/usr/share/slib/colorspc.scm is in slib 3b1-4.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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 | ;;; "colorspc.scm" color-space conversions
;Copyright 2001, 2002 Aubrey Jaffer
;
;Permission to copy this software, to modify it, to redistribute it,
;to distribute modified versions, and to use it for any purpose is
;granted, subject to the following restrictions and understandings.
;
;1. Any copy made of this software must include this copyright notice
;in full.
;
;2. I have made no warranty or representation that the operation of
;this software will be error-free, and I am under no obligation to
;provide any services, by way of maintenance, update, or otherwise.
;
;3. In conjunction with products arising from the use of this
;material, there shall be no use of my name in any advertising,
;promotional, or sales literature without prior written consent in
;each case.
(require 'logical)
(require 'multiarg/and-)
(require-if 'compiling 'sort)
(require-if 'compiling 'ciexyz)
;@
(define (color:linear-transform matrix row)
(map (lambda (mrow) (apply + (map * mrow row)))
matrix))
(define RGB709:into-matrix
'(( 3.240479 -1.537150 -0.498535 )
( -0.969256 1.875992 0.041556 )
( 0.055648 -0.204043 1.057311 )))
;;; http://www.pima.net/standards/it10/PIMA7667/PIMA7667-2001.PDF gives
;;; matrix identical to sRGB:from-matrix, but colors drift under
;;; repeated conversions to and from CIEXYZ. Instead use RGB709.
(define RGB709:from-matrix
'(( 0.412453 0.357580 0.180423 )
( 0.212671 0.715160 0.072169 )
( 0.019334 0.119193 0.950227 )))
;; From http://www.cs.rit.edu/~ncs/color/t_convert.html
;@
(define (CIEXYZ->RGB709 XYZ)
(color:linear-transform RGB709:into-matrix XYZ))
(define (RGB709->CIEXYZ rgb)
(color:linear-transform RGB709:from-matrix rgb))
;;; From http://www.w3.org/Graphics/Color/sRGB.html
(define sRGB-log
(lambda (sv)
(if (<= sv 0.00304)
(* 12.92 sv)
(+ -0.055 (* 1.055 (expt sv 10/24))))))
(define sRGB-exp
(lambda (x)
(if (<= x 0.03928)
(/ x 12.92)
(expt (/ (+ 0.055 x) 1.055) 2.4))))
;; Clipping as recommended by sRGB spec.
;@
(define (CIEXYZ->sRGB XYZ)
(map (lambda (sv)
(inexact->exact (round (* 255 (sRGB-log (max 0 (min 1 sv)))))))
(color:linear-transform RGB709:into-matrix XYZ)))
(define (sRGB->CIEXYZ sRGB)
(color:linear-transform
RGB709:from-matrix
(map sRGB-exp
(map (lambda (b8v) (/ b8v 255.0)) sRGB))))
;;; sRGB values are sometimes written as 24-bit integers 0xRRGGBB
;@
(define (xRGB->sRGB xRGB)
(list (ash xRGB -16)
(logand (ash xRGB -8) 255)
(logand xRGB 255)))
(define (sRGB->xRGB sRGB)
(apply + (map * sRGB '(#x10000 #x100 #x1))))
;@
(define (xRGB->CIEXYZ xRGB) (sRGB->CIEXYZ (xRGB->sRGB xRGB)))
(define (CIEXYZ->xRGB xyz) (sRGB->xRGB (CIEXYZ->sRGB xyz)))
