# Contours Image Find center line **URL:** \ **Category:** C++\ **Created:** [May 16, 2022, 4:07am UTC](https://forum.opencv.org/t/contours-image-find-center-line/8794 "2022-05-16T04:07:56Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![woogusu](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.opencv.org/woogusu/32/587_2.png) [@woogusu](https://forum.opencv.org/u/woogusu)\ **Post date:** [May 16, 2022, 4:07am UTC](https://forum.opencv.org/t/contours-image-find-center-line/8794/1 "2022-05-16T04:07:56Z")
I’m trying to find a centerline in that image, what should I do? ![종이 - 복사본](https://us1.discourse-cdn.com/flex020/uploads/opencv/original/2X/f/f2d73828c6af8e31434a9ed586cdfa84084d2eee.jpeg) ---
**Author:** ![Tedxi](https://avatars.discourse-cdn.com/v4/letter/t/6bbea6/32.png) [@Tedxi](https://forum.opencv.org/u/Tedxi)\ **Post date:** [May 16, 2022, 6:11am UTC](https://forum.opencv.org/t/contours-image-find-center-line/8794/2 "2022-05-16T06:11:28Z")
what’s the meaning of ‘centerline’. If you want to detect straight lines, you can use Hough line transformation. [OpenCV: Hough Transform](https://docs.opencv.org/4.5.5/d2/d15/group __cudaimgproc__ hough.html) ---
**Author:** ![woogusu](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.opencv.org/woogusu/32/587_2.png) [@woogusu](https://forum.opencv.org/u/woogusu)\ **Post date:** [May 16, 2022, 7:03am UTC](https://forum.opencv.org/t/contours-image-find-center-line/8794/3 "2022-05-16T07:03:49Z")
I would like to find the center line and the center of the corner as shown in the image. ![그림2](https://us1.discourse-cdn.com/flex020/uploads/opencv/original/2X/a/a22cae82ce3eece2c35f40e167581ff322ea19f4.jpeg) ![그림1](https://us1.discourse-cdn.com/flex020/uploads/opencv/original/2X/5/54501b00ed1246cbec27d17f046c12d83f7cc38e.jpeg) ---
**Author:** ![pauljurczak](https://avatars.discourse-cdn.com/v4/letter/p/87869e/32.png) [@pauljurczak](https://forum.opencv.org/u/pauljurczak)\ **Post date:** [May 17, 2022, 7:24am UTC](https://forum.opencv.org/t/contours-image-find-center-line/8794/4 "2022-05-17T07:24:03Z")
Start with skeletonization ([Skeletonization in Python using OpenCV | by Neeramitra Reddy | Analytics Vidhya | Medium](https://medium.com/analytics-vidhya/skeletonization-in-python-using-opencv-b7fa16867331)), then simplify the polyline ([OpenCV Contour Approximation - PyImageSearch](https://pyimagesearch.com/2021/10/06/opencv-contour-approximation/)). ---
**Author:** ![crackwitz](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.opencv.org/crackwitz/32/14_2.png) [@crackwitz](https://forum.opencv.org/u/crackwitz)\ **Post date:** [May 17, 2022, 9:04am UTC](https://forum.opencv.org/t/contours-image-find-center-line/8794/5 "2022-05-17T09:04:18Z")
be very careful with approxPolyDP. it **does not** maintain lines, it maintains corners. if the thinning/skeleton “rounds” the corner, you’ll get lines that lie off-center. I’ve really got to implement something better than DP. commercial packages have some simple approaches that are easy to implement from nothing but looking at freely accessible advertising/sales brochures and docs. ---
**Author:** ![woogusu](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.opencv.org/woogusu/32/587_2.png) [@woogusu](https://forum.opencv.org/u/woogusu)\ **Post date:** [May 18, 2022, 12:22am UTC](https://forum.opencv.org/t/contours-image-find-center-line/8794/6 "2022-05-18T00:22:23Z")
Thank you for your help ---
**Author:** ![woogusu](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.opencv.org/woogusu/32/587_2.png) [@woogusu](https://forum.opencv.org/u/woogusu)\ **Post date:** [May 18, 2022, 12:22am UTC](https://forum.opencv.org/t/contours-image-find-center-line/8794/7 "2022-05-18T00:22:34Z")
Thank you for your help!