2016-02-08 06:25:31 -0500 commented question Finding intersections of objects in a single contour Hello Steve, thanks for the suggestion, how do you think I could perform this first step of skeletization? Is there something useful already implemented in OpenCV? I failed to find any so far. 2016-02-04 11:48:35 -0500 received badge ● Student (source) 2016-02-04 11:44:32 -0500 asked a question Finding intersections of objects in a single contour Hello, I have an image of leaves (seen from above) that can partly recover each other. http://img11.hostingpics.net/pics/793... I found the contour of the image (in red on the image) and what I want to do now is to find where two leaves intersect. What I've done so far is to: consider a point with index i in the contour c, say c[i], which has two coordinates x and y, compute the angle of the vector (c[i-1], c[i]) with the half line (x > 0), which I denote ang[i], this returns an angle between 0 and 360, do the previous step for the B angles ang[i], ang[i-1], ang[i-2] and average the result, this gives me the mean direction before c[i], do the same for the B angles ang[i+1], ang[i+2], ang[i+3], etc. and average the result, this gives me the mean direction after c[i], flag (in blue on the image) c[i] as a potential intersection if the difference between the mean direction after and before is greater than a deviation angle D. I've tried many values of B and D, but due to the different natures of the intersections between leaves, I never manage to recover them all, and uniquely them. Here is an example of output: http://img11.hostingpics.net/pics/381... Is something wrong with the method I tried? Is there any other approach less naive and more robust I could try? Many thanks. 2016-02-04 08:07:05 -0500 received badge ● Supporter (source) 2016-02-04 08:07:02 -0500 received badge ● Scholar (source) 2016-02-04 08:07:00 -0500 commented answer Why a contour can't always be drawn filled? Forgot to reply but I tested it and it worked great, thanks a lot. 2016-02-03 10:25:46 -0500 commented question Why a contour can't always be drawn filled? I edited the question with more details. I should have done that earlier, thanks for the suggestion. 2016-02-03 10:25:00 -0500 received badge ● Editor (source) 2016-02-03 03:46:00 -0500 commented question Why a contour can't always be drawn filled? Thanks for the reply. Actually, I'm not sure I understand what you suggested. I don't really know how drawContours works internally. 2016-02-02 22:41:47 -0500 asked a question Why can't contours always be filled? Hello, I find the contours of an object, and I try to fill it with the CV_FILLED option, and sometimes (most of the time), it doesn't fill the contour, and sometimes it does (see attached pictures). What is this due to and how can I make sure that the contour be filled? Many thanks, 2016-02-02 22:41:47 -0500 asked a question Why a contour can't always be drawn filled? Hello, Sometimes when I find the contours of an image, I ask for it to be drawn with CV_FILLED, sometimes (most of the time), it doesn't fill properly the contour, but sometimes it does, why can explain this and how could I make sure it is filled everytime? In blue I plotted the first and the last Points of the contour. Many thanks Edit: A minimal code would be the following: #include "opencv2/imgproc/imgproc.hpp" #include "opencv2/highgui/highgui.hpp" using namespace cv; int main(int argc, char** argv) { int lowThreshold = 50; int max_lowThreshold = 100; int ratio = 3; int kernel_size = 3; Mat src1 = imread("/path/to/img1.jpg"); Mat src2 = imread("/path/to/img2.jpg"); Mat src_gray1; Mat src_gray2; cvtColor(src1, src_gray1, CV_BGR2GRAY); cvtColor(src2, src_gray2, CV_BGR2GRAY); Mat edge1; Mat edge2; Mat dst1; Mat dst2; Mat detected_edges1; Mat detected_edges2; std::vector > contours1, contours2; std::vector hierarchy1, hierarchy2; edge1.create(src1.size(), src1.type()); edge2.create(src2.size(), src2.type()); dst1.create(src1.size(), src1.type()); dst2.create(src2.size(), src2.type()); blur(src_gray1, detected_edges1, Size(3,3)); blur(src_gray2, detected_edges2, Size(3,3)); Canny(detected_edges1, detected_edges1, lowThreshold, lowThreshold * ratio, kernel_size); Canny(detected_edges2, detected_edges2, lowThreshold, lowThreshold * ratio, kernel_size); findContours(detected_edges1, contours1, hierarchy1, CV_RETR_EXTERNAL, CV_CHAIN_APPROX_SIMPLE); findContours(detected_edges2, contours2, hierarchy2, CV_RETR_EXTERNAL, CV_CHAIN_APPROX_SIMPLE); drawContours(edge1, contours1, 0, Scalar(0, 0, 255), CV_FILLED, 8, hierarchy1); drawContours(edge2, contours2, 0, Scalar(0, 0, 255), CV_FILLED, 8, hierarchy2); imwrite("result1.jpg", edge1); imwrite("result2.jpg", edge2); return 0; }  where the files "img1.jpg" and "img2.jpg" can be downloaded from here: http://hpics.li/ecb8b7a http://hpics.li/f1672f0