;;; http://www.pima.net/standards/it10/PIMA7667/PIMA7667-2001.PDF
;;; Photography - Electronic still picture imaging -
;;; Extended sRGB color encoding - e-sRGB
(define e-sRGB-log
(lambda (sv)
(cond ((< sv -0.0031308)
(- 0.055 (* 1.055 (expt (- sv) 10/24))))
((<= sv 0.0031308)
(* 12.92 sv))
(else (+ -0.055 (* 1.055 (expt sv 10/24)))))))
(define e-sRGB-exp
(lambda (x)
(cond ((< x -0.04045)
(- (expt (/ (- 0.055 x) 1.055) 2.4)))
((<= x 0.04045)
(/ x 12.92))
(else (expt (/ (+ 0.055 x) 1.055) 2.4)))))
;@
(define (CIEXYZ->e-sRGB n XYZ)
(define two^n-9 (ash 1 (- n 9)))
(define offset (* 3 (ash 1 (- n 3))))
(map (lambda (x)
(+ (inexact->exact (round (* x 255 two^n-9))) offset))
(map e-sRGB-log
(color:linear-transform
RGB709:into-matrix
XYZ))))
;@
(define (e-sRGB->CIEXYZ n rgb)
(define two^n-9 (ash 1 (- n 9)))
(define offset (* 3 (ash 1 (- n 3))))
(color:linear-transform
RGB709:from-matrix
(map e-sRGB-exp
(map (lambda (b8v) (/ (- b8v offset) 255.0 two^n-9))
rgb))))
;@
(define (sRGB->e-sRGB n sRGB)
(define two^n-9 (ash 1 (- n 9)))
(define offset (* 3 (ash 1 (- n 3))))
(map (lambda (x) (+ offset (* two^n-9 x))) sRGB))
;@
(define (e-sRGB->sRGB n rgb)
(define two^n-9 (ash 1 (- n 9)))
(define offset (* 3 (ash 1 (- n 3))))
(map (lambda (x) (/ (- x offset) two^n-9)) rgb))
;@
(define (e-sRGB->e-sRGB n rgb m)
(define shft (- m n))
(cond ((zero? shft) rgb)
(else (map (lambda (x) (ash x shft)) rgb))))
;;; From http://www.cs.rit.edu/~ncs/color/t_convert.html
;;; CIE 1976 L*a*b* is based directly on CIE XYZ and is an attampt to
;;; linearize the perceptibility of color differences. The non-linear
;;; relations for L*, a*, and b* are intended to mimic the logarithmic
;;; response of the eye. Coloring information is referred to the color
;;; of the white point of the system, subscript n.
;;;; L* is CIE lightness
;;; L* = 116 * (Y/Yn)^1/3 - 16 for Y/Yn > 0.008856
;;; L* = 903.3 * Y/Yn otherwise
(define (CIE:Y/Yn->L* Y/Yn)
(if (> Y/Yn 0.008856)
(+ -16 (* 116 (expt Y/Yn 1/3)))
(* 903.3 Y/Yn)))
(define (CIE:L*->Y/Yn L*)
(cond ((<= L* (* 903.3 0.008856))
(/ L* 903.3))
((<= L* 100.)
(expt (/ (+ L* 16) 116) 3))
(else 1)))
;;; a* = 500 * ( f(X/Xn) - f(Y/Yn) )
;;; b* = 200 * ( f(Y/Yn) - f(Z/Zn) )
;;; where f(t) = t^1/3 for t > 0.008856
;;; f(t) = 7.787 * t + 16/116 otherwise
(define (ab-log t)
(if (> t 0.008856)
(expt t 1/3)
(+ 16/116 (* t 7.787))))
(define (ab-exp f)
(define f3 (expt f 3))
(if (> f3 0.008856)
f3
(/ (- f 16/116) 7.787)))
;@
(define (CIEXYZ->L*a*b* XYZ . white-point)
(apply (lambda (X/Xn Y/Yn Z/Zn)
(list (CIE:Y/Yn->L* Y/Yn)
(* 500 (- (ab-log X/Xn) (ab-log Y/Yn)))
(* 200 (- (ab-log Y/Yn) (ab-log Z/Zn)))))
(map / XYZ (if (null? white-point)
CIEXYZ:D65
(car white-point)))))
;;; Here Xn, Yn and Zn are the tristimulus values of the reference white.
