python cv2 sample: coherence enhancing

samples/python2/coherence.py

+'''
+  Coherence-enhancing filtering example
+
+  inspired by  
+    Joachim Weickert "Coherence-Enhancing Shock Filters"
+    http://www.mia.uni-saarland.de/Publications/weickert-dagm03.pdf
+'''
+
+import numpy as np
+import cv, cv2
+
+
+def coherence_filter(img, sigma = 11, str_sigma = 11, blend = 0.5, iter_n = 4):
+    h, w = img.shape[:2]
+
+    for i in xrange(iter_n):
+        print i,
+        
+        gray = cv2.cvtColor(img, cv.CV_BGR2GRAY)
+        eigen = cv2.cornerEigenValsAndVecs(gray, str_sigma, 3)
+        eigen = eigen.reshape(h, w, 3, 2)  # [[e1, e2], v1, v2]
+        x, y = eigen[:,:,1,0], eigen[:,:,1,1]
+        
+        gxx = cv2.sobel(gray, cv2.CV_32F, 2, 0, ksize=sigma)
+        gxy = cv2.sobel(gray, cv2.CV_32F, 1, 1, ksize=sigma)
+        gyy = cv2.sobel(gray, cv2.CV_32F, 0, 2, ksize=sigma)
+        gvv = x*x*gxx + 2*x*y*gxy + y*y*gyy
+        m = gvv < 0
+
+        ero = cv2.erode(img, None)
+        dil = cv2.dilate(img, None)
+        img1 = ero
+        img1[m] = dil[m]
+        img = np.uint8(img*(1.0 - blend) + img1*blend)
+    print 'done'
+    return img
+
+    
+if __name__ == '__main__':
+    import sys
+    try: fn = sys.argv[1]
+    except: fn = '../cpp/baboon.jpg'
+
+    src = cv2.imread(fn)
+
+    def nothing(*argv):
+        pass
+
+    def update():
+        sigma = cv2.getTrackbarPos('sigma', 'control')*2+1
+        str_sigma = cv2.getTrackbarPos('str_sigma', 'control')*2+1
+        blend = cv2.getTrackbarPos('blend', 'control') / 10.0
+        print 'sigma: %d  str_sigma: %d  blend_coef: %f' % (sigma, str_sigma, blend)
+        dst = coherence_filter(src, sigma=sigma, str_sigma = str_sigma, blend = blend)
+        cv2.imshow('dst', dst)
+
+    cv2.namedWindow('control', 0)
+    cv.CreateTrackbar('sigma', 'control', 9, 15, nothing)
+    cv.CreateTrackbar('blend', 'control', 7, 10, nothing)
+    cv.CreateTrackbar('str_sigma', 'control', 9, 15, nothing)
+
+
+    print 'Press SPACE to update the image\n'
+
+    cv2.imshow('src', src)
+    update()
+    while True:
+        ch = cv2.waitKey()
+        if ch == ord(' '):
+            update()
+        if ch == 27:
+            break