, "crimson"},
			{0xdcdcdc, "gainsboro"},
			{0xdda0dd, "plum"},
			{0xdeb887, "burlywood"},
			{0xe0ffff, "lightcyan"},
			{0xe6e6fa, "lavender"},
			{0xe9967a, "darksalmon"},
			{0xee82ee, "violet"},
			{0xeee8aa, "palegoldenrod"},
			{0xf08080, "lightcoral"},
			{0xf0e68c, "khaki"},
			{0xf0f8ff, "aliceblue"},
			{0xf0fff0, "honeydew"},
			{0xf0ffff, "azure"},
			{0xf4a460, "sandybrown"},
			{0xf5deb3, "wheat"},
			{0xf5f5dc, "beige"},
			{0xf5f5f5, "whitesmoke"},
			{0xf5fffa, "mintcream"},
			{0xf8f8ff, "ghostwhite"},
			{0xfa8072, "salmon"},
			{0xfaebd7, "antiquewhite"},
			{0xfaf0e6, "linen"},
			{0xfafad2, "lightgoldenrodyellow"},
			{0xfdf5e6, "oldlace"},
			{0xff0000, "red"},
			{0xff00ff, "magenta"},
			{0xff1493, "deeppink"},
			{0xff4500, "orangered"},
			{0xff6347, "tomato"},
			{0xff69b4, "hotpink"},
			{0xff7f50, "coral"},
			{0xff8c00, "darkorange"},
			{0xffa07a, "lightsalmon"},
			{0xffa500, "orange"},
			{0xffb6c1, "lightpink"},
			{0xffc0cb, "pink"},
			{0xffd700, "gold"},
			{0xffdab9, "peachpuff"},
			{0xffdead, "navajowhite"},
			{0xffe4b5, "moccasin"},
			{0xffe4c4, "bisque"},
			{0xffe4e1, "mistyrose"},
			{0xffebcd, "blanchedalmond"},
			{0xffefd5, "papayawhip"},
			{0xfff0f5, "lavenderblush"},
			{0xfff5ee, "seashell"},
			{0xfff8dc, "cornsilk"},
			{0xfffacd, "lemonchiffon"},
			{0xfffaf0, "floralwhite"},
			{0xfffafa, "snow"},
			{0xffff00, "yellow"},
			{0xffffe0, "lightyellow"},
			{0xfffff0, "ivory"},
			{0xffffff, "white"}
		}};
		ColorName cmppair = {_rgb, nullptr};
		auto it = lower_bound(colornames.begin(), colornames.end(), cmppair, [](const ColorName &c1, const ColorName &c2) {
			return c1.rgb < c2.rgb;
		});
		if (it != colornames.end() && it->rgb == _rgb)
			return it->name;
	}
	return rgbString();
}


/** Approximates a CMYK color by an RGB triple. The component values
 *  are expected to be normalized, i.e. 0 <= cmyk[i],rgb[j] <= 1.
 *  @param[in]  cmyk color in CMYK space
 *  @param[out] rgb  RGB approximation */
void Color::CMYK2RGB (const valarray<double> &cmyk, valarray<double> &rgb) {
	double kc = 1.0-cmyk[3];
	for (int i=0; i < 3; i++)
		rgb[i] = min(1.0, max(0.0, (1.0-cmyk[i])*kc));
}


void Color::RGB2CMYK (const valarray<double> &rgb, valarray<double> &cmyk) {
	double c = 1-rgb[0];
	double m = 1-rgb[1];
	double y = 1-rgb[2];
	cmyk[3] = min(min(c, m), y);
	cmyk[0] = c-cmyk[3];
	cmyk[1] = m-cmyk[3];
	cmyk[2] = y-cmyk[3];
}


/** Converts a color given in HSB coordinates to RGB.
 *  @param[in]  hsb color in HSB space
 *  @param[out] rgb color in RGB space */
void Color::HSB2RGB (const valarray<double> &hsb, valarray<double> &rgb) {
	if (hsb[1] == 0)
		rgb[0] = rgb[1] = rgb[2] = hsb[2];
	else {
		double h = hsb[0]-floor(hsb[0]);
		int i = int(6*h);
		double f = 6*h-i;
		double p = hsb[2]*(1-hsb[1]);
		double q = hsb[2]*(1-hsb[1]*f);
		double t = hsb[2]*(1-hsb[1]*(1-f));
		switch (i) {
			case 0 : rgb[0]=hsb[2]; rgb[1]=t; rgb[2]=p; break;
			case 1 : rgb[0]=q; rgb[1]=hsb[2]; rgb[2]=p; break;
			case 2 : rgb[0]=p; rgb[1]=hsb[2]; rgb[2]=t; break;
			case 3 : rgb[0]=p; rgb[1]=q; rgb[2]=hsb[2]; break;
			case 4 : rgb[0]=t; rgb[1]=p; rgb[2]=hsb[2]; break;
			case 5 : rgb[0]=hsb[2]; rgb[1]=p; rgb[2]=q; break;
			default: ;  // prevent compiler warning
		}
	}
}


