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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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MATLAB, algorithm for free surface detection in bubbly flow

I am trying to figure out an algorithm for detecting the free surface from a PIV image (see attached). The major problem is that in the flow under consideration gas bubbles are injected into the fluid, these rise up due to buoyancy and tend to sit…
Fryderyk
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Assign edge pixels to lines of interest

I am dealing with image processing using Matlab and my goal is to assign pixels to a characteristic line of an object. In detail: I take pictures of different metallic objects. I can distinguish the objects in 6 different classes. The classes are…
Igor
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php - how to find coordinates of edges in an image using imagick or other library?

given an image composed of a plain black field with a single white rectangle inside it somewhere, how can i extract the coordinates of the rectangle ? i've googled and googled and found numerous articles on edge detection using hough lines,…
david furst
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Edge detection in Java on a PPM using the Sobel Operator

I am trying to do edge detection, using the Sobel Operator, and I am getting a weird triplicate image. The image starts life as a PPM, which I am storing as a multi-dimension array of Color's: I convert it to grayscale, which seems to work just…
Tim AtLee
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Draw Rect around result of canny edge

I want to draw Rect around detected canny edges. I have this image which is result of eye detection, morphological operations and canny edge. I tried using contours to bound it by rect but result was not accurate. How can I get some thing like this…
musta
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Finding the edge of the picture in MatLab

I am trying to find coordinates of edges of the image (a rectangle, basicly) formed by this code: %Pre-setting Variables N=300; M=300; H=80; L=100; Alfa=10; Tx=20; Ty=20; Tz=10; Sx=0.6; Sy=0.7; Sz=1.2; Tetax=20; Tetay=30; Tetaz=20; % Forming…
Evgenyj Afanasyev
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Detecting edges of lasers/lights in images using Python

I am writing a program in Python to loop through images extracted from the frames of a video and detect lines within them. The images are of fairly poor quality and vary significantly in their content. Here are two examples: Sample Image 1 | Sample…
Richard
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Edge Detection in Image Processing using VHDL

I am very new to the image processing field. My question is that 1) In edge detection, which filter is used for real time purpose?
PRIYA
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opencv structured forest edge detection and findcontours

I am trying to use opencv via visual c++ to extract contours of an image. I was able to do that using the opencv tutorial for findcontours. findcontours works in two steps Detect edges using canny edge detector. Feed the output of canny to…
Subu
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opencv homography of nonlineer papers

I want to get the homography matrix for images whose edges are not linear. I have a solution for linear edges, but I want to rectify cases of non-linear edges. I can detect edges and corners of image with code, but need to construct lines that are…
Alican OZER
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Tips on building a program detecting pupil in images

I am working on a project that aims to build a program which automatically gives a relatively accurate detection of pupil region in eye pictures. I am currently using simplecv in Python, given that Python is easier to experiment with. Since I just…
wenxi
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Canny edge detector with a single threshold value

I'm trying to port some Matlab code to C++. I've come across this line: edges = edge(gray,'canny',0.1); The output for the sample image is a completely black image. I want to reproduce the same behaviour using cv::Canny. What values should I use…
protas
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contour line edge detection in MATLAB

I have a project to detect the contour lines in image , but when I run my code with the canny edge detection algorithm , one line in the image transforms to two lines, because of two times the change in grey values of the line before and after…
saleh shahhoseini
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Finding the edges of a partial ellipse in an image

I have an binary image as shown below. As can be seen in the image there is an edge which looks like an arc of an ellipse, as illustrated below and I manually marked it as red. These red pixels should be found by the code. My goal is to fit an…
afp_2008
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not-threshold-ed value of edge detectors in Matlab

It is possible to perform a variety of edge detector filters in Matlab, using edge function. But this function applies a threshold on the output. Is it possible to disable such thresholding? If not, is there any other ways to calculate the original…
Hamed
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