;@
(define (L*a*b*->CIEXYZ L*a*b* . white-point)
(apply (lambda (Xn Yn Zn)
(apply (lambda (L* a* b*)
(let* ((Y/Yn (CIE:L*->Y/Yn L*))
(fY/Yn (ab-log Y/Yn)))
(list (* Xn (ab-exp (+ fY/Yn (/ a* 500))))
(* Yn Y/Yn)
(* Zn (ab-exp (+ fY/Yn (/ b* -200)))))))
L*a*b*))
(if (null? white-point)
CIEXYZ:D65
(car white-point))))
;;; XYZ to CIELUV
;;; CIE 1976 L*u*u* (CIELUV) is based directly on CIE XYZ and is another
;;; attampt to linearize the perceptibility of color differences. L* is
;;; CIE lightness as for L*a*b* above. The non-linear relations for u*
;;; and v* are:
;;; u* = 13 L* ( u' - un' )
;;; v* = 13 L* ( v' - vn' )
;;; The quantities un' and vn' refer to the reference white or the light
;;; source; for the 2.o observer and illuminant C, un' = 0.2009, vn' =
;;; 0.4610. Equations for u' and v' are given below:
;;; u' = 4 X / (X + 15 Y + 3 Z)
;;; v' = 9 Y / (X + 15 Y + 3 Z)
(define (XYZ->uv XYZ)
(apply (lambda (X Y Z)
(define denom (+ X (* 15 Y) (* 3 Z)))
(if (zero? denom)
'(4. 9.)
(list (/ (* 4 X) denom)
(/ (* 9 Y) denom))))
XYZ))
;@
(define (CIEXYZ->L*u*v* XYZ . white-point)
(set! white-point (if (null? white-point)
CIEXYZ:D65
(car white-point)))
(let* ((Y/Yn (/ (cadr XYZ) (cadr white-point)))
(L* (CIE:Y/Yn->L* Y/Yn)))
(cons L* (map (lambda (q) (* 13 L* q))
(map - (XYZ->uv XYZ) (XYZ->uv white-point))))))
;;; CIELUV to XYZ
;;; The transformation from CIELUV to XYZ is performed as following:
;;; u' = u / ( 13 L* ) + un
;;; v' = v / ( 13 L* ) + vn
;;; X = 9 Y u' / 4 v'
;;; Z = ( 12 Y - 3 Y u' - 20 Y v' ) / 4 v'
;@
(define (L*u*v*->CIEXYZ L*u*v* . white-point)
(set! white-point (if (null? white-point)
CIEXYZ:D65
(car white-point)))
(apply (lambda (un vn)
(apply (lambda (L* u* v*)
(if (not (positive? L*))
'(0. 0. 0.)
(let* ((up (+ (/ u* 13 L*) un))
(vp (+ (/ v* 13 L*) vn))
(Y (* (CIE:L*->Y/Yn L*) (cadr white-point))))
(list (/ (* 9 Y up) 4 vp)
Y
(/ (* Y (+ 12 (* -3 up) (* -20 vp))) 4 vp)))))
L*u*v*))
(XYZ->uv white-point)))
;;; http://www.inforamp.net/~poynton/PDFs/coloureq.pdf
(define pi (* 4 (atan 1)))
(define pi/180 (/ pi 180))
;@
(define (L*a*b*->L*C*h lab)
(define h (/ (atan (caddr lab) (cadr lab)) pi/180))
(list (car lab)
(sqrt (apply + (map * (cdr lab) (cdr lab))))
(if (negative? h) (+ 360 h) h)))
;@
(define (L*C*h->L*a*b* lch)
(apply (lambda (L* C* h)
(set! h (* h pi/180))
(list L*
(* C* (cos h))
(* C* (sin h))))
lch))
;@
(define (L*a*b*:DE* lab1 lab2)
(sqrt (apply + (map (lambda (x) (* x x)) (map - lab1 lab2)))))
;;; http://www.colorpro.com/info/data/cie94.html
(define (color:process-params parametric-factors)
(define ans
(case (length parametric-factors)
((0) #f)
((1) (if (list? parametric-factors)
(apply color:process-params parametric-factors)
(append parametric-factors '(1 1))))
((2) (append parametric-factors '(1)))
((3) parametric-factors)
(else (slib:error 'parametric-factors 'too-many parametric-factors))))
(and ans
(for-each (lambda (obj)
(if (not (number? obj))
(slib:error 'parametric-factors 'not 'number? obj)))
ans))
ans)
;@
(define (L*C*h:DE*94 lch1 lch2 . parametric-factors)
(define C* (sqrt (* (cadr lch1) (cadr lch2)))) ;Geometric mean
(sqrt (apply + (map /
(map (lambda (x) (* x x)) (map - lch1 lch2))
(list 1 ; S_l
(+ 1 (* .045 C*)) ; S_c
(+ 1 (* .015 C*))) ; S_h
(or (color:process-params parametric-factors)
'(1 1 1))))))
;;; CMC-DE is designed only for small color-differences. But try to do
;;; something reasonable for large differences. Use bisector (h*) of
;;; the hue angles if separated by less than 90.o; otherwise, pick h of
;;; the color with larger C*.
