Edge detection is the process of identifying points in an image, where image brightness changes sharply.

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24 views

Which correct sentence to explain the function $g(\nabla I)=\frac{1}{1+\beta |\nabla(G_{\sigma}*I)|^2}$

I have a edge indicator function that has formula as $$g(\nabla I)=\frac{1}{1+\beta |\nabla(G_{\sigma}*I)|^2}$$ where $\nabla$ is gradient operator, $*$ is convolution operator, $G_{\sigma}$ is a ...
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12 views

Detecting discontinuities in derivatives in images

Considering an grey-scale image as a function z=f(x,y). (Specifically, I'm interested in f=h∗h∗...∗h, where h is the indicator function of a regular hexagon.) I am interested in finding places where f ...
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2answers
48 views

Convolution theorem for “weighted” convolution?

Consider what I call a "weighted" convolution of a two-dimensional signal (image) with itself: $f({\bf r}) = \int d {\bf r}' \, g({\bf r}') s({\bf r},{\bf r}') g({\bf r}-{\bf r}')$ where $s$ is a ...
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1answer
22 views

How do I compute the gradient vector of pixels in an image?

I'm trying to find the curvature of the features in an image and I was advised to calculate the gradient vector of pixels. So if the matrix below are the values from a grayscale image, how would I go ...
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1answer
25 views

Detecting a smooth boundary with known shape in an image

I have designed a surface with a shape like a rounded rectangle and I want to detect its exact boundaries in a photo I take from it. A sample photo is like this: I have tried thresholding the image ...
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23 views

eliminating white areas without sharp boundaries

I have images of following type: and As one can see, in the corners of the images there are white areas which don't have sharp or well defined boundaries; the intensity gradually decreases. ...
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1answer
42 views

Help Understanding the Robert Cross Operator

I have been reading this Wikipedia article: https://en.wikipedia.org/wiki/Roberts_cross And it says this: Now I have also been reading this for the Robert Cross operator (from Feature Extraction ...
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15 views

Singularity Detection from 2D Wavelet Modulus Plot

I was wondering if I could get some tips/resources on how to pick out the singularity from my 2D Continuous Wavelet Transform Coefficient Plot (scalogram) using the Gaussian Derivative as the ...
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35 views

Edge Detection on small images

I just newly join to this community. Recently I work on edge detection that is applied on the attached picture. The objects that I want to detect are the white square images (there are 4 of them). So ...
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37 views

Sobel Filter Operatios

I have an image which has a vertical line which is 2 pixels wide and 4 pixels long and the remaining image is black. Now I want to find the edges in the vertical direction and for that I use the ...
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0answers
28 views

Completing an image edge using MATLAB

I'm trying to complete the right edge of the 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, ...
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31 views

Need Help how to remove unwanted edge detection

Hye everyone. Really need help. How to remove the branch that i circle in the image. What parameters i should use. Really appreciate your help.
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1answer
102 views

In opecv function Hough circles how does parameter 1 and 2 affect circle detection and how can i adjust them to increase accuracy??

http://docs.opencv.org/doc/tutorials/imgproc/imgtrans/hough_circle/hough_circle.html I'm using houghcircle function to detect circle.Problem is if i set minimum radius to null it detects wrong center ...
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2answers
135 views

What's the best technique to determine if the contents of two images are the same?

I need to run comparisons on the output of hundreds of frames of simple 3D-rendered characters. Perceptually, many of the frames are exact duplicates. Based on this, I assumed something like a ...
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0answers
86 views

Corner detection of image in Matlab

I'm trying to detect the corner of a binary image(boundary image)Function using Freeman Chain Code algorithm.Code for corner detection is taken from Matlab Central(function name is "chaincode") I ...
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79 views

Edge detection of image in matlab

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 ...
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0answers
45 views

How to straighten the edges?

Are there standard efficient ways/algorithms to make edges in an image more straight or axis-parallel (horizontal or vertical) ? I have images that look like this: This is part of a segmentation ...
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0answers
72 views

Non-maxima suppression of gradient image

I'm new to image processing, However I was trying to learn how to detect edges using Sobel filter I had obtained the image gradient in both X and Y directions successfully using Emgu built in ...
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1answer
107 views

Ridge finding in noisy 2D image

I'm using MATLAB, and have experience with it but not with this kind of problem. I'm trying to identify white lines in noisy 2D images such as the one below. I can separate the brighter ones just by ...
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21 views

SURF SIFT detection

Do you have any idea if the surf extracted or detected interest points belongs to the same objects? I explain: SURF descriptor account the orientation of ip based on edges intensities around it. In ...
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1answer
27 views

Tracking a Predefined Curve in a Series of Images

I have a series of images. I want to be able to draw a curve on the image and track the curve in the series. For example, in the figure below, the left image illustrates the original image at time ...
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60 views

Creating graph from edges, shape detection

I am writing a shape detection program (for example, I make a triangle with fingers and algorithm finds it). My idea was to detect edges, "straighten" them, create graph from all the segments and ...
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2answers
80 views

Laplacian Operator with and without diagonal direction

This is a general question on the laplacian operator, which has two different versions. The first version is : \begin{matrix} 0 & 1 & 0 \\ 1 & -4 & 1 \\ 0 & 1 & 0 ...
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2answers
567 views

Rectangle detection in “real life” images

I have seen a lot of posts here and on SO and on various websites, using Matlab, OpenCV, name it, on how to detect rectangles in an image. I have done it myself too, using Matlab. My usual steps were: ...
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46 views

Image Processing - Identifing/locating Random Solid Blocks of Colour

I am not overly familiar with image processing. I know a little about it from University, but I have not really done any for a while and I have found myself with a problem that requires it. What I ...
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1answer
200 views

What's the state-of-the-art algorithms in image edge detection?

