work on demo.py shell

samples/python2/edge.py

@@ -2,28 +2,29 @@ import cv2
 import video
 import sys
 
-try: fn = sys.argv[1]
-except: fn = video.presets['chess']
+if __name__ == '__main__':
+    try: fn = sys.argv[1]
+    except: fn = video.presets['chess']
 
-def nothing(*arg):
-    pass
+    def nothing(*arg):
+        pass
 
-cv2.namedWindow('edge')
-cv2.createTrackbar('thrs1', 'edge', 2000, 5000, nothing)
-cv2.createTrackbar('thrs2', 'edge', 4000, 5000, nothing)
+    cv2.namedWindow('edge')
+    cv2.createTrackbar('thrs1', 'edge', 2000, 5000, nothing)
+    cv2.createTrackbar('thrs2', 'edge', 4000, 5000, nothing)
 
-cap = video.create_capture(fn)
-while True:
-    flag, img = cap.read()
-    gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
-    thrs1 = cv2.getTrackbarPos('thrs1', 'edge')
-    thrs2 = cv2.getTrackbarPos('thrs2', 'edge')
-    edge = cv2.Canny(gray, thrs1, thrs2, apertureSize=5)
-    vis = img.copy()
-    vis /= 2
-    vis[edge != 0] = (0, 255, 0)
-    cv2.imshow('edge', vis)
-    ch = cv2.waitKey(5)
-    if ch == 27:
-        break
+    cap = video.create_capture(fn)
+    while True:
+        flag, img = cap.read()
+        gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
+        thrs1 = cv2.getTrackbarPos('thrs1', 'edge')
+        thrs2 = cv2.getTrackbarPos('thrs2', 'edge')
+        edge = cv2.Canny(gray, thrs1, thrs2, apertureSize=5)
+        vis = img.copy()
+        vis /= 2
+        vis[edge != 0] = (0, 255, 0)
+        cv2.imshow('edge', vis)
+        ch = cv2.waitKey(5)
+        if ch == 27:
+            break