;@
(define (CMC-DE lch1 lch2 . parametric-factors)
(apply (lambda (L* C* h_) ;Geometric means
(let ((ang1 (* pi/180 (caddr lch1)))
(ang2 (* pi/180 (caddr lch2))))
(cond ((>= 90 (abs (/ (atan (sin (- ang1 ang2))
(cos (- ang1 ang2)))
pi/180)))
(set! h_ (/ (atan (+ (sin ang1) (sin ang2))
(+ (cos ang1) (cos ang2)))
pi/180)))
((>= (cadr lch1) (cadr lch2)) (caddr lch1))
(else (caddr lch2))))
(let* ((C*^4 (expt C* 4))
(f (sqrt (/ C*^4 (+ C*^4 1900))))
(T (if (and (> h_ 164) (< h_ 345))
(+ 0.56 (abs (* 0.2 (cos (* (+ h_ 168) pi/180)))))
(+ 0.36 (abs (* 0.4 (cos (* (+ h_ 35) pi/180)))))))
(S_l (if (< L* 16)
0.511
(/ (* 0.040975 L*) (+ 1 (* 0.01765 L*)))))
(S_c (+ (/ (* 0.0638 C*) (+ 1 (* 0.0131 C*))) 0.638))
(S_h (* S_c (+ (* (+ -1 T) f) 1))))
(sqrt (apply
+ (map /
(map (lambda (x) (* x x)) (map - lch1 lch2))
(list S_l S_c S_h)
(or (color:process-params parametric-factors)
'(2 1 1)))))))
(map sqrt (map * lch1 lch2))))
;;; Chromaticity
;@
(define (XYZ->chromaticity XYZ)
(define sum (apply + XYZ))
(list (/ (car XYZ) sum) (/ (cadr XYZ) sum)))
;@
(define (chromaticity->CIEXYZ x y)
(list x y (- 1 x y)))
(define (chromaticity->whitepoint x y)
(list (/ x y) 1 (/ (- 1 x y) y)))
;@
(define (XYZ->xyY XYZ)
(define sum (apply + XYZ))
(if (zero? sum)
'(0 0 0)
(list (/ (car XYZ) sum) (/ (cadr XYZ) sum) (cadr XYZ))))
;@
(define (xyY->XYZ xyY)
(define x (car xyY))
(define y (cadr xyY))
(if (zero? y)
'(0 0 0)
(let ((Y/y (/ (caddr xyY) y)))
(list (* Y/y x) (caddr xyY) (* Y/y (- 1 x y))))))
;@
(define (xyY:normalize-colors lst . n)
(define (nthcdr n lst) (if (zero? n) lst (nthcdr (+ -1 n) (cdr lst))))
(define Ys (map caddr lst))
(set! n (if (null? n) 1 (car n)))
(let ((max-Y (if (positive? n)
(* n (apply max Ys))
(let ()
(require 'sort)
(apply max (nthcdr (- n) (sort Ys >=)))))))
(map (lambda (xyY)
(let ((x (max 0 (car xyY)))
(y (max 0 (cadr xyY))))
(define sum (max 1 (+ x y)))
(list (/ x sum)
(/ y sum)
(max 0 (min 1 (/ (caddr xyY) max-Y))))))
lst)))
;;; http://www.aim-dtp.net/aim/technology/cie_xyz/cie_xyz.htm:
;;; Illuminant D65 0.312713 0.329016
;; (define CIEXYZ:D65 (chromaticity->whitepoint 0.312713 0.329016))
;; (define CIEXYZ:D65 (chromaticity->whitepoint 0.3127 0.3290))
;@
(define CIEXYZ:D50 (chromaticity->whitepoint 0.3457 0.3585))
;;; With its 16-bit resolution, e-sRGB-16 is extremely sensitive to
;;; whitepoint. Even the 6 digits of precision specified above is
