A-M baby

Task/Bitmap-Midpoint-circle-algorithm/J/bitmap-midpoint-circle-algorithm-1.j

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+NB.*getBresenhamCircle v Returns points for a circle given center and radius
+NB. y is: y0 x0 radius
+getBresenhamCircle=: monad define
+  'y0 x0 radius'=. y
+  x=. 0
+  y=. radius
+  f=. -. radius
+  pts=. 0 2$0
+  while. x <: y do.
+    pts=. pts , y , x
+    if. f >: 0 do.
+      y=. <:y
+      f=. f + _2 * y
+    end.
+    x=. >:x
+    f =. f + >: 2 * x
+  end.
+  offsets=. (,|."1) (1 _1 {~ #: i.4) *"1"1 _ pts
+  ~.,/ (y0,x0) +"1 offsets
+)
+
+NB.*drawCircles v Draws circle(s) (x) on image (y)
+NB. x is: 2-item list of boxed (y0 x0 radius) ; (color)
+drawCircles=: (1&{:: ;~ [: ; [: <@getBresenhamCircle"1 (0&{::))@[ setPixels ]