Hi,
When my program call convexityDefects with a contour which is a line or a point an exception is thrown at in convHull.cpp. I understand that for a line or a point there is no defect so may be it is better to send an empty vector<vec4i>.
Is it correct?
../../../modules/imgproc/src/convhull.cpp:279 error (-215) hpoints>2 in function cv::convexityDefects
With image givenmy program is here
There is no convexity to be computed if the contour has not at least 3 points (so it may be a polygon)... I consider that the function is ok, you should filter those contours that may not be polygons
As you see, the problem is in convhull. A hull cannot be computed for a non-polygon contour, that is why I said that it is correct and you shall do the filter of 1 ad 2 points contours. The function is computing first the convex hull and then it determines the defects, so an exception is thrown in case of non-polygon contour
Problem is for contour 6 which have four points : point 0 (65,39), point 1(66,39), point 2 (67,39), point 3 (66,39) ConvexHull is 2 and 0.
No for contours 1 it'sonly one point in (258,71) convexHull is only point 0. Here there is no exception. it is processed at this line.
It seems so that problem occurs when there is a contour with 4 points and only two points in convex Hull
The problem seems to be in the hull, the 4 points contour cannot have 2 points convexHull. Are you sure that it is the right hull? IMHO the hull shall has at least 3 points. Anyway, have you tried to do some erode+dilate for removing the small contours?
There is no polygon with less than 3 corners... as wikipedia says it, too, the monogon and digon are "Not generally recognised as a polygon". So you should filter those out. On the other hand I had not time to test your code, probably I'll do it this weekend.
Asked: 2015-09-22 08:37:00 -0600
Seen: 1,072 times
Last updated: Sep 24 '15
What is the exception?