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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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Gradient Direction in Canny Edge Detection

I am trying to understand the concept of Non-maximum suppression(Canny Edge detection), So I started looking at the matlab code. The part of matlab code to determine the direction of the edge is shown below. switch direction case 1 idx =…
Nrupatunga
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Java : image processing - how to get set of images to same standard

I need to develop the simple skin disease diagnose system using image processing and neural network. To use images in neural network, image should be same standard and, To identify the skin disease we should apply some image processing technique as…
user3565768
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Edge Detection with Gauss Filter

I have a grayscale image in which there are edges that follow the right half of a Gaussian curve i.e. the intensity decreases from a local maximum to a local minimum following the Gaussian curve over a range of pixels. The mean is 0 and standard…
Umair
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directional edge detection in OpenCV

I would like to detect edge that has certain angle/orientation. Adapting from a post in SO, I've figured out to use OpenCV magnitude, phase and Sobel functions to filter out unwanted edge points. Then use the magnitude image (with phase image as…
TSL_
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How to determine isotropicity of a given edge detector

The isotropicity definition clearly states uniform response on all orientation; hence, on images, the brightness magnitude should not be different for different dimensions. However, it is not clear for me how to test a given edge-detector-function…
ahmet
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MATLAB - Find local maximum and minimum of an edge map (row-wise)

I'll start off by saying I'm new to MATLAB, and this is the first time I'm trying an application related to image processing. I'm building a MATLAB library (which is to be used in a Windows Phone Application), which takes in an edge map of a…
LahiruAgAr
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Display binary image using image command

i'm trying to display edge image(using Canny edge detector) in axes(axes4). The code below work out, but somehow the edge image is displayed in blue-ish axes(handles.axes4); imh=image(CannyImage1); resultImage=CannyImage1; axis off; axis…
user3606613
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apply the edge detection in an image segmentation

I have two questions about snake edge detection. The first question is, in openCV there is a function cvSnakeImage(src,points,.......), what does the points parameter mean? The second questions is: I want to apply this function on the part…
user3504947
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Showing three different edge images in single figure for comparison (No Subplot)

Hello friends, I have applied Canny edge detection to three different images and I got three images of edges of circles of three different sizes. I want to show these three edges of circles of different radius in same figure but with…
user3065109
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OpenCV c++ code for mexican hat operator

Can any one help me to find the Open CV c++ code for Mexican hat operator. I need the code for detecting the license plate. Please help me.
user3559863
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Hysteresis in Edge Detection

What the hysteresis threshold, and why is it useful in edge detection? I am trying to write an edge detection program in python, and it seems to work well without using hysteresis, but many sources include it. I was wondering why it would be useful.
user3558736
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Link missing (by Canny) edges

I need to detect all rectangles in image. Here is my code: Mat PolygonsDetection(Mat src) { Mat gray; cvtColor(src, gray, CV_BGR2GRAY); Mat bw; Canny(src, bw, 50, 200, 3, true); imshow("canny", bw); morphologyEx(bw, bw,…
Rougher
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Edge magnitude (Vertical and horizontal edges)

I want to join the vertical and horizontal edges together to get all edges in an image in order to use it for the Harris Corner detection. I'm using Sobel filters to get vertical and horizontal edges: I = imread('CleanFingerprint.jpg'); // read the…
N4LN
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How to get coordinates of end points in Cartesian coordinate system and the corresponding (rho,theta) in polar coordinate system of line segment

I have used Canny method to get edges of a image.Then I applied the approxPolyDP method to approximate edges,and got a set of polylines (not polygons) and line segments.Each polyline is formed from line segments.My purpose is to get coordinates of…
just_rookie
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straight line detection from a image

I am doing a project which is hole detection in road. I am using a laser to emit beam on the road and using a camera to take a image of the road. the image may be like this Now i want to process this image and give a result that is it straight or…
user1960072
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