Xiaolin Wu's line algorithm: Difference between revisions
{{header|Racket}} implementation added
(→{{header|Perl 6}}: add entry) |
({{header|Racket}} implementation added) |
||
Line 866:
img.save(filename)
print 'image saved to', filename</lang>
=={{header|Racket}}==
<lang racket>#lang racket
(require 2htdp/image)
(define (plot img x y c)
(define c*255 (exact-round (* (- 1 c) 255)))
(place-image
(rectangle 1 1 'solid (make-color c*255 c*255 c*255 255))
x y img))
(define ipart exact-floor) ; assume that a "round-down" is what we want when -ve
;;; `round` is built in -- but we'll use exact round (and I'm not keen on over-binding round)
(define (fpart n) (- n (exact-floor n)))
(define (rfpart n) (- 1 (fpart n)))
(define (draw-line img x0 y0 x1 y1)
(define (draw-line-steeped img x0 y0 x1 y1 steep?)
(define (draw-line-steeped-l-to-r img x0 y0 x1 y1 steep?)
(define dx (- x1 x0))
(define dy (- y1 y0))
(define gradient (/ dy dx))
(define (handle-end-point img x y)
(define xend (exact-round x))
(define yend (+ y (* gradient (- xend x))))
(define xgap (rfpart (+ x 0.5)))
(define ypxl (ipart yend))
(define intery (+ yend gradient))
(case steep?
[(#t)
(define img* (plot img ypxl xend (* xgap (rfpart yend))))
(values (plot img* (+ ypxl 1) xend (* xgap (fpart yend))) xend intery)]
[(#f)
(define img* (plot img xend ypxl (* xgap (rfpart yend))))
(values (plot img* xend (+ ypxl 1) (* xgap (fpart yend))) xend intery)]))
(define-values (img-with-l-endpoint xpl1 intery) (handle-end-point img x0 y0))
(define-values (img-with-r-endpoint xpl2 _) (handle-end-point img-with-l-endpoint x1 y1))
(for/fold ((img img-with-l-endpoint) (y intery))
((x (in-range (+ xpl1 1) xpl2)))
(define y-i (ipart y))
(values
(case steep?
[(#t)
(define img* (plot img y-i x (rfpart y)))
(plot img* (+ 1 y-i) x (fpart y))]
[(#f)
(define img* (plot img x y-i (rfpart y)))
(plot img* x (+ 1 y-i) (fpart y))])
(+ y gradient))))
(if (> x0 x1)
(draw-line-steeped-l-to-r img x1 y1 x0 y0 steep?)
(draw-line-steeped-l-to-r img x0 y0 x1 y1 steep?)))
(define steep? (> (abs (- y1 y0)) (abs (- x1 x0))))
(define-values (img* _)
(if steep?
(draw-line-steeped img y0 x0 y1 x1 steep?)
(draw-line-steeped img x0 y0 x1 y1 steep?)))
img*)
(define img-1
(beside
(scale 3 (draw-line (empty-scene 150 100) 12 12 138 88))
(above
(scale 1 (draw-line (empty-scene 150 100) 12 50 138 50))
(scale 1 (draw-line (empty-scene 150 100) 75 12 75 88))
(scale 1 (draw-line (empty-scene 150 100) 12 88 138 12)))))
(define img-2
(beside
(scale 3 (draw-line (empty-scene 100 150) 12 12 88 138))
(above (scale 1 (draw-line (empty-scene 100 150) 50 12 50 138))
(scale 1 (draw-line (empty-scene 100 150) 12 75 88 75))
(scale 1 (draw-line (empty-scene 100 150) 88 12 12 138)))))
img-1
img-2
(save-image img-1 "images/xiaolin-wu-racket-1.png")
(save-image img-2 "images/xiaolin-wu-racket-2.png")</lang>
Output files:
[[Image:xiaolin-wu-racket-1.png]]
[[Image:xiaolin-wu-racket-2.png]]
=={{header|REXX}}==
| |||