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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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Running CannyEdgeDetector.java Example Java

Im trying to run CannyEdgeDetector.java example: This Example public static void main(String args[]) { BufferedImage img = null; try { img = ImageIO.read(new File("paper3.png")); } catch (IOException e1) { // TODO…
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How to perform DoG in opencv with java API

i just want to know which opencv with java API perforems the Difference Of Gaussian DoG?
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Sprite not staying on screen (left and right)

I am making a game with a Sprite that moves around the screen, I have created a collision for the edges using self.physicsBody = SKPhysicsBody(edgeLoopFromRect: self.frame) This seems to work for the top and bottom of the screen but the left and…
JMD
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How to resample an edge of an image in MATLAB?

I was trying to decrease the number of points of a detected edge of an image but I didn't obtain a good result. I want the result to contain exactly 200 pixels of the edges, but those points must be well chosen so the shape remain very clear. How…
Deep Blue
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Android edge detection on open camera

I've been looking into edge detection on Android and the examples I have found run the algorithm on a set image. I'm trying to use an edge detection algorithm to detect the edges on the camera app as you move the camera. I can't seem to find…
Rafa
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Does edge detection depend on image features?

Hi I am trying to figure out whether edge detection depends on image conditions (features). I know there is a huge mathematical basis for any edge detection operator. Also I know edge detection is sensitive for a noise on a picture. What about…
Vitali Grabovski
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python: inputting a negative value into array keeps giving me 256 minus that value (image- prewitt edge detection)

I am trying to do simple prewitt edge detection on an image and output 2 images with horizontal and vertical edges. For some reason, whenever the output value should be negative (for example -3), my output array ends up with 256 minus that value…
user3470496
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Error while calculating the edge of an image

I'm trying to extract edge from an image. I used the following algorithm.Input image(e11) which is a 512 * 512 grayscale image is also given. Find the morphological gradient of input image(gradientim) Find the negative image of the gradient…
Celine
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How to determine edges in an image optimally?

I recently was put in front of the problem of cropping and resizing images. I needed to crop the 'main content' of an image for example if i had an image similar to this: (source: msn.com) the result should be an image with the msn content without…
Sorin Antohi
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GLSL Fragment Shader: detect that the current fragment is on the edge of a polygon

I'm trying to write a shader that does antialiasing by reducing the opacity at the edge of polygons. So basically, if the fragment is on the edge of a polygon, divide the opacity by two. How can I detect if the fragment is on the edge of a polygon?
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opencv: How to detect rectangle with the not-in-order points in contours

In OpenCV we can use the approxPolyDP to find the contours of an object. However, sometimes the output contours could be quite different when there are holes/blur in between the lines. For example, the actual object of the following two graphs is a…
chesschi
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Assembling a Haar-like filter for edge detection

In the paper located at this link at "B. Detecting vertical edge using Haar-like feature" it mentions the use of a Haar-like kernel in order to obtain a resulting image which emphasizes vertical or horizontal edges in the input image the way the…
Ray
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find the edge based on normals

I have a 480*640 depth image, and I got the normals (a 480*640*3 matrix) of each pixel from this depth image. Does anyone know how could I find the edge based on the normal information? Thanks a lot!
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Compare two videos using Image processing

Hi i am new to image processing.I want to compare two videos using image processing.First type of video has effect(blur) in video.And second type is normal video. Using edge detection i want to compare two videos.So i want to use canny edge…
Sajith Vijesekara
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calculating the gradient of a 3D matrix

I have a 3D matrix and want to calculate the gradient for this matrix. The only step which I did is defining image gradient for a 2D image as follow: sx = [-1 0 1; -2 0 2; -1 0 1]; sy = [1 2 1; 0 0 0; -1 -2 -1]; Gx = conv2(input, sx, 'same'); Gy =…
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