;;; insufficient to make (color->e-srgb 16 d65) ==> (57216 57216 57216)
;@
(define CIEXYZ:D65 (e-sRGB->CIEXYZ 16 '(57216 57216 57216)))
;;; http://www.efg2.com/Lab/Graphics/Colors/Chromaticity.htm CIE 1931:
;@
(define CIEXYZ:A (chromaticity->whitepoint 0.44757 0.40745)) ; 2856.K
(define CIEXYZ:B (chromaticity->whitepoint 0.34842 0.35161)) ; 4874.K
(define CIEXYZ:C (chromaticity->whitepoint 0.31006 0.31616)) ; 6774.K
(define CIEXYZ:E (chromaticity->whitepoint 1/3 1/3)) ; 5400.K
;;; Converting spectra
(define cie:x-bar #f)
(define cie:y-bar #f)
(define cie:z-bar #f)
;@
(define (load-ciexyz . path)
(let ((path (if (null? path)
(in-vicinity (library-vicinity) "cie1931.xyz")
(car path))))
(set! cie:x-bar (make-vector 80))
(set! cie:y-bar (make-vector 80))
(set! cie:z-bar (make-vector 80))
(call-with-input-file path
(lambda (iprt)
(do ((wlen 380 (+ 5 wlen))
(idx 0 (+ 1 idx)))
((>= wlen 780))
(let ((rlen (read iprt)))
(if (not (eqv? wlen rlen))
(slib:error path 'expected wlen 'not rlen))
(vector-set! cie:x-bar idx (read iprt))
(vector-set! cie:y-bar idx (read iprt))
(vector-set! cie:z-bar idx (read iprt))))))))
;@
(define (read-cie-illuminant path)
(define siv (make-vector 107))
(call-with-input-file path
(lambda (iprt)
(do ((idx 0 (+ 1 idx)))
((>= idx 107) siv)
(vector-set! siv idx (read iprt))))))
;@
(define (read-normalized-illuminant path)
(define siv (read-cie-illuminant path))
(let ((yw (/ (cadr (spectrum->XYZ siv 300e-9 830e-9)))))
(illuminant-map (lambda (w x) (* x yw)) siv)))
;@
(define (illuminant-map proc siv)
(define prod (make-vector 107))
(do ((idx 106 (+ -1 idx))
(w 830e-9 (+ -5e-9 w)))
((negative? idx) prod)
(vector-set! prod idx (proc w (vector-ref siv idx)))))
;@
(define (illuminant-map->XYZ proc siv)
(spectrum->XYZ (illuminant-map proc siv) 300e-9 830e-9))
;@
(define (wavelength->XYZ wl)
(if (not cie:y-bar) (require 'ciexyz))
(set! wl (- (/ wl 5.e-9) 380/5))
(if (<= 0 wl (+ -1 400/5))
(let* ((wlf (inexact->exact (floor wl)))
(res (- wl wlf)))
(define (interpolate vect idx res)
(+ (* res (vector-ref vect idx))
(* (- 1 res) (vector-ref vect (+ 1 idx)))))
(list (interpolate cie:x-bar wlf res)
(interpolate cie:y-bar wlf res)
(interpolate cie:z-bar wlf res)))
(slib:error 'wavelength->XYZ 'out-of-range wl)))
(define (wavelength->chromaticity wl)
(XYZ->chromaticity (wavelength->XYZ wl)))
;@
(define (spectrum->XYZ . args)
(define x 0)
(define y 0)