There are several state-of-the-art algorithms in image denoising including Non-Local Means, BM3D and so on. I am wondering whether there is some well-known state-of-the-art algorithms in image edge ...
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178 views

Visual regression test - Extract elements of GUI-Screenshot - MSER OpenCV

For a visual regression test I need to compare screenshots of webpages (different release-versions). I started with pixel by pixel compare. Actually I split the screenshot in different parts (maybe ...
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1answer
456 views

An alternative algorithm for blob detection

Here's a sample image of my experiment which is to be processed for finding the information of all the blobs (centre, dimension etc.). Basically the image contains some noise, few bold lines, and of ...
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19 views

Need to batch detect, measure, calc DPI for a consistently placed ruler in large set of technical images

I have a large set of photographs of pieces of rocks. In each photo there is a 4 inch ruler bar placed next to the rock, consistently on the left near the edge, see example: Over 10 years the ...
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66 views

Edge-preserving smoothing

I'm searching for a method that can smooth a 3D volume whilst preserving the edges in my volume. I researched anisotropic diffusion filtering and bilateral filtering but I'm having trouble to evaluate ...
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0answers
41 views

Optimal way for curve detection

I am totally new to image recognition and image analysis and have a project concerning detecting a smooth curve on a uniform background (white/black/any color) and then be able to follow this curve ...
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2answers
91 views

Edge detection on a color image

I understand the process of using a Sobel kernel for edge detection in greyscale images. The input is a greyscale image, and the output is a greyscale image. I'm having trouble, however, figuring out ...
2
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0answers
67 views

Detecting blades of a wind turbine

I have many close-range images of a single wind turbine blade (taken from different positions, same angle): I need to separate the blade image from background like this: The problem arises in ...
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1answer
52 views

Why are 2nd order edge detectors such as Laplacian more susceptible to noise?

I've been told that they are influenced by noise considerably more than that of a first order edge detector such as a Gaussian. But why?
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1answer
443 views

Algorithm for finding length and end points of a curly human hair

I'm trying to do some analysis of a curly human hair on an iPhone app. I've been using the openCV library. Particularly I want to be able to estimate the length of the hair, and locate its end points ...
2
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1answer
714 views

How to trace the edges on matlab

I am doing my Bachelor's project on Road extraction. I have detected the line segments(edges) in the image using hough transform. I need to detect the curved lines in the road and link them(edge ...
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2answers
119 views

detecting “deformed” lines

I have a project in which I have to recognize 2 lines in different "position", the lines are orthogonal but can be projected on different surfaces. I'm using opencv. I'm not asking for code, ...
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3answers
223 views

Which sigma to use for edge detection

I know that in many edge detection algorithm the first step is choosing a scale to work on. We actually operate on the chosen scale by applying a gaussian blur on the original image. I wanted to ...
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2answers
62 views

Is it feasible to try and classify an enclosed space as being a. Very crowded b. Less crowded & c. Sparsely crowded using image processing?

The idea is to get three classifications for crowd: High, low and medium based on an image captured inside a train compartment. Something like this: This gets classified in the 'High' category ...
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2answers
2k views

How do convolutions become matrix multiplications?

I know this question may not be very relevant to programming, but if I don't understand the theory behind image processing I'll never be able to implement something in practice. If I got it right ...
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1answer
418 views

Keypoint orientation with the oFAST from Rublee's ORB

I've just read the papers from Rublee et al. (ORB: an efficient alternative to SIFT or SURF) and Rosten et al. (Machine learning for high-speed corner detection) (=fast-detector). Rublee tries to ...
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1answer
236 views

best robust feature detectors for detecting similarities among archeological signs

I would like to implement edge detectors for creating a feature vector for archeological signs. Which are best features, algorithms to retrieve? That could be loaded in a Support vector machine for ...
2
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0answers
81 views

Finding optimal detectors by numerical optimization (Canny)

In "A Computational Approach to Edge Detection", John Canny explains that the optimal "detector" for finding step edges profiles in an image via convolution is a non-closed-form function closely ...
3
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2answers
412 views

Why is Prewitt filter High Pass

Prewitt filters are popular filters in image processing for edge detection http://en.wikipedia.org/wiki/Prewitt_operator Can anyone give a proof on why Perwitt and other edge detecting filters are ...
4
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1answer
790 views

Difference of Gaussians

I use the following formula for DoG: $$\frac{1}{\sigma} (\frac{x^2}{2\sigma^2}-1.0) e^{\frac{-x^2}{2\sigma^2}}$$ What is the relationship between this formula and the difference of two Gaussian ...
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1answer
4k views

Differences between OpenCV Canny and MatLab Canny?

does anyone know why the MatLab Canny (MLC) is so different compared to the OpenCV Canny (OCC)? ML-C delivers precise and more connected edges than the OCC, but how is that possible? The reason why I ...
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6answers
4k views

Image segmentation issue of different materials

Hi CV/Pattern Recognition Community, I've got a serious problem regarding the segmentation of an image. The scenario is an atmosphere within a furnace which makes my head go insane. And I need to ...
3
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1answer
5k views

EmguCV: Detect a ball in the frame

I am having a VERY hard time capturing when the ball comes into frame in this video http://www.youtube.com/watch?v=x1V6_OHrXIo I have no idea what to set the parameters too, and trying random values ...
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1answer
98 views

learnable segmentation or learnable edge detection

Is there some learnable segmentation or learnable edge detection algorithm exist? For example I mark N fotos by hands and than program "learns" how to do it best way and can do it on similar images. ...
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2answers
5k views

Straight lines with an edge detection algorithm

I've been thinking of an algorithm for object recognition but it would relies heavily on straight non-noisy lines and as far as I know this is hard to obtain with edge detection algorithms. What's the ...