double Color::getGray () const {
	double r, g, b;
	getRGB(r, g, b);
	return r*0.3 + g*0.59 + b*0.11; // gray value according to NTSC video standard
}


void Color::getGray (valarray<double> &gray) const {
	gray.resize(1);
	gray[0] = getGray();
}


void Color::getRGB (double &r, double &g, double &b) const {
	r = ((_rgb >> 16) & 255) / 255.0;
	g = ((_rgb >> 8) & 255) / 255.0;
	b = (_rgb & 255) / 255.0;
}


void Color::getRGB (valarray<double> &rgb) const {
	rgb.resize(3);
	double r, g, b;
	getRGB(r, g, b);
	rgb[0] = r;
	rgb[1] = g;
	rgb[2] = b;
}


void Color::getCMYK (double &c, double &m, double &y, double &k) const {
	valarray<double> rgb(3), cmyk(4);
	getRGB(rgb);
	RGB2CMYK(rgb, cmyk);
	c = cmyk[0];
	m = cmyk[1];
	y = cmyk[2];
	k = cmyk[3];
}


void Color::getCMYK (std::valarray<double> &cmyk) const {
	cmyk.resize(4);
	valarray<double> rgb(3);
	getRGB(rgb);
	RGB2CMYK(rgb, cmyk);
}


void Color::getXYZ (double &x, double &y, double &z) const {
	valarray<double> rgb(3), xyz(3);
	getRGB(rgb);
	RGB2XYZ(rgb, xyz);
	x = xyz[0];
	y = xyz[1];
	z = xyz[2];
}


void Color::setXYZ (double x, double y, double z) {
	valarray<double> xyz(3), rgb(3);
	xyz[0] = x;
	xyz[1] = y;
	xyz[2] = z;
	XYZ2RGB(xyz, rgb);
	setRGB(rgb);
}


void Color::setXYZ (const valarray<double> &xyz) {
	valarray<double> rgb(3);
	XYZ2RGB(xyz, rgb);
	setRGB(rgb);
}


void Color::setLab (double l, double a, double b) {
	valarray<double> lab(3), xyz(3);
	lab[0] = l;
	lab[1] = a;
	lab[2] = b;
	Lab2XYZ(lab, xyz);
	setXYZ(xyz);
}


void Color::setLab (const valarray<double> &lab) {
	valarray<double> xyz(3);
	Lab2XYZ(lab, xyz);
	setXYZ(xyz);
}


/** Get the color in CIELAB color space using the sRGB working space and reference white D65. */
void Color::getLab (double &l, double &a, double &b) const {
	valarray<double> rgb(3), lab(3);
	getRGB(rgb);
	RGB2Lab(rgb, lab);
	l = lab[0];
	a = lab[1];
	b = lab[2];
}


void Color::getLab (std::valarray<double> &lab) const {
	lab.resize(3);
	valarray<double> rgb(3);
	getRGB(rgb);
	RGB2Lab(rgb, lab);
}


// static inline double sqr (double x)  {return x*x;}
static inline double cube (double x) {return x*x*x;}

void Color::Lab2XYZ (const valarray<double> &lab, valarray<double> &xyz) {
	xyz.resize(3);
	double wx=0.95047, wy=1.00, wz=1.08883;  // reference white D65
	double eps = 0.008856;
	double kappa = 903.3;
	double fy = (lab[0]+16)/116;
	double fx = lab[1]/500 + fy;
	double fz = fy - lab[2]/200;
	double xr = (cube(fx) > eps ? cube(fx) : (116*fx-16)/kappa);
	double yr = (lab[0] > kappa*eps ? cube((lab[0]+16)/116) : lab[0]/kappa);
	double zr = (cube(fz) > eps ? cube(fz) : (116*fz-16)/kappa);
	xyz[0] = xr*wx;
	xyz[1] = yr*wy;
	xyz[2] = zr*wz;
}


void Color::XYZ2RGB (const valarray<double> &xyz, valarray<double> &rgb) {
	rgb.resize(3);
	rgb[0] =  3.2404542*xyz[0] - 1.5371385*xyz[1] - 0.4985314*xyz[2];
	rgb[1] = -0.9692660*xyz[0] + 1.8760108*xyz[1] + 0.0415560*xyz[2];
	rgb[2] =  0.0556434*xyz[0] - 0.2040259*xyz[1] + 1.0572252*xyz[2];
	for (int i=0; i < 3; i++)
		rgb[i] = (rgb[i] <= 0.0031308 ? 12.92*rgb[i] : 1.055*pow(rgb[i], 1/2.4)-0.055);
}


