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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: adaptive sobel-like edge detection

Please help! I have an image similar to the one attached (a gradient from dark to light moving south to north with a horizontal white line which is of interest) I am trying to look along each vector in the y axis starting from the bottom of the…
user3470496
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How to get better edges of moving objects when using frame differencing?

I want to track moving people in real-time by an SoC, so I use simple frame differencing(Image(n)-Image(n-1)) for extracting the foreground objects because of its low computational overhead. After extracting the foreground, matching is used to find…
williamCV
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Stop UIPageViewController at edge of screen

As I am swiping between two views, the views follow the finger and exceeding the edge of the screen and finally bounces back to the edge screen when I release my finger. Is there a way to make the views stop exactly at the edge?
vaid
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Find image edges in R plot

I have made image matrix with readTIFF (from tiff package), and I'm curious how image edges of basic shapes could be located in the matrix? The matrix contains intensity values, so the image represent is grayscale. I know that I could visualize them…
IP-84
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Prewitt operator implementation against MATLAB edge function?

Using conv2 I'm implementing Prewitt operator for edge detection. This is what I'm trying: b=[-1 -1 -1;0 0 0;1 1 1]/256; c=[-1 0 1; -1 0 1; -1 0 1]/256; Gx=abs(conv2(openImage,c,'same')); Gy=abs(conv2(openImage,b,'same')); G = sqrt( Gx.^2 +…
diegoaguilar
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Writing an application to compare the shapes of images (ex: what state does this potato chip look most like?) and would like some help getting started

I am looking to build an application for my boyfriend's birthday gift and would like some help getting started! I'd like to be able to input a photo (of a potato chip or something with distinct edges) and have the app select & output which state in…
Ashley C
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Edge following algorithm for OpenCV (c++)

In this book and this pdf I found a simple "edge following algorithm". This algorithm takes a seed-point on a edge as argument. Then the edge is tracked around the object until the seed-point is reached again. Is there any algorithm available to do…
Oliver Wilken
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what's the use of Edge Detection of image?

After getting edge image using canny, what's the use of edge image? Is there any use case of edge image? find object and Segment it from image? or get the sharp,area and perimeter of the object?
szbruce
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CIDetector to filter rectangle and get cropped image

I have an app which uses Tesseract for OCR. Till now I used to have a manual cropping option of image and then pass the cropped image taken from camera to Tesseract. Now in iOS8 there is CIDetector,using that I am detecting rectangle and passing…
Abhinandan Sahgal
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Unite endpoints of edge with line

I'm trying to make an object recognition program using a k-NN classifier. I've got a bunch of images for the training part of the classifier and a bunch of images to recognize. Those images are in grayscale and there's an object (only its edge) per…
user2952272
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Completing an image edge using MATLAB

I'm trying to complete the right edge of the large rectangle in the following image: The approach I've tried involves running a Sobel filter for edge detection on the image rotated by 45 degrees, following which I used the MATLAB Hough Transform…
prestojunkie
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Filter to replace edge points by a circle

I have the following HW assignment: Go to the "saw" image. Do edge detection. Now, by convolution, replace each edge point by a small circle or with a small Gaussian. Which filter can I use to perform this operation? Thank you! saw_image =…
Digital Da
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How to colour the edges after using sobel filter?

I am using sobel filter for edge detection. How to illustrate the gradient direction with color coding. For example, horizontal edges with blue and vertical edges with yellow? Thank you.
indu
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detect horizontal and vertical edges opencv

i try to detect very clear edges in my image. i tried different solutions with opencv( houghlines, sobel, laplace ) . But with all this algorithm i dont get the result i want. this is the image to detect the lines. the red lines are showing the…
Manul Hüttinger
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how to use 3x3 gaussian filter correctly

I am following a tutorial in image processing and it says the following From the gray-scale image, a Gaussian image pyramid PGauss is computed by firstly applying a 3× 3 Gaussian filter to the image I know how to down and up sample an image using…
rmaik
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