Merge pull request #6812 from aleksandaratanasov:master

samples/python/houghcircles.py

@@ -29,11 +29,14 @@ if __name__ == '__main__':
     cimg = src.copy() # numpy function
 
     circles = cv2.HoughCircles(img, cv2.HOUGH_GRADIENT, 1, 10, np.array([]), 100, 30, 1, 30)
-    a, b, c = circles.shape
-    for i in range(b):
-        cv2.circle(cimg, (circles[0][i][0], circles[0][i][1]), circles[0][i][2], (0, 0, 255), 3, cv2.LINE_AA)
-        cv2.circle(cimg, (circles[0][i][0], circles[0][i][1]), 2, (0, 255, 0), 3, cv2.LINE_AA)  # draw center of circle
+
+    if circles != None: # Check if circles have been found and only then iterate over these and add them to the image
+        a, b, c = circles.shape
+        for i in range(b):
+            cv2.circle(cimg, (circles[0][i][0], circles[0][i][1]), circles[0][i][2], (0, 0, 255), 3, cv2.LINE_AA)
+            cv2.circle(cimg, (circles[0][i][0], circles[0][i][1]), 2, (0, 255, 0), 3, cv2.LINE_AA)  # draw center of circle
+
+        cv2.imshow("detected circles", cimg)
 
     cv2.imshow("source", src)
-    cv2.imshow("detected circles", cimg)
     cv2.waitKey(0)

samples/python/houghlines.py

@@ -36,17 +36,19 @@ if __name__ == '__main__':
 
     else:    # HoughLines
         lines = cv2.HoughLines(dst, 1, math.pi/180.0, 50, np.array([]), 0, 0)
-        a,b,c = lines.shape
-        for i in range(a):
-            rho = lines[i][0][0]
-            theta = lines[i][0][1]
-            a = math.cos(theta)
-            b = math.sin(theta)
-            x0, y0 = a*rho, b*rho
-            pt1 = ( int(x0+1000*(-b)), int(y0+1000*(a)) )
-            pt2 = ( int(x0-1000*(-b)), int(y0-1000*(a)) )
-            cv2.line(cdst, pt1, pt2, (0, 0, 255), 3, cv2.LINE_AA)
+        if lines != None:
+            a,b,c = lines.shape
+            for i in range(a):
+                rho = lines[i][0][0]
+                theta = lines[i][0][1]
+                a = math.cos(theta)
+                b = math.sin(theta)
+                x0, y0 = a*rho, b*rho
+                pt1 = ( int(x0+1000*(-b)), int(y0+1000*(a)) )
+                pt2 = ( int(x0-1000*(-b)), int(y0-1000*(a)) )
+                cv2.line(cdst, pt1, pt2, (0, 0, 255), 3, cv2.LINE_AA)
+
+            cv2.imshow("detected lines", cdst)
 
     cv2.imshow("source", src)
-    cv2.imshow("detected lines", cdst)
     cv2.waitKey(0)