turing.py sample added

samples/python2/turing.py

+'''
+Multiscale Turing Patterns generator.
+Inspired by http://www.jonathanmccabe.com/Cyclic_Symmetric_Multi-Scale_Turing_Patterns.pdf
+'''
+
+import numpy as np
+import cv2, cv
+from common import draw_str
+
+w, h = 512, 512
+
+a = np.zeros((h, w, 1), np.float32)
+cv2.randu(a, np.array([0]), np.array([1]))
+a.shape = (h, w)
+
+def process_scale(a_lods, lod):
+    d = a_lods[lod] - cv2.pyrUp(a_lods[lod+1])
+    for i in xrange(lod):
+        d = cv2.pyrUp(d)
+    v = cv2.GaussianBlur(d*d, (3, 3), 0)
+    return np.sign(d), v
+    
+print 'Generating AVI file. Press ESC to stop.'
+out = cv2.VideoWriter('turing.avi', cv.CV_FOURCC(*'DIB '), 30.0, (w, h), False)
+
+scale_num = 6
+frame_num = 1000
+for frame_i in xrange(frame_num):
+    a_lods = [a]
+    for i in xrange(scale_num):
+        a_lods.append(cv2.pyrDown(a_lods[-1])) 
+    ms, vs = [], []
+    for i in xrange(1, scale_num):
+        m, v = process_scale(a_lods, i)
+        ms.append(m)
+        vs.append(v)
+    mi = np.argmin(vs, 0)
+    a += np.choose(mi, ms) * 0.025
+    a = (a-a.min()) / a.ptp()
+
+    out.write(a)
+    vis = a.copy()
+    draw_str(vis, (20, 20), 'frame %d / %d' % (frame_i+1, frame_num))
+    cv2.imshow('a', vis)
+    if cv2.waitKey(5) == 27:
+        break
+else:
+    print 'done'
+    cv2.waitKey()
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