outrun/pict3d-lib.rkt

#lang racket
(require pict3d)

(provide rgba-hex emitted-hex scale-number)

(define (get-hex str)
  (let*-values ([(num) (string->number str 16)]
                [(scale-n) (lambda (x) (/ x 255))]
                [(num blue) (quotient/remainder num 256)]
                [(red green) (quotient/remainder num 256)])
    (list (scale-n red) (scale-n green) (scale-n blue))))

(define (rgba-hex str [alpha 1])
  (apply rgba `(,@(get-hex str) ,alpha)))
(define (emitted-hex str intensity)
  (apply emitted `(,@(get-hex str) ,intensity)))


(define (scale-number s a1 a2 b1 b2)
  (let ([a (- a2 a1)] [b (- b2 b1)])
    (exact->inexact (+ b1 (/ (* (- s a1) b) a)))))