Graphics - z80 Heaven

I got lazy in my graphics design, so I made a program to convert regular images to 4-level greyscale images in Racket. The source code is below, for anyone who cares.

#lang racket

(require picturing-programs)
(require racket/math)
(require racket/draw)

(define (draw image)
  (define (grey-function x y red green blue)
   (define n (floor (+ (* .587 green) (* .299 red) (* .114 blue))))
   (cond [(< n 42.5) 0]
         [(< n 127.5) 85]
         [(< n 212.5) 170]
         [else 255]
   ))
  (map3-image grey-function grey-function grey-function (scale .5 image)))

I scaled the images down, since the calculator screen is so small. This can be adjusted. The brightness/darkness can be adjusted by changing the 42.5, 127.5, and 212.5.

To run the program, you would need an environment (DrRacket). A bit annoying, but oh well.

I might make a similar program in Java soon.

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