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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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Perform Canny Edge Detection twice --> better line-detection?

I'm working on a project with EmguCV (.NET-version of OpenCV) and I'm using the probabilistic Hough Transformation to find lines. So at first I was performing the canny-operator. Afterwards doing the Hough-transformation. Gray cannyThreshold = new…
lostprophet
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Python Large Image Edge Detection Using Scikit-image and GDAL

I have large file 9600x7000 pixel jpg file I am trying to see if I can do a edge detection. I tried loading the large (25Mb) file using: from PIL import Image image = Image.open("C:\\pathtofile\\test-tac.jpg") image.show() However python…
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Android: how to get good high and low threshold for canny edge detection using opencv

i am using opencv library for image processing process in android. The problem is when i use canny function for image. This is my code of using canny: Imgproc.Canny(ImageMat, ImageMat, 0.4, 0.5); i use low threshold 0.4 and 0.5 for high threshold,…
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Subscripted assignment dimension mismatch after vectorizing a loop

I tried turning this: for r=1:fsize for c=1:fsize mask(r,c) = exp(-(((r-centre)^2+(c-centre)^2)/2*(sigma^2))); end end into mask(1:fsize,1:fsize) =…
The General
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Hough transform line follower

Okay, I want to make a program to detect a line from a camera stream. This is for al line follower robot. So if the robot know the angle of two parallel lines, he knew in which way he must ride. I perform the follow functions: Make frame gray…
user3102712
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edge detection- how it works?

I am new to image processing and had to do some edge detection. I understood that there are 2 types of detectors- Gaussian and Laplacian which look for maximas and zero crossings respectively. What I don't understand is how this is implemented by…
Vaibhav
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Laplacian filter

I have been trying to apply laplacian filter in java. int red = 8 * red - imageOne.getRed(i - 1, j - 1) - imageOne.getRed(i, j - 1) - imageOne.getRed(i + 1, j - 1) - imageOne.getRed(i - 1,…
Ken
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kinect hand and finger tracking

As a part of my project I have to implement hand and finger tracking using kinect. From what i've read so far the basic method is: trace the contour of hand find finger tips using convex hull or k-curvature algo Is this correct? If it is can…
Vaibhav
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Matlab Image Edge Re-sizing/Thinning

So I am currently working on this project and I'm done with 90% of it and just need help with a particular question. So the setup is that when you perform a 2-dimensional convolution (using conv2) on the three color channels of a RGB image with the…
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How to create outline around text in bitmap Java

I load a ttf file and create a bitmap (256x256) with transparent background, I then draw the characters (font glyphs) on the bitmap. What I would like to do is create an thin (1 or 2 pixels) white outline around all the characters, maybe using edge…
Hank
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Finding contours after canny edge detection

I want to extract contours from a binary canny edge image. The original image is: After applying cvCanny() and cvDilate(), I get the following image: I need the enclosing box(the entire blue box) to be detected as a contour. I apply…
Hrishikesh_Pardeshi
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Best way to find vertical contours in a colored image

I want to detect only the vertical contours on an image like this: The standard method with canny detector gives back a poor result. (i prefer openCV API, but any idea would be helpful)
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Image Distortion with Lock Bits

I'm having a problem with writing to files using lock bits. I'm working on an edge detection software which has a strange distortion effect with most images. I've tried to isolate the problem, and it seems very random. It is not associated with…
vkoves
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Practical way of setting Canny edge detection algorithm parameters automatically

Canny edge detector is often used in many image processing tasks. However, in order to obtain a descent edge detection map carefully setting its parameters is very important. Based on my experience there are three important parameters: one is the…
feelfree
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How to increase continuance of edges detected by the canny filtrer

I have used a java canny detector from the public source. I wanted to detect edges of fibre in the image from microscope. But the result is kind of dissapointig. If you look at the result you can see that some edges are "doubled", we can see…
Yoda
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