# \#edge-detection **URL:** https://forum.opencv.org/tag/edge-detection/21.md [Latest](https://forum.opencv.org/latest.md) · [Categories](https://forum.opencv.org/categories.md) · [Tags](https://forum.opencv.org/tags.md) --- ## [Detecting the edges of striped fabric on a chessboard](https://forum.opencv.org/t/detecting-the-edges-of-striped-fabric-on-a-chessboard/24217)
**Author:** [@JIN\_PRO](https://forum.opencv.org/u/JIN_PRO)\ **Replies:** 7\ **Last updated:** [December 4, 2025, 7:43am UTC](https://forum.opencv.org/t/detecting-the-edges-of-striped-fabric-on-a-chessboard/24217 "2025-12-04T07:43:00Z")
When detecting striped fabric, my solution performed poorly, resulting in fragmented and incomplete detection. Here are my steps: Grayscale conversion Opening Operation: Denoising Gaussian blur Calculate the … --- ## [How to accurately segment overlapping rice grains in an image using OpenCV](https://forum.opencv.org/t/how-to-accurately-segment-overlapping-rice-grains-in-an-image-using-opencv/20618)
**Author:** [@Mary\_Joy](https://forum.opencv.org/u/Mary_Joy)\ **Replies:** 4\ **Last updated:** [May 22, 2025, 5:04pm UTC](https://forum.opencv.org/t/how-to-accurately-segment-overlapping-rice-grains-in-an-image-using-opencv/20618 "2025-05-22T17:04:31Z")
I am working on an image processing task using opencv python where I need to segment individual rice grains from an image. The challenge is that many grains are overlapping with each other. I tried watershed algorithm b… --- ## [Splitting the "G" in a Guinness - OpenCV analysis to detect point of beer line in ROI](https://forum.opencv.org/t/splitting-the-g-in-a-guinness-opencv-analysis-to-detect-point-of-beer-line-in-roi/19667)
**Author:** [@nick964](https://forum.opencv.org/u/nick964)\ **Replies:** 0\ **Last updated:** [January 2, 2025, 6:50pm UTC](https://forum.opencv.org/t/splitting-the-g-in-a-guinness-opencv-analysis-to-detect-point-of-beer-line-in-roi/19667 "2025-01-02T18:50:51Z")
I’m working on an application that will take in an image of a Guinness glass, and analyze the beer to see how successful users are in “splitting the G”. “Splitting The G” is when someone takes a full pint of Guinness, a… --- ## [Thoughts on a project](https://forum.opencv.org/t/thoughts-on-a-project/9600)
**Author:** [@svara](https://forum.opencv.org/u/svara)\ **Replies:** 0\ **Last updated:** [July 22, 2022, 10:16pm UTC](https://forum.opencv.org/t/thoughts-on-a-project/9600 "2022-07-22T22:16:18Z")
Hello, I am trying to achieve the following result using opencv and computer vision techniques. Kindly suggest me ideas on how can we possibly solve the problem: I am trying to draw curves around a circle to understand… --- ## [Extracting region with a person - CV approach](https://forum.opencv.org/t/extracting-region-with-a-person-cv-approach/10934)
**Author:** [@klutzzykitty](https://forum.opencv.org/u/klutzzykitty)\ **Replies:** 4\ **Last updated:** [November 14, 2022, 7:55am UTC](https://forum.opencv.org/t/extracting-region-with-a-person-cv-approach/10934 "2022-11-14T07:55:10Z")
What would be a better CV approach here? The goal: Extract the person or the area within (or with) the bounding box that includes the person. The object detection isn’t done by OpenCV and there isn’t any access to obje… --- ## [Edge extraction after having derivatives in x and y](https://forum.opencv.org/t/edge-extraction-after-having-derivatives-in-x-and-y/10705)
**Author:** [@MakeItGreatAgain](https://forum.opencv.org/u/MakeItGreatAgain)\ **Replies:** 5\ **Last updated:** [October 28, 2022, 12:50am UTC](https://forum.opencv.org/t/edge-extraction-after-having-derivatives-in-x-and-y/10705 "2022-10-28T00:50:49Z")
Hello, Suppose that I have already taken the derivatives in x and y of an image, dx and dy for example. How can I extract edges with dx and dy if I don’t want to use canny. Thank you. --- ## [How to detect and highlight small PCB circuit trace](https://forum.opencv.org/t/how-to-detect-and-highlight-small-pcb-circuit-trace/8661)
**Author:** [@tonytnguyenn](https://forum.opencv.org/u/tonytnguyenn)\ **Replies:** 7\ **Last updated:** [May 16, 2022, 2:11pm UTC](https://forum.opencv.org/t/how-to-detect-and-highlight-small-pcb-circuit-trace/8661 "2022-05-16T14:11:50Z")
Hi, I am trying to highlight all circuit trace in a gray-scale PCB image(attached). I’d like to highlight only the traces but not the ground pad. Can someone recommend some good approach? Thank you, --- ## [Detecting and fetching the pokemon card only](https://forum.opencv.org/t/detecting-and-fetching-the-pokemon-card-only/7555)
**Author:** [@ahmdayyy](https://forum.opencv.org/u/ahmdayyy)\ **Replies:** 1\ **Last updated:** [February 14, 2022, 10:23am UTC](https://forum.opencv.org/t/detecting-and-fetching-the-pokemon-card-only/7555 "2022-02-14T10:23:53Z")
I’ve got a pokemon card, I apply edge detection and get its edges, what I want now is to fetch the card only and calculate the length of border on pokemon card on each side. What I cannot understand is, how to fetch the … --- ## [Image dimension measurement - mm per pixel calibration](https://forum.opencv.org/t/image-dimension-measurement-mm-per-pixel-calibration/3196)
**Author:** [@RockB](https://forum.opencv.org/u/RockB)\ **Replies:** 0\ **Last updated:** [May 6, 2021, 7:39pm UTC](https://forum.opencv.org/t/image-dimension-measurement-mm-per-pixel-calibration/3196 "2021-05-06T19:39:52Z")
I am trying to measure dimension of an object in real time using a video feed from a camera. I am working off an single frame/image of the video for now. In order to measure the real (physical) dimensions, I want to fir… --- ## [Railway detection with noisy input](https://forum.opencv.org/t/railway-detection-with-noisy-input/2231)
**Author:** [@Guilherme\_Augusto](https://forum.opencv.org/u/Guilherme_Augusto)\ **Replies:** 4\ **Last updated:** [March 18, 2021, 9:24pm UTC](https://forum.opencv.org/t/railway-detection-with-noisy-input/2231 "2021-03-18T21:24:17Z")
I’m working on a railway detection algorithm with the following steps : Get the frame and turn it into grayscale. Apply Gaussian blur. Apply Sobel operator on x-axis. Apply Canny edge detector. Apply Hough-transform to…