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Questions tagged [edge-detection]

Edge detection is a tool in computer vision used to find discontinuities (edges) in images or graphs. Use this tag when asking about finding and manipulating edges or edge interaction.

Edge detection is a part of computer vision where the goal is to find edges in images. This often involves computing derivatives of the image with respect to the coordinates, because intuitively if the difference between two neighboring pixels is high, it is likely that there is an edge in the image. A popular edge detection algorithm is the Canny edge detector. Other edge detection algorithm includes Laplace & Sobel.

Discontinuities in image are likely to correspond to

  • discontinuities in depth
  • discontinuities in surface orientation
  • changes in material properties and
  • variations in scene illumination
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To find minute circles using hough circle function in opencv for iris

I need to detect the iris of the eye picture I have using HoughCircle function thats available in opencv2. So , // Read the image src = imread("D:/001R_3.png"); if( !src.data ) { return -1; } /// Convert it to gray …
Aps18
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GPUImage CannyEdgeDetectionFilter with white edges?

I'm using GPUImage from the Git repository to apply some filters to images. I notice that the edge detection filters (I'm using the CannyEdgeDetectionFilter specifically) paint white edges on black background. Anyone know how to make that black…
Tony
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Given normal map in world space what is a suitable algorithm to find edges?

If I have the vertex normals of a normal scene showing up as colours in a texture in world space is there a way to calculate edges efficiently or is it mathematically impossible? I know it's possible to calculate edges if you have the normals in…
meds
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Background Extraction in MATLAB

I am working on a project in MATLAB which will extract background from an image, like if this is an image it should give me locations/coordinates of background(blue part) or person's image, so far I have calculated 1) edges using canny 2) connected…
Muaz Usmani
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Minimum threshold in Matlab Canny edge detector

Matlab Version : 7.8.0(R2009a) I am using Canny edge detector in Matlab to find the edges, But for my problem, I need some X amount of edges. I need more no. of edges then it is returned by setting threshold as 0. For example in the below image :…
Mangat Rai Modi
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Edge detection : Any performance evaluation technique?

I am working on edge detection in images and would like to evaluate the performance of algorithm, if any any one could give me a reference or method on how to proceed it will be really helpful. :) I do not have ground truth and data set includes…
DBS
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cv::Canny throws mismatched/unsupported formats exception

I'm doing some pretty basic edge detection stuff. Part of my implementation involves copying from a custom Image class to a cv::Mat and then copying back to an Image. I'm working with this article as my guide for getting the edge detection and…
OEP
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Edge with threshold bar

I am currently creating a program which manipulates and changes pixel values within black and white images. I am using Microsoft Visual Studio 2010. So far i have created edge detection using roberts gradient, Firstly i created this without a track…
user1081326
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Line detection using PIL

Given an image consisting of black lines (a few pixels wide) on white background, what is a good way to find the coordinates along the the lines, say for every 10th pixel or so? I am considering using PIL for the task, but other python or java-based…
Roar Skullestad
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Roundess in Matlab

I have this code for calculating roundess I = imread('http://energyfanatics.com/wp-content/uploads/2008/05/banana.jpg'); %I = imread('http://www.nyapplecountry.com/images/photosvarieties/redrome04.jpg'); pic = rgb2gray(I); threshold =…
2thecore
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Text detection using connected component labeling

I'm creating a project where I have to detect text regions in an image and localize text lines. This I have not yet implemented, in this project after the initial image pre-processing I will generate an edge map and then use CCL (two-pass algorithm)…
user1593832
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C# paint image within edges

I am developing an application which aids users to paint effectively. I have a C# code which runs a matlab script and gets the edge detected black and white image of a reference image. Now, I have developed the code which can allow the user to paint…
Bharath
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BoxDetection Algorithm

I am looking for guidance making a program in C# that take in a bunch of bmp images and detects a box on the image and returns the cropped box as a bmp image in a separate folder. I am using Visual Basic 2010. I have looked into all the different…
Tom P
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Python OpenCv gives error 'cv2.cv.cvseq' object has no attribute 'total'

I was looking for some image edge detection code in Python on the web and found some interesting stuff that I wanted to take a look at. Unfortunately I keep getting this error: 'cv2.cv.cvseq' object has no attribute 'total' The line of code at fault…
DamianJ
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find edge in image

How can I detect the edges in an image without using method 'edge', with only using mathematical operations (matrix or Derived or div or any other)? Indeed, how can I rewrite the function edge by using the algorithm Canny or sobel or any other?…
user1263390
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