Data commit

Task/Bitmap-Midpoint-circle-algorithm/Racket/bitmap-midpoint-circle-algorithm.rkt

@@ -0,0 +1,43 @@
+#lang racket
+(require racket/draw)
+
+(define-syntax ⊕ (syntax-rules () [(_ id e) (set! id (+ id e))]))
+
+(define (draw-point dc x y)
+  (send dc draw-point x y))
+
+(define (draw-circle dc x0 y0 r)
+  (define f (- 1 r))
+  (define ddf_x 1)
+  (define ddf_y (* -2 r))
+  (define x 0)
+  (define y r)
+  (draw-point dc    x0    (+ y0 r))
+  (draw-point dc    x0    (- y0 r))
+  (draw-point dc (+ x0 r)    y0)
+  (draw-point dc (- x0 r)    y0)
+  (let loop ()
+    (when (< x y)
+      (when (>= f 0)
+        (⊕ y -1)
+        (⊕ ddf_y 2)
+        (⊕ f ddf_y))
+      (⊕ x 1)
+      (⊕ ddf_x 2)
+      (⊕ f ddf_x)
+      (draw-point dc (+ x0 x) (+ y0 y))
+      (draw-point dc (- x0 x) (+ y0 y))
+      (draw-point dc (+ x0 x) (- y0 y))
+      (draw-point dc (- x0 x) (- y0 y))
+      (draw-point dc (+ x0 y) (+ y0 x))
+      (draw-point dc (- x0 y) (+ y0 x))
+      (draw-point dc (+ x0 y) (- y0 x))
+      (draw-point dc (- x0 y) (- y0 x))
+      (loop))))
+
+(define bm (make-object bitmap% 25 25))
+(define dc (new bitmap-dc% [bitmap bm]))
+(send dc set-smoothing 'unsmoothed)
+(send dc set-pen "red" 1 'solid)
+(draw-circle dc 12 12 12)
+bm