void Color::RGB2XYZ (valarray<double> rgb, valarray<double> &xyz) {
	xyz.resize(3);
	for (int i=0; i < 3; i++)
		rgb[i] = (rgb[i] <= 0.04045 ? rgb[i]/12.92 : pow((rgb[i]+0.055)/1.055, 2.4));
	xyz[0] = 0.4124564*rgb[0] + 0.3575761*rgb[1] + 0.1804375*rgb[2];
	xyz[1] = 0.2126729*rgb[0] + 0.7151522*rgb[1] + 0.0721750*rgb[2];
	xyz[2] = 0.0193339*rgb[0] + 0.1191920*rgb[1] + 0.9503041*rgb[2];
}


void Color::RGB2Lab (const valarray<double> &rgb, valarray<double> &lab) {
	double wx=0.95047, wy=1.00, wz=1.08883;  // reference white D65
	double eps = 0.008856;
	double kappa = 903.3;
	valarray<double> xyz(3);
	RGB2XYZ(rgb, xyz);
	xyz[0] /= wx;
	xyz[1] /= wy;
	xyz[2] /= wz;
	double fx = (xyz[0] > eps ? pow(xyz[0], 1.0/3) : (kappa*xyz[0]+16)/116);
	double fy = (xyz[1] > eps ? pow(xyz[1], 1.0/3) : (kappa*xyz[1]+16)/116);
	double fz = (xyz[2] > eps ? pow(xyz[2], 1.0/3) : (kappa*xyz[2]+16)/116);
	lab[0] = 116*fy-16;
	lab[1] = 500*(fx-fy);
	lab[2] = 200*(fy-fz);
}


#if 0
/** Returns the Delta E difference (CIE 2000) between this and another color. */
double Color::deltaE (const Color &c) const {
	double l1, a1, b1;
	double l2, a2, b2;
	getLab(l1, a1, b1);
	c.getLab(l2, a2, b2);
	const double deltaL = l2-l1;
	const double lBar = (l1+l2)/2;
	const double c1 = hypot(a1, b1);
	const double c2 = hypot(a2, b2);
	const double cBar = (c1+c2)/2.0;
	const double g = (1.0-sqrt(pow(cBar, 7.0)/(pow(cBar, 7.0)+6103515625.0)))/2.0;
	const double aa1 = a1*(1.0+g);
	const double aa2 = a2*(1.0+g);
	const double cc1 = hypot(aa1, b1);
	const double cc2 = hypot(aa2, b2);
	const double ccBar = (cc1+cc2)/2.0;
	const double deltaCC = cc2-cc1;
	double hh1 = atan2(b1, aa1);
	if (hh1 < 0) hh1 += deg2rad(360);
	double hh2 = atan2(b2, aa2);
	if (hh2 < 0) hh2 += deg2rad(360);
	const double hhBar = (std::abs(hh1-hh2) > deg2rad(180) ? (hh1+hh2+deg2rad(360)) : (hh1+hh2))/2.0;
	const double t = 1.0
		- 0.17*cos(hhBar-deg2rad(30.0))
		+ 0.24*cos(2.0*hhBar)
		+ 0.32*cos(3.0*hhBar+deg2rad(6.0))
		- 0.20*cos(4.0*hhBar-deg2rad(63.0));
	double deltaHH = hh2-hh1;
	if (deltaHH < deg2rad(-180))
		deltaHH += deg2rad(360);
	else if (deltaHH > deg2rad(180))
		deltaHH -= deg2rad(360);
	const double deltaHHH = 2.0*sqrt(cc1*cc2)*sin(deltaHH/2.0);
	const double sl = 1.0 + 0.015*sqr(lBar-50.0)/sqrt(20.0+sqr(lBar-50.0));
	const double sc = 1.0 + 0.045*ccBar;
	const double sh = 1.0 + 0.015*ccBar*t;
	const double deltaTheta = deg2rad(30)*exp(-sqr((hhBar-deg2rad(275))/deg2rad(25)));
	const double rc = 2.0*sqrt(pow(ccBar, 7)/(pow(ccBar, 7)+6103515625.0));
	const double rt = -rc*sin(2.0*deltaTheta);
	const double deltaE = sqrt(sqr(deltaL/sl) + sqr(deltaCC/sc) + sqr(deltaHHH/sh) + rt*deltaCC/sc*deltaHHH/sh);
	return deltaE;
}
#endif


int Color::numComponents (ColorSpace colorSpace) {
	switch (colorSpace) {
		case ColorSpace::GRAY: return 1;
		case ColorSpace::LAB:
		case ColorSpace::RGB:  return 3;
		case ColorSpace::CMYK: return 4;
	}
	return 0;
}