(define z 0)
(if (not cie:y-bar) (require 'ciexyz))
(case (length args)
((1)
(set! args (car args))
(do ((wvln 380.e-9 (+ 5.e-9 wvln))
(idx 0 (+ 1 idx)))
((>= idx 80) (map (lambda (x) (/ x 80)) (list x y z)))
(let ((inten (args wvln)))
(set! x (+ x (* (vector-ref cie:x-bar idx) inten)))
(set! y (+ y (* (vector-ref cie:y-bar idx) inten)))
(set! z (+ z (* (vector-ref cie:z-bar idx) inten))))))
((3)
(let* ((vect (if (list? (car args)) (list->vector (car args)) (car args)))
(vlen (vector-length vect))
(x1 (cadr args))
(x2 (caddr args))
(xinc (/ (- x2 x1) (+ -1 vlen)))
(x->j (lambda (x) (inexact->exact (round (/ (- x x1) xinc)))))
(x->k (lambda (x) (inexact->exact (round (/ (- x 380.e-9) 5.e-9)))))
(j->x (lambda (j) (+ x1 (* j xinc))))
(k->x (lambda (k) (+ 380.e-9 (* k 5.e-9))))
(xlo (max (min x1 x2) 380.e-9))
(xhi (min (max x1 x2) 780.e-9))
(jhi (x->j xhi))
(khi (x->k xhi))
(jinc (if (negative? xinc) -1 1)))
(if (<= (abs xinc) 5.e-9)
(do ((wvln (j->x (x->j xlo)) (+ wvln (abs xinc)))
(jdx (x->j xlo) (+ jdx jinc)))
((>= jdx jhi)
(let ((nsmps (abs (- jhi (x->j xlo)))))
(map (lambda (x) (/ x nsmps)) (list x y z))))
(let ((ciedex (min 79 (x->k wvln)))
(inten (vector-ref vect jdx)))
(set! x (+ x (* (vector-ref cie:x-bar ciedex) inten)))
(set! y (+ y (* (vector-ref cie:y-bar ciedex) inten)))
(set! z (+ z (* (vector-ref cie:z-bar ciedex) inten)))))
(do ((wvln (k->x (x->k xlo)) (+ wvln 5.e-9))
(kdx (x->k xlo) (+ kdx 1)))
((>= kdx khi)
(let ((nsmps (abs (- khi (x->k xlo)))))
(map (lambda (x) (/ x nsmps)) (list x y z))))
(let ((inten (vector-ref vect (x->j wvln))))
(set! x (+ x (* (vector-ref cie:x-bar kdx) inten)))
(set! y (+ y (* (vector-ref cie:y-bar kdx) inten)))
(set! z (+ z (* (vector-ref cie:z-bar kdx) inten))))))))
(else (slib:error 'spectrum->XYZ 'wna args))))
(define (spectrum->chromaticity . args)
(XYZ->chromaticity (apply spectrum->XYZ args)))
;@
(define blackbody-spectrum
(let* ((c 2.998e8)
(h 6.626e-34)
(h*c (* h c))
(k 1.381e-23)
(pi*2*h*c*c (* 2 pi h*c c)))
(lambda (temp . span)
(define h*c/kT (/ h*c k temp))
(define pi*2*h*c*c*span
(* pi*2*h*c*c (if (null? span) 1.e-9 (car span))))
(lambda (x)
(/ pi*2*h*c*c*span
(expt x 5)
(- (exp (/ h*c/kT x)) 1))))))
;@
(define (temperature->XYZ temp . span)
(spectrum->XYZ (apply blackbody-spectrum temp span))) ;was .5e-9
(define (temperature->chromaticity temp)
(XYZ->chromaticity (temperature->XYZ temp)))
|