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304 lines
8.6 KiB
Racket
304 lines
8.6 KiB
Racket
#lang racket/base
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(require racket/contract racket/match racket/string)
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(require "named-colors.rkt")
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(module+ test (require rackunit))
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;; Conversion functions between RGB and other color systems.
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;; Adaptation of colorsys module in the Python library
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;; Original source:
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;; http://hg.python.org/cpython/file/2.7/Lib/colorsys.py
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;; References:
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;; http://en.wikipedia.org/wiki/HLS_color_space
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(provide rgb->hsl hsl->rgb
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rgb->hex hex->rgb
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hsl->hex hex->hsl)
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;; this makes things work on exact numbers by default
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(define (string->exact str)
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(string->number str 10 'number-or-false 'decimal-as-exact))
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(define unitval? (real-in 0 1))
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(define/contract (real->unitval x)
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(real? . -> . unitval?)
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(min (max 0 x) 1))
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(module+ test
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(check-equal? (real->unitval -10) 0)
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(check-equal? (real->unitval 10) 1)
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(check-equal? (real->unitval 0.5) 0.5))
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(define DEGREE_MAX 360)
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(define degree? (real-in 0 DEGREE_MAX))
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(module+ test
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(check-false (degree? -1))
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(check-true (degree? 0))
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(check-true (degree? 149.23))
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(check-true (degree? 255))
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(check-false (degree? 361)))
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;; like (modulo x 1) but works with floating-point numbers
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(define (modulo1 x)
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(- x (floor x)))
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(define/contract (unitval->byte u)
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(unitval? . -> . byte?)
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(inexact->exact (floor (* u 255))))
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(module+ test
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(check-equal? (unitval->byte 0) 0)
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(check-equal? (unitval->byte 1) 255))
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(define/contract (byte->unitval b)
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(byte? . -> . unitval?)
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(/ b 255))
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(module+ test
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(check-equal? (byte->unitval 0) 0)
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(check-equal? (byte->unitval 255) 1))
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(define (degree-string? x)
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(and (string? x) (degree? (string->exact x))))
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(define/contract (unitval->degree u)
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(unitval? . -> . degree-string?)
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(format "~a" (exact->inexact (/ (floor (* u DEGREE_MAX 100)) 100))))
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(module+ test
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(check-equal? (unitval->degree 0) "0.0")
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(check-equal? (unitval->degree 0.5) "180.0")
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(check-equal? (unitval->degree 1) "360.0"))
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(define (unitval->percentage u)
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(format "~a%" (exact->inexact (/ (floor (* u 100 100)) 100))))
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(module+ test
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(check-true (degree-string? "0"))
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(check-true (degree-string? "180"))
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(check-true (degree-string? "360"))
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(check-false (degree-string? "450"))
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(check-false (degree-string? 450))
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(check-false (degree-string? "foo")))
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(define/contract (degree-string->unitval d)
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(degree-string? . -> . unitval?)
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(/ (string->exact d) DEGREE_MAX))
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(module+ test
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(check-equal? (degree-string->unitval "0") 0)
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(check-equal? (degree-string->unitval "180") (/ 1 2))
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(check-equal? (degree-string->unitval "360") 1))
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(define/contract (trim-unitval-sign x)
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(string? . -> . string?)
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(string-trim x "%" #:left? #f))
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(module+ test
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(check-equal? (trim-unitval-sign "50") "50")
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(check-equal? (trim-unitval-sign "50%") "50")
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(check-equal? (trim-unitval-sign "%50%") "%50"))
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(define/contract (unitval-string? x)
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(any/c . -> . boolean?)
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(and (string? x)
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(equal? #\% (car (reverse (string->list x))))
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((real-in 0 100) (string->exact (trim-unitval-sign x)))))
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(module+ test
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(check-true (unitval-string? "56%"))
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(check-true (unitval-string? "0.00001%"))
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(check-false (unitval-string? 50))
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(check-false (unitval-string? "50"))
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(check-false (unitval-string? "-12%"))
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(check-false (unitval-string? "200%")))
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(define/contract (unitval-string->unitval x)
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(unitval-string? . -> . unitval?)
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(/ (string->exact (trim-unitval-sign x)) 100))
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(module+ test
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(check-equal? (unitval-string->unitval "50%") (/ 1 2))
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(check-equal? (unitval-string->unitval "100%") 1)
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(check-equal? (unitval-string->unitval "0%") 0))
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(define (trim-pound-sign x)
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(string-trim x "#" #:right? #f))
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(define (make-hex-number x)
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(string->exact (string-append "#x" (trim-pound-sign x))))
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(define HEX_DIGITS (string->list "0123456789abcdef"))
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(define (hex-digit? x)
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(member x HEX_DIGITS))
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(define (base-hex? x)
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(and (string? x)
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(equal? (substring x 0 1) "#")
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(andmap hex-digit? (string->list (string-downcase (trim-pound-sign x))))))
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(define (short-hex? x) ; like #ddd
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(and (= (string-length x) 4) (base-hex? x)))
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(define (long-hex? x) ; like #e802cf
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(and (= (string-length x) 7) (base-hex? x)))
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(define (hex? x)
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(or (short-hex? x) (long-hex? x)))
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(define rgb? (list/c unitval? unitval? unitval?))
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(define hsl? rgb?)
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(define (rgbish? x)
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(ormap (λ(proc) (proc x))
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(list
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rgb?
