;; (remap val '(-1 1) '(0 255))

(define (remap value source target)
  (let ((source-low (car source))
        (source-high (cadr source))
        (target-low (car target))
        (target-high (cadr target)))
    (inexact->exact (truncate (+ target-low
              (* (- target-high target-low)
                 (/ (- value source-low)
                    (- source-high source-low))))))))