contours.py sample added

samples/python2/contours.py

@@ -0,0 +1,48 @@
+import numpy as np
+import cv2
+
+def make_image():
+    img = np.zeros((500, 500), np.uint8)
+    black, white = 0, 255
+    for i in xrange(6):
+        dx = (i%2)*250 - 30
+        dy = (i/2)*150
+        
+        if i == 0:
+            for j in xrange(11):
+                angle = (j+5)*np.pi/21
+                c, s = np.cos(angle), np.sin(angle)
+                x1, y1 = np.int32([dx+100+j*10-80*c, dy+100-90*s])
+                x2, y2 = np.int32([dx+100+j*10-30*c, dy+100-30*s])
+                cv2.line(img, (x1, y1), (x2, y2), white)
+        
+        cv2.ellipse( img, (dx+150, dy+100), (100,70), 0, 0, 360, white, -1 )
+        cv2.ellipse( img, (dx+115, dy+70), (30,20), 0, 0, 360, black, -1 )
+        cv2.ellipse( img, (dx+185, dy+70), (30,20), 0, 0, 360, black, -1 )
+        cv2.ellipse( img, (dx+115, dy+70), (15,15), 0, 0, 360, white, -1 )
+        cv2.ellipse( img, (dx+185, dy+70), (15,15), 0, 0, 360, white, -1 )
+        cv2.ellipse( img, (dx+115, dy+70), (5,5), 0, 0, 360, black, -1 )
+        cv2.ellipse( img, (dx+185, dy+70), (5,5), 0, 0, 360, black, -1 )
+        cv2.ellipse( img, (dx+150, dy+100), (10,5), 0, 0, 360, black, -1 )
+        cv2.ellipse( img, (dx+150, dy+150), (40,10), 0, 0, 360, black, -1 )
+        cv2.ellipse( img, (dx+27, dy+100), (20,35), 0, 0, 360, white, -1 )
+        cv2.ellipse( img, (dx+273, dy+100), (20,35), 0, 0, 360, white, -1 )
+    return img
+
+if __name__ == '__main__':
+    img = make_image()
+    h, w = img.shape[:2]
+
+    contours0, hierarchy = cv2.findContours( img.copy(), cv2.RETR_TREE, cv2.CHAIN_APPROX_SIMPLE)
+    contours = [cv2.approxPolyDP(cnt, 3, True) for cnt in contours0]
+    
+    def update(levels):
+        vis = np.zeros((h, w, 3), np.uint8)
+        levels = levels - 3
+        cv2.drawContours( vis, contours, (-1, 3)[levels <= 0], (128,255,255), 
+            3, cv2.CV_AA, hierarchy, abs(levels) )
+        cv2.imshow('contours', vis)
+    update(3)
+    cv2.createTrackbar( "levels+3", "contours", 3, 7, update )
+    cv2.imshow('image', img)
+    cv2.waitKey()