initial commit

koch.py

@@ -0,0 +1,47 @@
+#!/usr/bin/env python
+
+from __future__ import division
+try:
+    import tkinter as tk
+except:
+    import Tkinter as tk
+import math
+
+C = math.sqrt( 3 )
+
+def koch( x, y, r, smin, nmax=None ):
+    pts, tmp = [ ( x, y + r ),
+                 ( x - C * r / 2, y - r / 2 ),
+                 ( x + C * r / 2, y - r / 2 ) ], []
+    s, n = 3 * r / C, 0
+    while s > smin and ( nmax is None or n < nmax ):
+        for i in range( len( pts ) ):
+            ( x1, y1 ), ( x5, y5 ) = pts[ i - 1 ], pts[ i ]
+            dx, dy = ( x5 - x1 ) / 3, ( y5 - y1 ) / 3
+            tmp += [ ( x1 + dx, y1 + dy ),
+                     ( ( x1 + x5 + C * dy ) / 2, ( y1 + y5 - C * dx ) / 2 ),
+                     ( x5 - dx, y5 - dy ),
+                     ( x5, y5 ) ]
+        pts, tmp = tmp, []
+        s /= 4
+        n += 1
+    return pts, s, n
+
+def redraw( data ):
+    x, y = data.width / 2, data.height / 2
+    r = min( 2 * x / C, y )
+    pts, s, n = koch( x, y, r, 4, None )
+    text = "#={}\ns={:.3f}\nn={}".format( len( pts ), s, n )
+    data.widget.delete( tk.ALL )
+    data.widget.create_oval( x - r, y - r, x + r, y + r, outline="#F88" )
+    data.widget.create_text( x, y, text=text, fill="#88F", justify=tk.CENTER )
+    for i in range( len( pts ) ):
+        ( x1, y1 ), ( x2, y2 ) = pts[ i - 1 ], pts[ i ]
+        data.widget.create_line( x1, y1, x2, y2 )
+
+window = tk.Tk()
+window.title( "Koch" )
+canvas = tk.Canvas( window )
+canvas.pack( expand=True, fill=tk.BOTH )
+canvas.bind( "<Configure>", redraw )
+window.mainloop()