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(list/c unitval-string? unitval-string? unitval-string?)
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(list/c byte? byte? byte?)
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hex?
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named-color?)))
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(define/contract (rgbish->rgb x)
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(rgbish? . -> . rgb?)
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;; must handle all possible branches of rgbish
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(cond
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[(rgb? x) x]
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[((list/c unitval-string? unitval-string? unitval-string?) x)
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(map unitval-string->unitval x)]
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[((list/c byte? byte? byte?) x) (map byte->unitval x)]
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[(hex? x) (hex->rgb x)]
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[(named-color? x) (rgbish->rgb (named-color->hex x))]
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[else #f]))
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(define (hslish? x)
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(ormap (λ(proc) (proc x))
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(list
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hsl?
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(list/c degree-string? unitval-string? unitval-string?) ; aka css-hsl
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(list/c byte? byte? byte?))))
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(define (hslish->hsl x)
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(hslish? . -> . hsl?)
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(cond
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[(hsl? x) x]
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[((list/c degree-string? unitval-string? unitval-string?) x) (cons (degree-string->unitval (car x)) (map unitval-string->unitval (cdr x)))]
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[((list/c byte? byte? byte?) x) (map byte->unitval x)]
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[else #f]))
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(define (hsl->css hsl)
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(hslish? . -> . hsl?)
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(match-define (list h s lum) (hslish->hsl hsl))
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(list (unitval->degree h) (unitval->percentage s) (unitval->percentage lum)))
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;; convert rgb values into hue value
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(define/contract (rgb->h r g b)
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(unitval? unitval? unitval? . -> . unitval?)
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(define maxc (max r g b))
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(define minc (min r g b))
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(if (minc . = . maxc)
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0 ; color is gray. Return now & avoid division by zero below
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(let ()
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(define-values (rc gc bc)
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(apply values (map (λ(x) (/ (- maxc x) (- maxc minc))) (list r g b))))
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(modulo1 (/ (cond
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[(r . = . maxc) (- bc gc)]
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[(g . = . maxc) (+ 2.0 (- rc bc))]
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[else (+ 4.0 (- gc rc))])
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6.0)))))
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(define/contract (rgb->hsl rgb)
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(rgbish? . -> . hsl?)
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(match-define (list r g b) (rgbish->rgb rgb))
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(define maxc (max r g b))
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(define minc (min r g b))
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(define h (rgb->h r g b))
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(define lum (/ (+ maxc minc) 2))
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(define s (/ (- maxc minc) (if (lum . <= . 0.5)
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(+ maxc minc)
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(- 2.0 maxc minc))))
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(map real->unitval (list h s lum)))
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(define/contract (hsl->rgb hsl)
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(hslish? . -> . rgb?)
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(define ONE_THIRD (/ 1 3))
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(define ONE_SIXTH (/ 1 6))
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(define TWO_THIRDS (/ 2 3))
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(match-define (list h s lum) (hslish->hsl hsl))
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(define (_v m1 m2 hue)
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(let ([hue (modulo1 hue)])
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(cond
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[(hue . < . ONE_SIXTH) (+ m1 (* (- m2 m1) hue 6.0))]
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[(hue . < . 0.5) m2]
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[(hue . < . TWO_THIRDS) (+ m1 (* (- m2 m1) (- TWO_THIRDS hue) 6.0))]
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[else m1])))
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(define m2 (if (lum . <= . 0.5)
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(* lum (+ 1.0 s))
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(- (+ lum s) (* lum s))))
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(define m1 (- (* 2.0 lum) m2))
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(map real->unitval (map (λ(x) (_v m1 m2 x))
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(list (+ h ONE_THIRD) h (- h ONE_THIRD)))))
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(define/contract (rgb->hex rgb)
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(rgbish? . -> . hex?)
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;; make a 2-digit hex string from a number
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(define (hex-format num)
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(define hex (format "~x" num))
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(if (= (string-length hex) 1)
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(string-append "0" hex)
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hex))
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(define raw-hex (apply string-append (map hex-format (map unitval->byte (rgbish->rgb rgb)))))
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(define triple-double-pattern #px"^(\\w)\\1(\\w)\\2(\\w)\\3$")
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(define result (regexp-match triple-double-pattern raw-hex))
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(string-append "#" (if result
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; cdr result holds the three submatches
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(apply string-append (cdr result))
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raw-hex)))
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(module+ test
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(check-equal? (rgb->hex '(1 1 1)) "#fff")
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(check-equal? (rgb->hex '(0.8 0.8 0.8)) "#ccc")
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(check-equal? (rgb->hex '(0.01 0.01 0.01)) "#020202"))
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(define/contract (hex->long-hex hex)
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(hex? . -> . long-hex?)
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(if (short-hex? hex)
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(let ()
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(match-define (list d1 d2 d3) (cdr (regexp-match #px"^#(\\w)(\\w)(\\w)$" hex)))
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(string-append "#" d1 d1 d2 d2 d3 d3))
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hex))
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(define/contract (hex->rgb hex)
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(hex? . -> . rgb?)
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(let ([hex (hex->long-hex hex)])
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(define result (regexp-match #px"^#(\\w\\w)(\\w\\w)(\\w\\w)$" hex))
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(map (compose1 byte->unitval make-hex-number) (cdr result))))
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(define hsl->hex (compose1 rgb->hex hsl->rgb))
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(define hex->hsl (compose1 rgb->hsl hex->rgb)) |